Transformation of 5-Oxo Substituted Fused Pyran-2-ones. Lactam Versus Hydrazone Formation
摘要:
6,7-Dihydrocyclopenta[b]pyran-2,5-dione 1 was converted with hydrazines to fused pyridine-2(1H)-ones of type a. In contrast, 2H-1-benzopyran-2,5-diones 2-4 gave under the same reaction conditions 5-hydrazonobenzopyrans of type b. Calculated heats of formation matched experimental findings.
AbstractEthyl vinyl ether was found to be an appropriate synthetic equivalent of acetylene for a set of Diels–Alderreactions with fused pyran-2-ones that yield fused carbocyclic systems. Transformations were conducted under microwave irradiation with DABCO (as a catalyst for the elimination of ethanol) and with n-butanol as the additive. A single-crystal X-ray diffraction structure is presented for
Regioselectivity in the Schmidt Reaction: First Synthesis of Pyrano[3,2-b]azepines
作者:Marijan Kočevar、Franc Pozgan、Slovenko Polanc
DOI:10.3987/com-01-s(k)53
日期:——
The Schmidt reaction of 5,6,7,8-tetrahydro-2H-1-benzopyran-2-ones (1) has been investigated. Derivatives of pyrano[3,2-c]azepines (2) and isomeric pyrano[3,2-b]azepines (3) were isolated by the application of trimethylsilyl azide or sodium azide in a methylene chloride or a chloroform solution in the presence of sulfuric acid At low temperature products (2) were almost sole products, while at higher