Preparation of an intermediate for N-(methylsulfonyl)-1,2,8,8a-cyclopropa[c][1,2-b:-4,3-b']dipyrol-4(5H)-one

Claim 1

A process for preparing a compound of the formula wherein R 2 and R 3 are H, alkyl of from 1 to 5 carbon atoms, inclusive, and phenyl; R 4 is selected from the group consisting of SO 2 R 2 , SO 2 CH 2 CO phenyl, CO 2 CH 2 Z where Z is selected from the group consisting of CH 2 I, CCl 3 , CH 2 SO 2 R 2 , Ph(phenyl), and fluorenylmethyl, and X is selected from the group consisting of OSO 2 R 2 , Cl, Br, and I, which comprises reacting a compound of the formula ##STR4## wherein R 2 , R 3 , and R 4 are as defined above, with a reagent selected from the group consisting of sulfonyl chloride, carbon tetrachloride/triphenylphosphine, carbon tetrabromide/triphenylphosphine, and N-iodosuccinimide triphenylphosphine, separating the organic phase from the reaction mixture, drying and concentrating said organic phase, and recovering the desired product by silica gel chromatography.