3-Vinyl-substituted 3-pyrrolin-2-ones

This method for preparing 2-phenyl-1-pyrroline, and assorted 2-substituted 1-pyrrolines, is one of the best currently available, particularly because it reproducibly affords clean materials. Generally, the procedure is amenable to various aromatic esters 2 it has also been applied successfully to aliphatic esters (Table I).3 An advantage of this method is the use of readily available, inexpensive N-vinyl-pyrrolidin-2-one as a key starting material. This compound serves effectively as a 3-aminopropyl carbanion equivalent. The method illustrated in this procedure has been extended to include the synthesis of 2,3-disubstituted pyrrolines. Thus, alkylation of the enolate of the intermediate keto lactam, followed by hydrolysis, leads to various disubstituted pyrrolines in good yields (see Table II).3... 

Annelation of steroidal dienamines with substituted phenacyl bromides (7 examples) or with benzenediazonium salts (11 examples) has been shown to lead to the corresponding furano- and indolo-steroids.89 Thus the A3,5-dienamine derived from A4-androstene-3,17-dione reacted with p-bromophenacyl bromide to yield the A5-androstano[3,4-h]furan (199) in 26% yield, and reaction of the same A3,5-dienamine with benzenediazonium fluoroborate at -45 °C led to formation of the hydrazone (200) which underwent Fischer-indole cyclization on treatment with phosphorus oxychloride to produce the A4-androstano[6,7-6]indole (201). The A3,5-dienamine derived from 17/3-acetoxyandrost-4-en-3-one has been converted into the benz[4,5,6]-steroid (202 R1 = Me, R2 = H) by reaction with methyl vinyl ketone and into the analogous benzsteroid (202 R1 = H, R2 = Me) on treatment with crotonal-dehyde.90 A route to the condensed pyrroline ring system (203) has been devised... 

Clayden and coworkers reported intramolecular Michael-addition— fragmentation leading to 3-vinyl- and 3-aryl-substituted 3-pyrrolin-2-ones (20040L609). For example, treatment of the carboxamide 178 (DEB = 1,1-diethylbutylcarbonyl) with LDA gives 3-pyrrolin-2-one 180 through a fragmentation of the initial Michael adduct 179 (Scheme 39). 

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