373
J . Org. Chem., Vol. 43, No. 2,1978
Communicatioiis
Preparation of Cyclopropanes from a,P-Unsaturated Aldehydes, Esters, and Ketones
Table I . Cyclopropyl Sulfones from 0,P-Unsaturated Carbonyl Compounds Sul-
Summary: cu,P-Unsaturated carbonyl compounds are effi-
fone tosylate,=
ciently transformed into the corresponding cyclopropanes by a sulfone-mediated bond formation.
Cyclopropyl sulfone (% yield)
%
Sir: In connection with natural product synthesis, we have
Carbonyl compd
yield
been concerned with the problem of converting a,p-unsaturated compounds into cyclopropanes (eq 1)and recently de-
Rr
0
veloped a method to accomplish this; however, the open chain hydrocarbon was also formed (eq 2).l We now report another
I
R'
II 0
3 . CH,SO,Cl/Pyr 5. L i / N H , 5
R* (2) R approach which cleanly gives the desired goal. The new strategy is summarized in eq 3. It was hoped that
-RyR' 1. C.H.SH C,H,SH 2. L:A
