260
Ind. Em. Ct”. Rod. Res. Dev. 1981. 20,260-270
REVIEW SECTION SuHlllmlnes. Synthetic Applications and potential Utilizations
Synmetlc procedures for various sulfiiimines, Mew chemical propertles. and numerous reactions for sulfilimines, useful for organic synlheses. are summarized in Mis compact review, which also deals with the potential utilizatbns of sulRlimhes and the related derivatives both in organic syntheses of fine chem lcals and industrial uses.
Naomicbi Furukawais associate professor of organic chemistry a t the University of Tsukuba. After he obtained his B.Sc. from Kyoto Uniuersity in 1960, he joined the Chemistry Department of the Radiation Center of Osaka Prefecture where his association with Professor Oae began. In 1963, he mooed to Osaka City Uniuersity where he obtained his Ph.D. in 1968 and then came to the Uniuersity of Tsukuba as an associate professor in 1974. He also spent one and one-half years at Brookhauen National Laboratories in the late 1960’s. He is the author of about one hundred scientific papers, mostly on organosulfur chemistry. ~
I
Introduction With the rapid increaae of organosulfur compounds (I), their industrial applications have expanded widely in the fields of dystuffs, medicinals, agrochemicals, detergents, solvents, and numerous other industrial materials. Especially remarkable was the rapid growth of chemistry of sulfoxide and related derivatives which have received considerable attention. Sulfilimine (I), a nitrogen isoelectonomer of sulfoxide (2), is a relative newcomer but is receiving considerable attention in recent years, together with its derivatives, such as sulfoximine (3) and sulfonediimine (4). both being isoelectronic to sulfone (5), and
1
2
w 1
NH I
3
4
6
several convenient synthetic procedures for sulfilimines, their chemical behavior and synthetic applications for organic syntheses have been explored extensively. A few reviews have already covered some of the chemistry of sulfilimines (2); however, the rapidly growing field of chemistry has prompted us to write another new review now. N-p-Tosylsulfilimine (I) was first prepared in 1921 by Nicolet and Willard (3) by simple treatment of sulfide, R-S-R’,with chloramine-T CTsNClNa.3H20) in methanol at room temperature. Most N-p-tcaylsulfilimines (R3 = Ts = CH&H,SOJ are crystalline and hence many liquid sulfides were converted to the corresponding crystalline N-p-tosylsulfiliminesfor identifications or characterizations (4) much the same as the chemical transformations of liquid aldehydes and ketones to the corresponding crystalline oximes and hydrazides. While the structure of a simple sulfilimine, i.e., N-ptosyldimethylsulfilimine, was determined explicitly by X-ray crystallography (5)dipole momenta (6),preparation of optically active compounds (7)and thermal stabilities (8) of several sulflimines have also been measured. These studies revealed that sulfilimines are of pyramidal structure, similar to sulfoxide and sulfonium ylide, while the S-N bond is semipolar. Because of the thermal stability, 0198-4321/81/1220-0260$01.25/0
Shigeru Oae is professor of organic chemistry a t the Uniuersit: of Tsukuba. Oae obtained a B.Sc at Waseda Uniuersity and a D.Sc in chemistry at Osaka University where he was a staff member fo, nearly ten years. He then spen, most of the 1950’s in a few aca demic institutions in the U.S., in cluding the Uniuersity of Kansas Uniuersity of Pennsylvania, anL Drexel Institute, where he was a n assistant professor, and Brookhauen National Laboratories, before he went back to chair the Chemistry Department of the Radiation Center of Osaka in 1960. He was professor of Organic Chemistry a t Osaka City Uniuersity from 1962 to 1973 and then moued to the newly created Uniuersity of Tsukuba to organize the Chemistry Department. He is a n author of about fiue hundred scientific papers, 15 books, including “Organic Chemistry of Sulfur” and “Sulfur Bonding”, and is known as one of the leading organosulfur chemists. He was Vice President of the Japanese Chemical Society and currently is a visiting professor a t the Department of Chemistry of the Uniuersity of Kansas. many optically active sulfilimines have been synthesized. The thermal stability of the sulfilimine, as measured by the rate of racemization, falls in between those of two other isoelectronomers,Le., sulfoxide and sulfonium ylide, relative rate being 10’’(sulfonium ylide):1O6 (sulfi1imine):l (sulfoxide) (8). However, since the electronic nature of sulfilimine is similar to that of sulfoxide and sulfonium 8 I981 Amsrican chsmlcal SOCW
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 2, 1981 261
ylide, one may expect much similar chemical behavior of sulfilimines to that of sulfoxides and sulfonium ylides which have been so useful in many important organic syntheses in recent years (9). Indeed, there are many analogous reactions with sulfilimines common to those of the other two sulfur isoelectronomers, such as facile pyrolytic Ei reactions (IO),oxidation reactions, etc., whereas there are many more reactions which are observed specifically only with sulfilimines such as thermal Curtius rearrangement of N-acyl sulfilimines (1I), formation of aziridines in the reaction of N-unsubstituted sulfilimines with electrophilic olefins (12),etc. As the specific nature of sulfilimines is more clearly understood, many more useful reactions are going to be discovered. Among numerous sulfur compounds containing S-N linkage, S2N2,S4N4,and related (SN), compounds are receiving much attention today (13). Bright orange-colored crystalline N4S4 can be obtained by first saturating a carbon tetrachloride solution of S2Clzwith C12 and subsequent treatment with ammonia. Thermolysis of S4N4 at 300 OC gives colorless N2Szwhich when kept at 20 OC gradually changes to polymeric -(SN),,-. This polymeric -(SN),- is a metallic crystalline substance which is diamagnetic and has a rather low electric resistance. Its IR stretching frequency of S-N linkage appears at 1225 cm-l, which corresponds to 1.48 A of S-N bond as against ca. 960 cm-' for average S-N linkage of common N-p-tosylsulfilimines. Each unit of S-N linkage in -(SN),- compounds has three electron pairs, which are delocalized as shown below, signifying the molecule to be a good electric conductor. In fact, the polymer pellet (2 mm diameter, 5 mm length) gives a constant value of electric resistance under pressure of about 20 kbar. Under a pressure of 60 kbar, the electric resistance falls as low as 0.02 ohm. Thus, the polymer has a bright future as a potential superconductor.
If the sulfur atom of this polymer would be either alkylated or arylated, the polymer would become suilimine or sulfondiimine ( I 4 ) , derivatives, depending upon the number of alkyl or aryl groups on the same sulfur atom. The electric nature of those hypothetical derivatives would also be fascinating to examine. Unlike the -(SN),- polymer, not many industrial applications have been developed for sulfilimines due mainly to the limited amount of research and development. However, some of the derivatives have been shown to be good herbicides while others are known to be excellent tranquilizers, besides being used as rather reactive intermediates for making fine chemicals despite their young history. Applications of sulfilimines in the future appear to be found in two directions, i.e., direct use of sulfiliines and related derivatives for fine chemicals such as drugs, herbicides, etc., or special chemicals to be utilized for organic syntheses. 1. Preparation of Sulfilimines Most sulfiiines, shown by formula 1 are crystalline and several synthetic procedures have been found even for N-unsubstituted (free) sulfilimines (R3 = H).A few representative sulfilimines are selected and their synthetic procedures are listed in Table I. These procedures are broadly divided in two general processes. The one involves treatment of sulfide with halogenating reagents together with amino derivatives, while the other treates sulfoxides with amino derivatives in the presence of condensing agents. The processes are
Table I. Preparation of N-Substituted Sulfiiimines
R'-s-R~
1
NR3
R'
RZ
Me Me Me Me Me Ph Me Me Ph
Me Me Et Ph p-MeOC,H, Ph Me Ph Ph
R3
mD. "C
MeSO,
122-123 158-159 133 132 145 113
p-TolSO, p-TolSO, p-TolSO, p-TolSO, p-TolSO, MeCO PhCO MeCO
67-68
104.5-105 86-87
conveniently used in both small-scale and large-scale preparations. 1.1 Treatment of Sulfides with Halogenating Agents and Amino Derivatives (15). The most general procedure involves treatment of sulfides with chloramine-T (a chlorinating agent having a built-in amide group); it is called the Mann-Pope reaction (4). This reaction has been used extensively to prepare various N-p-tosyl and other N-sulfonyl sulfilimines. One drawback of the original Mann-Pope reaction is that the yields of N-p-tosyldiarylsulfilimines are quite poor. However, upon careful kinetic studies, it has now become the most convenient method to prepare sulfilimine of any kind in an excellent yield by just adjusting the reaction medium (usually methanol) slightly acidic with acetic acid (16). R'
R2/\S
1
4- R3S0 2
"OH LNaw
R\S--cNS02R3 R2'
(1)
There is one exceptional case. Sulfides having an active methylene group are occasionally halogenated with chloramine-?' at a methylene group besides being oxidatively iminated on a sulfur atom. Since chloramine-?' usually has crystalline water, formation of sulfoxide as a byproduct is observed. One way to avoid the sulfoxide formation is to use dry chloramine-?' (which, however, could explode in rapid drying) in such an aprotic solvent as methylene chloride. Another way to improve both yield and the quality of sulfilimine is to run the reaction under the phase transfer condition using a catalyst such as tetrabutylammonium bromide (17). Other N-haloamides such as N-chloro- or bromo acid amides, N-chlorourea, and N-chloroamidine also react with sulfides in the presence of a base to afford corresponding sulfiliminesin decent yields (18). In the reaction of saldes with such halogenating agents as t-BuOC1, N-chlorosuccinimide (NCS), and N-bromosuccinimide (NBS)in the presence of acylamides or amines, numerous N-substituted sulfilimines have also been prepared. One such example with NCS is
R' S '-NR3
(2)
R2'
1.2 Condensation of Sulfoxides with Amine Derivatives. One of the two general procedures involves the
262
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20,No. 2, 1981
initial formation of reactive oxosulfonium salt by treatment of sulfoxide with an electrophilic reagent and subsequent reaction of the oxosulfonium salt with some aminating reagent (20). Another procedure is one step treatment of sulfoxide with arenesulfonylisocyanate or disulfur-p-tosyldiimide (7bJ'l). Both are excellent processes to afford various sulfilimines in good yields.
X'Y-; (CH,CO),O, (CF,CO),O, P,O,, POCl,, DCC etc. R'
S ' -0
R2/
+
R3WX=Y
-
R'
'S-NF?'
t O=X=Y
(4)
R2'
R3: RSO,,RCO, X = Y = CO, SO; S = NS0,R3 etc.
Photolysis of sulfonylazide or acylazide with sulfides also gives N-sulfonyl or acyl allylsulfilimines, apparently via forming sulfinyl- or acylnitrene (22). Some N-alkylsulfilimines were obtained by treatment of certain sulfuranes with alkylamines. However, reactions are not suitable for large-scale preparations though they are quite interesting reactions. 1.3 N-Unsubstituted Sulfilimines. N-Unsubstituted sulfilimine was first synthesized by Appel et al. (23) by treatment of dialkyl sulfides with either hydroxylamine0-hydrogen sulfate or chloramine-ammonia, however the methods are by no means convenient since either the reagent used is unstable, or the yield is generally poor, especially with aryl sulfides. Because of the tremendous potentials for synthetic applications, convenient syntheses of N-unsubstituted sulfilimines have long been desired. The following two useful procedures have recently been developed for the synthesis of N-unsubstituted sulflimines by two Japanese groups independently. (1) Cleavage of Tosyl Group of N-Tosylsulfilimines with Concentrated Sulfuric Acid (24). Ph2S-NTs + conc. H2S04
+
-
NaOH
[ P ~ ~ S - N H ~ T S O - ] Ph2S-NH (5) This reaction was discovered by us and involves only mixing N-p-tosylsulfilimineof any kind with commercially available concentrated sulfuric acid for few minutes, subsequent neutralization of cold aqueous solution of the reaction mixture, and final extraction with chloroform. Diarylsulfilimines can be obtained nearly quantitatively and are stable, while dialkyl- and alkylarylsulfiliminesare also prepared by careful neutralization with ammonia but are rather unstable and decompose to yield mainly sulfoxides unless they are converted to such salts as picrates. Since none of the reagents used is expensive while the reaction proceeds so readily, this process can be used for large scale-productions of various sulfilimines. (2) Reaction of Sulfide with N-(Mesitylenesulfonyl)hydroxylamine.
for Lab-scale synthesis of N-unsubstituted sulfililimines but may not be applied for a large-scale production since MSH has to be prepared through several steps and hence is not cheap. A few representative examples are listed in Table 11. 2. Reactions of Sulfilimines. Synthetic Applications There are the following three main directions in organic syntheses: (a) synthesis of target molecule through simple treatment under mild conditions; (b) synthesis of target molecule in as few steps as possible, yet in a good yield; ( c ) specific either stereo- or regio-controlled synthesis of target compound. Many organosulfur compounds have been utilized for this purpose, using their characteristic features, such as the strong nucleophilic cite of thiols and sulfides, facile formation of reactive a-sulfinyl or sulfonyl-carbanions, readily feasible C-C bond formation through condensation with these a-sulfur-stabilizedcarbanions, and easy removal of sulfur-containing leaving groups from the product to give final target compounds (9). Both sulfoxides and sulfonium ylides hav e been used extensively as building blocks for synthesis of complicated molecules. Sulflimines are also expected to serve for the same purpose and would be more useful since the preparation is simple while most sulfilimines are crystalline, nonhygroscopic and yet freely soluble in most solvenbs. Then what kinds of useful reactions have been known with various sulfilimines? 2.1 Olefin Formation through Pyrolysis (Ei Reaction). N-p-Tosylsulfilimines are relatively stable and easily accessible through our modified Mann-Pope reaction. N-p-Tosylsulfilimines bearing a P-proton, however, undergo facile thermal decomposition at around 80-100 "C, affording N-p-tosylsulfeneamide and corresponding olefins via five membered transition state of the Ei reaction, as shown below (26).
-
Ph--S-CH2CHzR
1 NTs
[Ph--S--CH2-
1
c H-Rl
"UH (7)
PhSNHTs t CH2=CH---R
Our careful mechanistic studies have revealed thatthe rate of pyrolysis of the sulfilimine is substantially higher than that of the analogous sulfoxide and nearly equal to that of the N-oxide (27)(Cope elimination). The reaction is extremely stereoselective as shown by the following thermolyses of the erythro- and threosulfilimines (6) (28). Ph 80 'C 5 h
Me0
Ph
100%trans
ery thro-6 Ph
80 O C 5 h
Me0 OM e
Ph
5% trans
Me0
H
94.5%cis
threo-6
This procedure, found by Tamura et al. (25) involves mixing simply sulfide with N-(mesitylenesulfonyl) hydroxylamine (MSH), prepared in advance and subsequent treatment with an alkaline base. It is a convenient method
The rate of the Ei reaction of N-p-tosylsulfilimines is generally ca. lo2 times higher than that of corresponding sulfoxide. Currently, the most popular procedure for the tailor-made olefins is the pyrolysis of selenoxide because of the extremely facile decomposition of alkyl selenoxide (29). In fact, most alkyl selenoxides having @-protonsare so unstable that olefins are generated just by oxidation of
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 2, 1981 263
Table 111. Preparation of Isocyanates
Table 11. N-Unsubstituted Sulfilimines (R'R'S-fNH)
R'
RZ
Me Ph Ph Ph Ph Ph Ph a
yield, meth% od
mp, "C
p-To1 Ph Ph o-To~ p-Tol p-NO,C,H, p-NO,C,H,
20(158-159)a 71 71 83.5-84.5 54-54.5 98-99 93-94
95 75 90 97 90 95 90
CHFCH-CHzCH3
+
RNCO
NCOR
R
yield, %
adamanty 1 mesityl CH,
34.7 90.4 98.8 97.6 95.5 67.5
1
2
the selenides under cooling and the selenoxides cannot be isolated. One drawback of this reaction is that seleno compounds formed as byproducts are usually quite toxic and may not be recommended for routine organic syntheses. Orientation of olefin formation in the Ei reaction of N-p-tosylsulfilimine varies somewhat with solvent used. In the pyrolysis of N-p-tosyl-sec-alkylsulfilimine (7), the
-
A
I
1 1 2 1 1
Parenthetical value is the melting point of picrate.
Ph-I/1:iy3
-
Ph-S-Ph
CH3CHzCHCH3 (8)
drogen, such as N-p-tosyldiphenylsulfilimine are stable even under heating above 200 "C. However, N-acyldiphenylsulfilimines (10) pyrolyze below 200 "C to afford diphenyl sulfide and corresponding isocyanates quantitatively via a Curtius-type rearrangement as shown eq 12 (33)
&I
ct '
m.c %
W2S-NCOR
10
-c
4 s
NTs
+
(12)
RN=C=O
11
7
neat 115-120 "C neat 160-170 "C Me,SO 115-120 "C C,H, 115-1 20 "C
2.0 1.7 1.5 0.67
1.0 1.0 1.0 1.0
amount of 1-olefin exceeds that of 2-olefin in Me2S0, whereas exactly the opposite ratio was found in the pyrolysis in benzene (27). An a- or 6-phenyl group or any other electron-withdrawing group at a and @ positions was found to accelerate the rate of the pyrolysis. An a-phenyl-substituted derivative was found to undergo Ei reaction even at room temperature. Since the stereoselectivity of this facile Ei reaction is so high, the reaction is regarded as one of the best ways to prepare tailor-made olefins. Indeed, this procedure has been utilized in introducing a double bond in organic syntheses, some of which are shown in the following three examples. ,MP
9
8 NTs
I
(ref 31) (10) h
Photolysis likewise gives nearly the same rearrangement product together with diphenyl disulfide but the yields are substantially lower than those in the thermolysis, due mainly to the side reactions. Since N-acylsulfilimines (10) can be readily prepared by treatment of N-unsubstituted diphenylsulfilimine with various acylating agents even including lactones and thiol esters, while the separation of diphenyl sulfide and the isocyanate is achieved very easily, thermolysis of N-acylsulfilimines is an excellent process for preparation of any desired isocyanate. A few typical examples are listed in Table 111. There are possibilities that some N-acylsulfilimines, formed by acylation with lactones, thiolactones, may give heterocyclic products directly upon thermolysis as some of our preliminary experiments have already shown. Meanwhile, diphenyl sulfide, recoverable quantitatively, may be used repeatedly by conversion to the sulfilimine. Incidentally, the seleno analogues N-acyldiphenylselenilimines, undergo much more facile thermal rearrangement, even at around 160 "C, affording isocyanates nearly quantitatively (34). The thermolysis can be carried out either in neat or nonpolar media such as benzene and tetralin, while some of isocyanates formed may react intramolecularly to afford cyclic urea or urethane derivatives or intermolecularly with alcohols or thiols present, forming urethanes or thiocarbametes by which active OH or SH group can be masked. Pyrolysis of N-thioacylsulfilimines (12) yields nearly quantitatively the corresponding nitriles along with elemental sulfur and is presumed to proceed via the route shown by eq 13 (35)
-
Ph$-NC(S)R
[PhzS---N-
12
-Rl
S
be
Thus, this Ei reaction is a convenient process for preparation of olefins of desired geometries, and it will be used more extensively even in industrial productions. 2.2. Synthesis of Isocyanates by Thermolysis and Photolysis of N-Acylsulfilimines and Related Reactions. Sulfilimines, bearing no alkyl group with P-hy-
ci -
PhzS i[R-Cd-Sl
R
Ph
yield 95 (%)
nitrile
p-To1 93
+
13 m-To1 p-MeOC,H, 96
97
R-CN
+
S,
(13)
m-MeOC,H, 95
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20,No. 2, 1981
284
Following are a few examples of thermal intramolecular cyclization to form heterocyclic compounds by pyrolyses of respective N-substituted sulfilimines (25, 36)
Thermolysis of N-p-tosylmethylphenylsulfiliminein MezSO at 180 "C gives not only unsymmetrical methyl phenyl disulfide and symmetrical diphenyl disulfide but also p-tosylamide and a small amount of polymethylene oxide and is considered to proceed via the route shown by eq 15 (37)
+
Fh-S-Me
Me,%
PhSSMe t PhSSPh
1NTs
(40%)
+
(CH,O),
+
(30%) (CH20)
14
-
[Ph-S-CH;-NHTs!
0 Me+0
bhS,C-, -KR
(21 1
usually takes place so readily upon gentle heating that the method is useful for introducing amino group regioselectively at the y position, as shown by 19 in eq 22.
I NTs
PhCH-CH=CHZ I
I
Ts’
-
-
z
1 18
PhCH CHCH2-S-Ph
H
CHzSR
I
S-R
/N\
N
(22)
‘S-Ph
yield,
CH, Ph CH3 Ph CH3 CH3 Ph CH, CH3 CH, Ph
H H 4-CH, 4-CH, 3-CH3 t 5-CH3 4-C1 4-c1 3-C1 + 5-Cl 6-C1 4-COOC,H, 4-CN
90 --
anilines, X H H P-CH, P-CH, m-CH,
p-c1 P-Cl m-Cl Ph-$H--CH=CHZ
R
X in product (1)
0-Cl
p-COOC,H, p-CN
%
61 54 63 86 83 68 87 70 65 73
Table V. Preparation of Allylamines
19
~
This reaction has been applied for preparations of various primary amines, from ketones or aldehydes and thiols with chloramine-T via formation of vinylic sulfides as illustrated by eq 23 (42). A few synthetic examples are listed in Table V.
carbonyl compd
1(“
vinyl sulfide (5%)
T
0
SPh
eo
h +
~~
allylamines (%)
(92)
NHTs (69)
(68)
NHTs (84)
(86)
NHTs
(79)
NHTs (80)
12;
Table VI. Preparation of Vinyl Sulfides
R
(23)
20
2.5. Vinylic Sulfides from N-p-Tosylsulfilimines. N-p-Tosylalkylphenylsulfiliminesafford both corresponding sulfoxides, substitution products, and the hemithioacetals, Pummerer type rearrangement products, upon treatment with sodium hydroxide in alcohol as shown in eq 24 (43)
b
I NTs
benzene
N-tosylsulf ilimines
-C=CHR4
I
R’
R’
RZ
Ph Ph Ph
Et n-Pr i-Pr
Ph Ph Ph
-0
Ph
ph -(CHzhPh -CH(Me)Ph
21
22
The formation of the thiohemiacetal (22) and the facile base-catalyzed H/D exchange of a-hydrogen suggest that the reaction involves an intermediate (23) (eq 25).
I
Ph-S-CH-CHpR
I NTs
hTS MeOH
-NTs
-CH=CH, -CH=CHMe -C(Me)=CH,
a
-(CH,),-CH=CHPh -C(Ph)=CH,
(%)
(27) (60) (80) (83) (50) (76)
One modification of this reaction may be found in the synthesis of vinylic sulfides by treatment of N-p-tosylalkylphenylsulfilimines, such as (24) with t-BuOK in benzene as shown by eq 26 (44). A few selected data are summarized in Table VI. R’
23
R3
(24)
S-CH2-OMe
ATS
vinyl sulfides
2
t-WOK
7‘
Ph-S-CH=CHR2
t TsNHz
25 24
(26)
2.6. Oxiranes in the Reaction between Sulfilimines and Carbonyl Compounds. N-p-Tosylalkylphenylsulfilimines readily give the corresponding reactive acarbanion (26) upon treatment with either alkyllithium or
266
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20,No. 2, 1981
Table VII. Preparation of Oxiranes Ph-S-CH-R
t Carbonyl Compounds
lbl
Table VIII. Preparation of Sulfoximines
-
\s R
I /
fNTS
\o
NTs
sulfilimine (R) H H H
oxirane,
Na Na
Ph
Li
Ph
Li
-
Ph
Li
M Li
carbonvl comDd PhCHO PhCHO PhCOCH,
%
100 56 60
o
88
c
71
PhCH=CHCOPh
71
e
0
NaH. The resulting a-carbanion (26), also reacts very readily with aldehydes or ketones, eventually affording the corresponding epoxides as revealed by eq 27 (17b, 45) R
Ph-S-CH-M
I
I
R'
f
\C=O
-
R
R'
method
yield, %
Ph Ph Ph Ph Ph Ph CH, Et CH, Ph
CH, Et i-Pr c-C.H. c-C;H;, PhCH, CH Et CH, Ph
a a
98 88 80 44 65 29 78 88 88 91
NH
R-S-R'
26 (27)
R
R2
CHC13
R-S-R'
t
(28)
1
0
28
-
KMn04
Ar-$-Ar'
I
Ar-S-Ar'
\ NH
NH
27
and a few representative data are tabulated in Table VII. A similar epoxide-formingreaction has been known well with a-carbanions of sulfoxides and sulfoximinyl ylides, which sometimes afford cyclopropane derivatives besides epoxides upon reaction with a-carbonyl compounds, except chalcone, which affords only the epoxide. The formation of oxiranes from carbonyl compounds with the sulfilimine is a kinetically controlled reaction and a convenient process for oxirane synthesis because of the facile work-up procedure and the readily available N-p-tosylsulfilimines. 2.7. Sulfoximines by Oxidation. Sulfoximines, nitrogen analogues of sulfones, are much more stable than sulfilimines, nitrogen isoelectronomers of sulfoxides, and have received wider industrial applications than corresponding sulfilimines. Many are used as medicinals, surfactants, lubricant additives, etc. However, most sulfoximines have been prepared by the following somewhat risky reaction using toxic and explosive hydrazoic acid, shown by eq 28 (46). Therefore, this procedure may not be applied for a large-scale preparation but is limited only to the lab-scale preparation of sulfoximines. Another simple method involves the reaction between sulfoxides and p-tosylhydrazide in the presence of Cu catalyst; however, the yield is generally quite poor while the reaction proceeds very sluggishly with aryl sulfoxides. Diary1 sulfoximines are, however, readily prepared in a large scale by oxidation of N-unsubstituted diaryl sulfilimines with KMnO, (24a,b). The yield usually increases in the presence of MgS04 (47). One perplexity in this oxidation is the removal of mangahese dioxide formed during the reaction. This difficulty can be avoided by our new procedure of oxidation of N-unsubstituted diarylsulfilimines with halogenating agents and subsequent treatment with alkali hydroxide. Unsubstituted sulfilimines were found to be oxidized directly by a dilute alkaline solution of NaOCl to corresponding sulfoximines quantitatively (48).Thus, for the first time, any sulfoximine can be produced in a industrial scale without any
H2S04
0
ijTs t PhSFjs
t HN3
I
t
-
I
R2/
NTs
a a a a b b
risk, such as health hazards, disposals of toxic waste, etc. The method is shown in eq 29.
T O -
[Ph-S-CH-C
a a
dil. NaOH
Ar-S-Ar' I
4
NH
t
\
NX
X = CI. Br.
I
29
Like other trivalent organosulfur compounds, such as sulfoxides, N-p-tosylsulfilimines are oxidized by such nucleophilic oxidants as H202/NaOHor mCPBA/K2C03(49) to the corresponding N-p-tosylsulfoximines in excellent yields according to the eq 30, as the data listed in Table VI11 indicate. By this method N-p-tosyl-S-benzylsulfoximines, hitherto unavailable by other procedures, can now be prepared readily. 0 (0)
R-S-R'
i Ts N
t
H2OZ/NoOH or
-
(b) mCPBA/KZC03-H20
EIOH
R-S-R'
t
conc H2SO4
*
I NTs
30
R-S-R'
P 1 NH
(30)
2.8. Aziridines by Treatment of Electrophilic Olefins with N-Unsubstituted Diarylsulfilimines. N-Unsubstituted sulfilimines, being rather strong bases (pK, = 8.2) as alkylamines, are good nucleophiles and undergo the Michael addition to various electrophilic olefins such as a,P-unsaturated ketones or esters to afford aziridines often along the enaminoketones, but not the simple Michael addition products. An example with dibenzoylethylene is shown in eq 31 (50)
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 2, 1981 267
of PhcoxH - Hv:oph +. Table IX. Preparation
PhCO
t
PhpS-NH
H
Aziridines
COPh
32 PhCO
PhpS
-
NH2 x,"OPh NH
yield, %
-
t O :-P 'hH
olefin
(1)
(2)
(3)
50
50
100
UCCPh 43
55
100
46
23
91
40
26
64
CCPh PhCO
By this reaction, N-unsubstituted a-ketoaziridines, obtainable only through multiple steps in the past, can be prepared in one step. Simple Michael additions also take place with some electrophilic olefins such as acrylonitrile and phenylvinyl sulfone without forming any aziridine derivative as depicted by eq 32. This, however, is an interesting way of preparing N-alkylsulfilimines (51). Addition of N-unsubstituted diphenylsulfilimine to an acetylenic triple bond leads to the'formation of a new heterocycles (25),such as 35 via the initial Michael addition as shown in (eq 32). Some of these results are collected in Table IX. CHZ=C"CN
/ PhpSNH
Ph 2.5
-------
-
Ph2S-
CHECCOPh
33
-
NCH=CHCOPh
N-0
I
II
,C-Ph
CH C ' H'
(32)
35
N-Alkylsulfilimines, e.g., the N-benzyl derivatives, can also undergo an analogous reaction, affording a mixture of the corresponding aziridines and enaminoketones, like the N-unsubstituted sulfilimines (eq 33) (52).
-
H xrOph
MeOOC
P h \ 7
67
89
CCPh
H,C=CHCN
Ph,S+NCH,CH,CN (69)
Ph,SNH t RCHO
34
PhpSNCH2Ph f
CWMe
-
Table X. Preparation of Nitriles
NCHpC H 2 CN
P hCO
Memc\
PhCO b C O P h
I I
'
CH2Ph PhCH2NHx:OPh
(33)
PhCO
2.9. Nitriles by Treatment of Aldehydes with NUnsubstituted Sulfilimines. Despite the highly nucleophilic character, N-unsubstituted sulfilimines do not react with ketones or aldehydes at room temperature; however, they do react with aldehydes in refluxing benzene to afford the corresponding nitriles in excellent yields (53). The reaction with ketones in refluxing benzene does not give any nitrile but is complicated and affords a complex mixture when the reaction was performed at a higher temperature ca. 80 "C. The conversion of aldehyde to nitrile is so simple a reaction that it will attract wide attention in organic syntheses. The reaction can be applied for all kinds of aldehydes, including such an aldehyde as cinnamaldehyde, which gives cinnamonitrile in good yield, as the data in Table X reveal. The overall reaction may be shown by eq 34. Ph2S-NH + RCHO RCN + PhzS + HzO (34)
-
2.10. Syntheses and Applications of Optically Active Sulfilimines. Sulfiiines, having a stable pyramidal
aldehydes C,H,CHO p-CH,C,H,CHO n-ClC.H.CH0 ~-cH~O~,H,CHO p-HOC,H,CHO CH,(CH,),CHO CH,(CH,),CHO trans-PhCH=CHCHO p-HOCC,H,CHO
RCN
+ Ph,S nitriles, % 65.8 92.7 89 83.6 90 91 88 88 78
structure, can possess optical activities, if two substituents are not identical. In fact, an optically active sulfilimine was first resolved by Phillip and Kenyon more than half a century ago ( 7 ~ ) .Asymmetric synthesis of optically active sulfilimines, however, was developed only recently by Cram et al. (7b) and Kajer and his workers, who obtained optically pure N-p-tosylsulfilimines through treatment of optically pure sulfoxides with either TsNSNTs or TsNSO. In order to apply this reaction, one has to use an optically active sulfoxide which is sometimes hard to obtain, while neither TsNSTs nor TsNSO is easy to handle. Nevertheless, the reaction, shown by eq 35, is clean and useful in the lab-scale preparation. TsN
23
p
-SNTs
P-T
-61
-61
p
(-)-(S)-
(+ )-(R)-
A more convenient method, applicable in large-scale preparation developed by us, involves asymmetric induc-
268
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20,No. 2, 1981 GMe
OM?
OMe
GCH3
/
'dCOCH,C^H O 'H
I I
CH3
I
hv
t
hv or HCI
*
tion in one pot reaction. o-Methoxyphenyl or a tolylphenyl sulfide is mixed with tert-BuOC1 together with 1-menthol to afford the ccirresponding asyrdmetrically induced 1menthyloxysulfonium salt which is then treated with TsNH-Na+, eventually affording the optically active N tosylsulfiliqine of 15-30% optical purity in ca. 60% chemical yield according to the path shown by eq 36 (54). Some of these data are listed in Table XI.
&s-R
t f-BuOCI X
I-menthol
X
Table XI. Preparation of Optically Active Sulfilimines o-CH,GC,H,-S-C,H,
i
NX
iff ID
X p-CH,C,H,SO, p-ClC,H,SO, p-CH,C,H,SO, C6H5S02
C,H,CO o-CH,C,H,SC,H,
.1
-31.9 (-98) -28.3 -19.5 - 20 -13 -15.5 (-41)
"P!. yield, purity, %
%
62 60 20 62 65 48
32.6
_-. _-.
37.8
NTs I
0-Ment
36 X = Me, OMe; R = Ph, etc.
One advantage of this asymmetric synthesis is that the sulfilimines (R = Ph, X = CH,, OCH,) thus formed can be made 100% optically pure just by one recrystallization (50),while the optically pure sulfilimine can also be obtained by seeding a tiny piece of the optically pure crystals into a Paturated solution of the racemic sulfilimine. Since the racemic sulfilimines can be prepared so readily on a large scale, this is a very efficient way of preparing large amounts of optically pure N-p-tosyl-o-substituted diarylsulfilimines, which may be used for organic syntheses of asymmetrically induced products subsequently. The N-p-tosylsulfilimines thus formed can be detosylated to the N-unsubstituted sulfilimines for further uses in organic syntheses of various optically active organosulfur compounds and desired asymmetrically induced products. One such example is the one-step synthesis of optically
active aziridines by treatment of a,P-unsaturated ketones with this optically active sulfilirdinas, as illustrated by eq 37. In this reaction the product, aziridine, showed ca.30% optical induction while the chemical yield was excellent (50-100%). Thus, the reaction has been shown to be an excellent method for the synthesis of optically active aketoaziridines. Some of these data are listed in Table XII. Other asymmetrically induced reactions with the optically active sulfilimines may be found in the acylation and subsequent hydrolysis to form optically active amines, photolysis and pyrolysis yielding optically active heterocycles etc., which are also illustrdted in eq 37 (where the asterisk denote optically active centers). 3. Utilizations of Sulfilinifnes Despite the growing demand of sulfilimines in various organic syntheses, utilization of sulfiliines themselves has not been fully explored yet. However, since most sulfilimines are stable and yet possess a reactive S-N linkage into which various substituents can be introduced, many derivatives have been and will be prepared for practical uses.
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 2, 1981 269
in a wide variety and shown to be useful as herbicides in field tests (60). Prosulfalin is the commercial name for some of the derivatives.
Table XII. Preparation of Optically Active Aziridines
NH
R PhCO Ph Ph Ph Ph Ph
aziridines,
R’ Ph Ph p-CH,OC,H, p-CH3C6H4
p -Br C,H, =(COOCH,),
%
laln
OP!. DUKltY
61 96 33.2 50 83 42
-20.0 -99.0 -89.5 -103.5 -97.7 -22.0
------43.0 ---
42
32.6
R = Pr, Bu; R = Pr, Et; RZ = Me, Et, Pr; R3 = Me,Et, Pr, Ph; R’ = R 3 = (CH,),, (CH,),O(CH,),, (CH,),, (CH,),; R2 =’ Me, Et, Pr; R3 = Me, Et, Pr, Ph
One such example is the antimicrobial activity of N-ptosylsulfilimines, which have a skeletal structure similar to those of sulfamic acids. Tarbell et al. synthesized in 1943 various N-sulfonylsulfilimines (38) according to the reaction shown in eq 38, expecting that those sulfilimines AcNHC6H4SOZNCl.K + RR’S R, R’ = Me, Bu, Et, Pr, Ph, To1 RR’S N S O ~ C ~ H ~ N H(38) AC
-
38
which possess a p-acetoaminosulfonylamide group will have good potentials to be used as “sulfur drugs” which also bear the p-aminosulfonylamide (PAS) group. However, among many tested, only the methyl p-tolyl derivative was found to be slightly effective against streptococcus hemlyticus, but the effect was negligible as compared to PAS (55). Sulfilimines (39) which possess either sulfinyl or sulfonyl vinyl group on the central sulfur atom have been tested widely as anti-microbial agents (56). Likewise, 645nitro-l-methyl-2-imidazolyl)-6-amino-Striazolo- [4,3-b]pyridazines (40) are also shown to be potential antimicrobial agents (57). A similar effect was reported with nitrofurane derivatives of sulfilimines (41) (58). CIS
o r trans R2C6H4S02N-S-CH=CHSOnR
39 R, R = Ph, Tol, PhCH,, p-CIC,H,,p-FC,H,, p-MeOC,H,, R’ = CH, etc.)
R
40
R = N = SMe,; N = S(O)Me,; N = CHNHCH,CH,OH; N = CHNMeCH,CH,OH etc.
,-(&
(cH
=cH),,c(N =c NH, ,
ioaN*y
xso2
so2
R = C1, Ph,S=NCOX (44);-k= Me,SN, [(4-CF3C,H,),S=NCOX, X = CH,NHMe, CH,CH,NMe,]
-
Sulfilimines of S-mustard gas, (C1CH2CH&3 NS02R, were reported to have tumor-inhibited activities unlike the corresponding sulfoxides or sulfones (63). Meanwhile, N-fluorosulfilimines are used as catalysts for polymerizations of ethylenic compounds and fluoroolefins, though the mechanism of the catalytic action is not known at all (64,65). Sulfilimines of such structure, RSOzN SR’R”, are claimed to be antioxidants of polyolefin by the addition of the sulfilimine at 0.02-0.05% (66). Similar sulfilimines can be used together with vulcanization accelerators as scorch inhibitors for vulcanized rubber (67).
-
Literature Cited (1) For summarized references of organosuifur compounds, see ReM, D.
I R‘
( n = 1 or 2;
Although none of sulfilimines has been sold as medicinals, sulfilimine (43) is known to have dimetic and hypotensive actions (61),while N-acyl-S,S-diphenyhulfilimine (44) may be used as an antidepressant or as a central nerve system stimulant in the future (62).
=x
yo2
41 I, X = SMe,; 11, X = H,
S,S-Dimethyl-N-carboxyl or arenesulfonylsulfilimines have some fungicidal activities and the effect was shown to increase by changing methyl group to alkyl groups of longer chains, while the bactericidal activity seemed to depend on the medium used (59). Sulfilimines in which the N-sulfonyl group is attached to 3,5-dinitrosubstituted phenyl group (42) are prepared
H., Ed. “Organic Compounds of Sulfur, Selenium, and Tellurium”, Voi. 1-5,The Chemical Society, Burlington House: London, 1971-1979. (2) Reviews on sulfilimines: (a) Field, L. Synthesis 1972, 101. (b) Roesky, H. W. “Sulfur in Organic and Inorganic Chemistry”, Vol. I, Senning, A,, Ed.; Marcel Dekker; New York, 1971; p 13. (c) Gllchrist, T. L.; Moody, C. J. Chem. Rev. 1977, 77, 409. (d) Oae, S. “Organic Chemistry of Sulfur”, Plenum: New York, 1977;p 388. (e) Kucsman, A.; Kapovitz, I. Phosphorus Sulfur 1977, 3, 9. (f) Johnson, A. W. “Organic Compounds of Sulfur, Selenium, and Tellurium”, Voi. 1, 1970,p 299; Vol. 2, 1973;p 322; Vol. 3, 1975,p 363;Haake, M.. ibM., Voi. 4, 1977,p 105;Vol. 5, 1979,p 97;Oae, S.; Furukawa, N. ibid.. Voi. 6. 1981.in Dress. Nicoiet, B. H.; Willard,71. D. science 1921, 53, 217. Mann, F. G.; Pope, W. J. J. Chem. Soc.1922, 727, 1052. (a) K B l d n , A. Acta Crystai/ogr. 19S7, 22, 501. (b) Mazey, P.; Kucsman, A. J. Chem. Soc., Faraday Trans. 2 , 1972, 68, 2060. (a) G x t z , H.; Schmldt. J. Tetrahedron Lett. 1971, 2089. (b) Cleus, P.; Vycudillk, W. Monetsh. Chem. 1970, 701, 405. (a) Clark, S. 0.; Kenyon, J.; Phillips, H. J. Chem. SOC.1927, 188. (b) Yamagishi, F. G.; Rayner, D. R.; Zwickner, E. T.; Cram, D. J. J. Am. Chem. Soc. 1973, 95, 1916,1925. (c) Christensen, B. W.; KJaer, A. Chem. Commun. ISSO, 934. (d) Morlyama, M.; Yoshimwa, T.; Furukawa, N., Numata, T., Oae, S. Tetrahedron 1978, 32, 3003. (a) Furukawa, N.; Harada, K.; Tsujihara, K.; Oae, S. Tetrahedron Left. 1972, 1377. (b) Menon, B. C.; Darwlsh, D. Tetrahedron Lett. 1973,
4119.
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 2, 1981
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Received f o r review September 24, 1980 Accepted December 15, 1980
