Toward the Synthesis of Biologically Important Chlorins, Isobacteriochlorins, and Corrins. Cyclic Enamides from Acetylenic Amides

Cyclic enamides 1 of a type useful in the synthesis of naturally occurring chlorins, isobacteriochlorins, and corrins have been prepared by a process involving 5- exo - dig cyclization of the appropriate acetylenic amides 11 . The desired cyclization is catalyzed by either n -Bu 4 NF or LiAl(NHBn) 4 .