2- phenyl-4-substituted- 1-pyrroline

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... 

EQUIVALENT IN THE SYNTHESIS OF SUBSTITUTED 1-PYRROLINES 2-PHENYL-1-PYRROLINE (2H-Pyrrole, 3,4-dihydro-5-phenyI-)... 

N-Vinylpyrrolidin-2-one as a 3-Aminopropyl Carbanion Equivalent in the Synthesis of Substituted 1-Pyrrolines Preparation of 2-Phenyl-1-pyrroline. 

With dimethyl fumarate, methyl acrylate, and methyl methacrylate as dipolarophiles, substituted pyrrolines are obtained.52-54 In contrast, the reaction of 2-phenyl-2-oxazolin-5-onium perchlorate with benzyl-ideneaniline follows a different course to give the imidazolin-4-one (24).55... 

Barluenga and coworkers utilized a dilithiation reaction involving allylic amines to prepare 3- and 4-substituted 3-pyrrolin-2-ones (1988TL4859, 1993TL7777). Sequential treatment of allylic amines (e.g., 247) with -butyIlithium, teri-butyllithimn and then diethyl carbonate gives 3-pyrro-Un-2-ones (e.g., 249), presumably via dilithiated intermediates such as 248 (Scheme 61). Yus and coworkers used CO2 as an electrophile in a similar sequence used to prepare l,5-dimethyl-4-phenyl-3-pyrrolin-one (1995 TA2081). 

Additional unsymmetrical porphyrazinols have also been reported. The mixed macrocyclization of the dispiroketal substituted dinitrile (188) with di-terf-butyl phenyl pyrroline (68) gives Mg[pz(AB3)], A = dispiroketal, B = di-terf-butyl phenyl (194) in 30% yield, which can be demetalated with glacial acetic acid to... 

A synthesis of the 17/3-[3-pyrrolin-2-on-4-yl]androstane (361) from acetyl-digitoxigenin (339) has been reported. The conversion of the iV-acetyl compound (362) into dihydrosolacongestidine (363) was improved by use of BU2AIH and thereby improved the synthesis of solacongestidine (364). Addition of diarylnitrilimines to a series of 17-substituted androst-16-enes gave the [16a,17o -f ]-2 -pyrazolines (365) or, when R = OAc, the [16,17-rf]-pyrazoles (366). The pyrazolines (367) were synthesized from 3/3-acetoxy-21-benzylidenepregn-5-en-20-one by reaction with phenyl- or p-methoxyphenyl-hydrazine. " Reaction of cholest-4-en-6-one with hydrazines and o-phenylenediamine led to the heterocyclic structures (368) and (369)... 

When a solution of 3-phenyl-2H-azirine in excess methyl acrylate or acrylonitrile is photolyzed, 2-phenyl-4-substituted-l-pyrroline is obtained (Scheme 5.35). 

At 140 °C, with Pco = 40 Kg/cm, a substrate/catalyst ratio of 20, for 16 h, a complete conversion was observed and the 1-pyrroline was obtained with 91 % selectivity (4-methyl-4-nirto-l-phenyl-1-pentanone as substrate). Substituted phenanthrolines and 2,2 -bipyridine were less effective as cocatalysts. Other ligands performed poorly in this reductive heterocyclisation. 

Cyclic aldo- and ketonitrones react similarly with phenyl isothiocyanateHowever, substituted phenyl isothiocyanates react with 5,5-dimethyl-l-pyrroline-l-oxide to give cycloadducts derived from addition across the C=N bond as well as the C=S bond of the isothiocyanates. The C=S cycloadducts are unstable and undergo further transformations . The [3+2] cycloaddition reaction of 3,3,5,5-tetramethylpyrroline-l-oxide with aryl- and phenylcarbonyl isocyanates also occurs exclusively by addition across the C=S bond . ... 

There are few reports in the literature for the synthesis of 3-pyrrolin-2-ones so a simple method for the preparation of substituted 4-phenyl derivatives from phenylpropiolic ester, dimethyl sulphoxonium methylide and amines is welcome (Scheme 64). T-Azaspiroannelation has been described by Bryson and Wilson, ... 

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