An unexpected side reaction in the transformation of an alcohol to an amine facilitated by triflic anhydride-pyridine

Two N-triflyl-4-vinyl-1,4-dihydropyridines 3 and 4 were identified as isomeric impurities in the mother liquor of a 3-step "telescopic" transformation of a secondary alcohol 1 to an amine 2 facilitated by triflic anhydridepyridine. The vinyl ether moiety of impurities 3 and 4 was readily hydrolyzed under acidic condition to form a keto-alcohol product 5 where four chiral centers were established on a cyclopentane ring. Another keto-alcohol impurity 6 was also isolated from the same mother liquor and identified as a hydrolysis product of the putative vinyl ether intermediate V in support of postulating a plausible mechanism for such an unexpected side reaction. The unexpected finding of the vinyl ether intermediate V could be derivatized with electrophiles besides Ntriflylpyridinium to form a variety of compounds with four chiral centers established on a cyclopentane ring.