[1-(Phenylthio)-2-carbamoylallyl]lithium reagents. Electrophilic substitution and formal anionic 3 + 2 cyclization-elimination

Article abstract of DOI:10.1021/jo00378a011

The formation and reaction of a number of [1-(phenylthio)-2-carbamoylallyl]lithium reagents is reported. Lithiation of the β′- and β-(phenylthio)-α,β-unsaturated carbamates provides 8, 13, and 35 from tertiary amides and 26, 32, and 45 from secondary amides. These reagents are geometrically stable and react regioselectively with a variety of electrophiles. The reaction of 8 with N-methyl-N-phenylacrylamide gives the cyclopentenes 42 and 43 while reactions of 13 and 45 with azobenzene gives the dihydropyrazoles 44 and 46, respectively. These sequences involve β′-directed lithiations, stepwise anionic 3 + 2 cyclizations, and thermodynamically driven eliminations. The formation of the quinoline 47 from 12, an adduct of 8 and azobenzene, is reported.