Imidazolylphosphonamidochloridothionat es
1;
I
\
I ~ = l l \ d l o L ' ~ l l ~ \Rl = f 1 11. 1 ( I K = H oi b,t
0 1
1.h
Sirice compounds 11 represented a iiovel class of compound coritairiirig two furidameritnlly diff e m i t leaving groups, C1 m d imidazole, a t the central P atom, we studied the hiologicnl :ii1 ~ 1 2i.s 1 t hc chemical asperti of the new conipoundi. Biological Aspects.--C'oiiipoiiitdb of ytriirt t i r ~ I1 \\ere inveqtignted aq to thcir fungicidal artivity againit poi\ dery milden :tnd h t c hlight (T:ihl(> I). The fungicidal data liyted \\ erc minimiim concentrntion_i (11 racrmic I and I1 in pm t - pc'r riiilliiiii O ~ : ~ C ~ L I ~ OformiiltiUtioii rrquircd to producc com1)l(~t(~ rotit r i l of the t u o pl:tiit clihc'iv- rnriitiot~c(l
IXIDAZOLYLPHOSPHOSA~IIDOCHLORIDOTHIOSATES
September 1969
products was completely suppressed if the alkyl groups nt the amido IZ' were a t least as bulky as i-Pr. Thc same observations mere made if distilled I1 was redistilled. These findings clearly indicated that compounds I1 underwent the following disproportionation reaction (a) and t h a t the extent of occurrence of this reartion was controlled by the size :md sh:ipc of the groups in place of alkyl nntl lt.5
S
795 R
C1
-
VI
-
I
l k
R I
N-P(S)-N
A 0 W
GCH I-
N(C$-,)? VI11
I\'
The noteworthy feature of observation was not so much the fact that a disproportionation reaction occurred in the first place but that this reaction took place already a t 80-100". Thermal disproportionations of thionophosphoryl chlorides containing asymmetric P are a well-known phenomenon but usually require temperatures of about 13O0.'j Possibly, the new reaction (a) could involve the initial formation of C1- and imidazolyl, leading to a redistribution of these groups a t P. I n a more attractive alternative the initial step could be a n attack of the rather strongly nucleophilic azole S of one molecule of I1 on a somewhat electrophilic P atom of another molecule of 11, leading t o the liberation of C1- and subsequent formation of I11 and IV. I n order to test this hypothesis we studied the nucleophilicity of I1 toward C in IIeI. Using I I b and its ?-Et homolog (IIg) as representative nucleophilic reagents we found that I I g snioothly produced the expected derivative of structure VI (1%= E t ) in near qutntitative yield. The nmr spectrum of the reaction product clearly revealed that it mas thc azole S and not the S in IIg which had been methylated.' An analogous reaction of I I b with I I e I did not provide the expected homolog of structure TrI (R = H). The main product actually isolated from this reaction was found to have struct u r e V I I (€3 = H). A t first sight it might appear uriusual that two homologous species of I1 should behave so differently in their reaction with I I e I . However, the unexpected formation of TI1 (It = H) could have occurred in the following manner. If the electron deficiency of I' in T'I (R = H) is similzir to the electron deficiency of C in Me1 the nucleophilic I I b will react not only with -\IeI but also with VI (R = H). Reaction with the latter would produce I11 (alkyl = E t ) and the novel structure VI11 (R ( 5 ) T h e yields given in Tables I1 for I11 are d a t a of recovery and not of formation since the high vacuum applied prevented complete recovery of 111 a x formed. (6) L. C. D. Groenweghe, L. Alayer, and H. E. Ulmer, Abstracts, 139th Piational Meeting of t h e American Chemical Society, St. Louis, No., illarch 1'361. p M-18. (7) Cf. ref 2b.
= H). This compound will react with RIeI to afford the new structure VI1 (R = H). We proved the existence of VIIIa (R = H ) and T'IIIb (R = E t ) by methylating IVb (alkyl = ethyl, R = H) and IVg (alkyl = E t , It = E t ) under mild conditions. Thus, the over-all reaction of compounds of the novel structure I1 with excess Ale1
I1
+&le1
+I1
TI ----f \?I1
+Me1 __f
-111
VI1
(b)
may proceed as shown if alkyl is ethyl. This sequence of reactions apparently is arrested a t stage VI if R is E t but proceeds to stage VI1 if R is H. We interpret this phenomenon by assuming that the nucleophilic attack of I1 on VI1 is sterically affected by the size and shape of K,unless this substituent is H. The same interpretation can serve to explain the results of reaction a. An ionic dissociation-recombination mechanism may be conceivable for reaction a but mould be of no help in regard to the reaction involved in b. The discovery of the reaction I1 Ale1 4 VI suggested that racemic I1 might be resolved by treating it with the I r e ester of an optically active acid, e . g . , a-tlcamphorsulfonic acid. This novel method of resolving asymmetric organophosphoramides was developed i i i our laboratory for compounds of structure I (X = P h , R = Me, alkyl = Et).2b I t did not prove successful in the case of 11. The diastereomeric complex was found t o degrade too rapidly to permit resolution.
+
Experimental Section* For ir analyses, a Beckman IR-9 filter-grating spectrometei, over the 3 8 0 0 - 4 0 0 - ~ m -region ~ was employed. Spectra of 107) solution of the compounds in CCl, (for the 3800-1333-cm-' region) and in CSZ(for the 1333-400-cm-l region) were scanned using 0.1-mm KBr cells. For nmr analyses, a Varian rl-60 instrument and 20% solutions of compounds in CDCla were used. The characteristic ir frequencies (cm-') and chemical shifts relative to TMS for the imidaxol-1-yl protons used for identification purposes have been reported previously.* The melting points are uncorrected and have been determined according to Be~-henke.~ N,N-Dialkyl imidazol-1-ylphosphonamidochloridothionates(I1) were prepared by the dropwise addition of a solution of imidazole (0.5 mole) and EtgN (0.55 mole) in 1,2-dimethoxyethane (-200 ml) to a n agitat,ed solution of the appropriate ?;,X-di,zlkyl ( 8 ) Where analyses are indicated only by symbols of the elements, analytical results obtained for these elements were within 10.4% of the theoretical values. (9) I.. F. Rerhenke, A n d . Chem., 33, 65 (1961).
C: c:alcd, 28.63; foiind, 99.20. C1: calcd, 13.30; foiind, 12.80. 'I
( J : calcd, 83.80; foiind, :Z.i.:iX. (.'I: calcd, 14.40; foiiiid! 1:3.90.
I)hosphoramidodichloridothioriste (0.5 inole) in the sanie tliliieiit 1-200 ml) a t 0-5' over a 1-4-hr period. The resulting mixtiii,cx was stirred a t 0-5' for -18.0 hr and diluted with 250 nil r i f 1,2-dimethoxyethane, the iriso1iil)lc lCt3STI-C- w:i\ filterctl. and the diluent was removed f r o m t h r filtrate by evaporatioii. The residue was tskeii iip iti CCli ( 2 5 0 ml), the iiimliihle, were filtered, and the solvent w a s evaporaicd from the fi1tr:itcL. l'hr resulting residue was treated iii a >iInilar niaiiner with hexane. The crudes thus obtained represented the following compuiintl.: (yields iii per cent of theory given i i i parenthesesj: I I a (00.4'1, 1% (84.0), IIc (88.2), IId (60.5), and I I e (quantitative). Iii t h e preparation of IId the reaction mistiire had t o be refluxed flJr 18.0 hr to ensure :t good reactir~ii. ILtillatioii the crridr product gave a 5 3 . 3 5 yield: the di>till:itp ( ing (inp 46'). 3Iolecular dis1ill:itioti of ihc ot1ir.r criidr- i l f structure I1 gave prodiirt. of tii.i)riii)iirtioii:~ii~jii :r- >tio\vir i i i Table 11. Comhiistioii d:it:i of c.riidtb 1T:i e :iiid I J t i > ~ ~ i (&it d :I after distillatioil were f o r u i d to be :I> giveii iii Tahle 111. The 2-ethylirnidazol-1-y1 hOIll(JlOg$ \vrre prepared i i i m i a i i d ~ i gous manner. The niaiii alteratioir of the above p i ~ i ~ c c ~ dIV:I. ~ire reaction temperature. IIf aiid TIg n w e >yithe>izrcl a t room temperature, while 1111 i,eqriired reflining. Yield> I J f the c . i , i i r l ~ : react,ion products were a, follow: IIf (91 .Y1, IIg (\Jl.(i), a l i i 1 I I h (90.5). llistillation c ~ fthese c~t,iidr+gavr t h e p r o d i i c ~ sahowti i i i Table 11. llefli ] i i i v : ~ l r i i i riic~lar : i n i o u i i t , - rif 2 - e t I i ~ ~ l imidazole, S , S - d i i .1 1) t i ( i ~ ~ ) h o i i a r i i i tidichlcii,itli li ~t Iiic i i i a t r , and E t a s in 1,2-din ct1i:riic. f o i , 40.0 hi, pave :t 49.0c; !.icltl iif TIi (nip 124-126 I,2-tlitric.thr~xyelh:iiie). .hic:il h t : i after di~ti1lutii)iiw ~ v e:I, ti Table 111. The .-iri~i:liii~r of 1he-;e conipoiiiirL- \v:i? i i i with recently eat:iLli+d i r anti rinir staiiclardq.2 N-Dialkyl Diimidazol-1-ylphosphinamidothionates (IV 1.
