Acyl salts

A -Acyl salts of nitrogen heterocycles phosphorylate in the hetero-ring, rather than at the carbonyl group, to give, for example, (25). The addition of dialkyl phosphites to ynamines has been reported. The products... 

Asymmetric synthesis using W-acyl salts of pyridine and derivatives continues to be developed. The chiral. V-acylpyridinium salt 132 reacts with lithiated ethyl propiolate to provide the diastereomer 133 in 70% yield and... 

This means that the chiral catalyst participates in nucleophilic attack on an achiral acyl donor to afford a reactive chiral acyl salt. Nucleophilic attack on this salt by an appropriate nucleophile (an alcohol, amine or 7r-nucleophile) then provides the acylated product and regenerates the catalyst. This latter step determines the stereochemistry, but knowledge of the precise mechanism by which stereochemical information is transferred in most of these processes is still rather limited. 

Addition of pyrrolyl and indolyl Grignard reagents to 1-acyl salts of 4-methoxy-3-(triisopropylsilyl)pyridine affords the corresponding l-acyl-2-heteroaryl-2,3-dihydro-4(17/)-pyridones, e.g., 443 (main product) and 444... 

Pyridines, quinolines,50 isoquinolines,51 and imidazoles52 react with allylstannanes in the presence of acyl halides, via the corresponding (V-acyl salts, to give the l-acyl-2-allyl derivatives of the 1,2-dihydro compounds. 

Purines react with acylating agents such as chloroformates or diethyl pyrocarbonate to give non-isolable A -acyl salts, which can suffer various fates following nucleophilic addition products of cleavage of either ring have been observed, as have recyclisation products. 

Nucleophilic addition of 6-aryl-2,3-dihydroimidazo[2,l-A]thiazole to phthalazine can be achieved via an A-acyl salt of phthalazine (Scheme 15). This reaction is not restricted to the 4-fluorophenyl... 

Acylation of a ring nitrogen in the fully conjugated pyrimidine derivative leads to a pyrimidinium salt. The A-acyl salts (75) are powerful acylating agents (Scheme 6). In the acylation of tautomeric... 

Condensations at the 5-Methylene Group.— Thiazolidinones undergo direct heteroarylation under the influence of N-acyl salts of six-membered nitrogen heterocycles. Thus, N-acylisoquinolinium salts convert the appropriate thiazolidinone into products of type (244), or 3-phenyliso-rhodanine into (245). Several other heterocyclic patterns (including quinolinium, pyridinium, and acridinium salts) were employed successfully in the production of analogous structures. 5-(2-Oxo-3-indolinylidene)-3-aryl-2-phenyliminothiazolidin-4-ones (246), of thioindigoid character, are formed by the condensation of thiazolidin-4-ones and isatin. ... 

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