Methyl sulfinates as electrophiles in Friedel-Crafts reactions. Synthesis of aryl sulfoxides.

The Friedel-Crafts reaction of methyl alkyl- and arylsulfinates with aromatic systems, activated by one or more electron-donating substituents (OH, OMe, NHR, NR(2)), provides alkyl aryl and diaryl sulfoxides under mild conditions and in moderate to good yields. The very high regioselectivity usually observed in these sulfinylation reactions is rationalized on the basis of a Wheland intermediate having a trigonal bypyramidal structure in which steric and electronic interactions are significant factors strongly destabilizing the attack to the ortho positions.

Introduction of a substituent at the 5"-position of N-Boc neomycin B under Mitsunobu reaction conditions.

Because of the peculiar reactivity of the idose part of N-Boc neomycin B , special care must be exercised to introduce a substituent at the 5"-position of the antibiotic when using Mitsunobu reaction conditions.