Synthesis and easy aromatisation of 5-substituted 6-(alkylthio)-2-methoxy-2,3-dihydropyridines. A new approach to the pyridine ring
作者:Nina A. Nedolya、Nataly I. Schlyakhtina、Lyudmila V. Klyba、Igor A. Ushakov、Sergei V. Fedorov、Lambert Brandsma
DOI:10.1016/s0040-4039(02)02423-1
日期:2002.12
Reaction of lithiated methoxyallene, 1-ethoxyethoxyallene, 1-(methylthio)propyne and 2-butyne with methoxymethyl isothiocyanate, MeOCH2N=C=S followed by methylation affords the imidothioates H2C=C=C(R)C(SMe)=NCH2OMe [R=Me, OMe, OCH(Me)OEt, SMe]. Rearrangement to the fully conjugated Systems H2C=CH-C(R)=C(SMe)-N=CHOMe and subsequent electrocyclisation of these compounds leads to the 5-substituted 6-(methylthio)-2-methoxy-2,3-dihydropyridines with good to excellent yields. In the presence of acidic catalysts or by heating at elevated temperatures these dihydropyridines eliminate methanol to afford 3-substituted 2-(methylthio)pyridines. The aroma compound 2-(methylthio)-3-pyridinol was obtained by acid-catalysed treatment of 3-(1-ethoxyethoxy)-2-(methylthio)pyridine. (C) 2002 Elsevier Science Ltd. All rights reserved.