3 years ago

Convergent synthesis of 4,6-unsubstituted 5-acyl-2-aminodihydropyrimidines using Weinreb amide

Convergent synthesis of 4,6-unsubstituted 5-acyl-2-aminodihydropyrimidines using Weinreb amide
A method of convergent synthesis of novel 4,6-unsubstituted 5-acyl-2-aminodihydropyrimidines 7 is developed. The synthetic intermediate of 7, 4,6-unsubstituted 2-aminodihydropyrimidines 9 having a Weinreb amide at the 5-position, is prepared by the sequential Staudinger/aza-Wittig/cyclization reactions of (E)-tert-butyl{3-azido-2-[methoxy(methyl)carbamoyl]allyl}carbamate (E)-10. The transformation of the Weinreb amide of 9 to an acyl group proceeds smoothly by a substitution reaction using aryllithiums or alkyllithiums in the presence of a catalytic amount of BF3 etherate, affording 7 in good to high yield. The N-protecting group of 7 can be easily removed to obtain N-unsubstituted 2-amino-5-acyldihydropyrimidines 8, and the derivatives are observed as a single isomer in 1H NMR spectroscopy. All dihydropyrimidines in this study were hitherto unavailable and difficult to synthesize by conventional methods.

Publisher URL: www.sciencedirect.com/science

DOI: S0040403917312005

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