11 Phosphonates Containing Sulfur and Selenium: Synthesis, Reactions, and New Applications M . MIKOŁAJCZYK, S. GRZEJSZCZAK, W. M I D U R A , M . P O P I E L A R C Z Y K , and J. OMELAŃCZUK
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Center of Molecular and Macromolecular Studies, Polish Academy of Sciences, Depart ment of Organic Sulfur Compounds, 90-362 Łódź, Boczna 5, Poland
The ambident behaviour of sulfur in terms of its ability to stabi1ize adjacent negative and positive charge at carbon has made this element a focal point for new reagents and reactions (1). For this reason our concern has focused on the synthesis of new phosphonates containing sulfur and selenium and the exploration of their application in synthetic and stereochemical studies. It was found (2,3) that the best synthetic approach to phosphonates containing sulfur and selenium in the α-position is ba sed on the reaction of elemental sulfur and selenium with a-phosphonate carbanions. It is interesting to note that, in contrast to sulfur, selenium may be added in this way to the tertiary car bon atom.
In an extension of this work a new route to unsaturated six -membered sulfur heterocycles 1 has been investigated which consists in the internal Horner-Wittig reaction of the appropriate α phosphoryl sulfoxides or sulfones 2 prepared as shown in Scheme I. Thus, the sodium salts of α-phosphoryl thiols 3 |R=H (a) R=Me (b)| were reacted with ethylene ketal of 5-chloro-pentanone-2 in ethanol solution under ref1ux to give the corresponding condensa tion products 4 in high yields (80-90%). Their oxidation followed by deblocking of the carbonyl group afforded sulfoxides 2,a,b and sulfones 2,c,d which on treatment with n-butyllithium were conver ted into the desired unsaturated thian-S-oxides or S-dioxides 1. 0097-6156/81/0171-0055$05.00/0 © 1981 American Chemical Society In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
56
PHOSPHORUS CHEMISTRY
Scheme I
1.NaOEt/EtOH 1.[0]
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ι >^\SH
0 0 2 . C l \ x v X •
„ Γ r E t O ^ P ^ ^ S ^ \ / \ ^
+
2.HJ) L
(EtO) P9
a» R=H,
n=l
b,
R=Me, n=1
c,
R=H, n=2
d,
R=Me, n=2
The next part o f the present study concerns the o x i d a t i o n o f the phosphonate and thiophosphonate carbanions. G e n e r a l l y , t h i s react ion was found to occur in two di rect ions depending on the s t r u c t u r e of the s t a r t i n g phosphonate and the reaction condi t ions. The l i t h i u m s a l t s o f thiophosphonate carbanions 5 give on t r e a t ment wi th oxygen the corresponding α - h y d r o x y t h i ô p h o s p h o n a t e s 6, exc1 us i v e l y .
1.0 ,-78° 2
R'
2.H.0* (R0) PCHLi
2
o
2
^
(R0) P-CH-0H o
2
II
II
s
s
I
I Yield
(%)
6
3 1 p
a,
R=Me,
R'=H
58
91.2
b,
R=Me,
R'=Me
55
99.8
ç,
R=Et,
R'=Me
67
96.3
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
11.
MiKOLAJCZYK E T A L .
Phosphonates
Containing
S and
57
Se
As expected, the reaction o f the l i t h i u m s a l t s of phosphonates 2 with oxygen r e s u l t s in the format ion o f di a l k y l phosphori c aci ds 8 and carbonyl products i . e . the cleavage o f the C-P bond takes pi ace (4,5). Howeve r , when the halomagnes i urn s a l t s o f phosphona tes 7 were o x i d i z e d , a-hydroxyphosphonates 2. were formed. Scheme I I R 0 ,-78° — + R - Ph 2
(EtO) PCHLi 0
2
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II
ο
(Et0) P0H + RCH | I 0 0 o
2
8
Ζ
O ,-78
R=H,Me
c
(EtO) P(0)CH(R)OH 9
0
(EtO)«PCHMgBr 9 + 8 + PhCHO
R=Ph
The bi di r e c t i o n a l course of the oxi dation may be r a t i o n a l i • zed by assuming that the peroxi de i ntermedi ate A formed in the f i r s t reaction step undergoes the intramolecular decomposi t i o n and/or intermolecular reaction as shown in Scheme I I I . Scheme I 11 X"
Li
+
SCO
I >P — CH-R
I
—
I
ο— ο H
II
I
X
Li — 0 A
+
>P(X)0H + RCHO
8
>P — CH — 0
2 >PCH0Li X=0,S H >P(X)CH(R)0H
6(a)
With rega rd to the phosphorus stereochemi s t r y , a new stereospeci fi c synthesi s o f chi ral 0 , 0 - d i a l k y l thiophosphori c acids (6,J7) has been developed whi ch i s based on the Horner-Wi t t ig rea ct i on of the opt i c a l l y a c t i ve phosphonothionate carbanions con tai ni ng the s u l f o x i de o r di t h i o a c e t a l m o i e t i e s . The transformation of (R)-(+) 0-methyl 0 - i s o p r o p y l methanephosphonothionate (10)(8) into (R)-(-) 0 - i s o p r o p y l phosphorothioi c aci d (1J.) best i l l u s t r â t e s thi s method.
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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58
PHOSPHORUS
(î) n-BuLi , (-)TolS(0)0Men ; ( i i ) n-BuLi , (PhS)~; PhCHO
CHEMISTRY
( M i ) n-BuLi ,
In a s i m i l a r way t h e a b s o l u t e c o n f i g u r a t i o n R a t p h o s p h o r u s was a s s i gned t o (-) 0 - e t h y 1 0 - i sop ropy1 phospho rothioî c a c i d (1_4) , ( - ) 0 - j v - b u t y l 0 - i s o p r o p y l phosphorothioî c a c i d (V5) and (+) 0-methy1 0 - n a p h t h y 1 p h o s p h o r o t h i o i c a c i d ( 1 6 ) . The c o r r e c t n e s s o f t h e c o n f i g u r a t i o n a l a s s i gnments was c h e c k e c F b y X - r a y a n a l y s i s o f ( + ) - S - m e t h y l 0-methy1 O - n a p h t h y l p h o s p h o r o t h i o l a t e ( 1 J ) by means o f t h e B i j voe t method.
Literature Cited 1. Block, Ε. "Reactions of Organosufur Compounds"; Academic Ρress New York, 1978. 2. Mikołajczyk, M . ; Grzejszczak, S.; Chefczyńska, A. and Zatorski, A. J.Org.Chem. 1979, 44, 2967. 3. Mikołajczyk, M . ; Grzejszczak, S . ; and Korbacz, K. Tetrahedron Letters in press. 4. Davidson,A.H. and Warren,S. J.Chem.Soc.Chem.Commun.1975, 148. 5. Ζimmer, H.; Koenigkramer, R.E.; Cepulic,R.L.; and Nene, D. M. J.Org.Chem.,1980,45,2018.
6. Mikołajczyk,M.and Leitloff,M. Russ.Chem.Rev. 1975,44,670. 7. Hall, C.R.; Inch,T.D. J.Chem.Soc.Perkiη I, 1978, 1104. 8. Mikołajczyk, M.; Omelańczuk, J.; Para M. Tetrahedron, 1972, 3855. RECEIVED
June 30, 1981. In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
