Formal Intramolecular (4 + 1)-Cycloaddition of Dialkoxycarbenes: Control of the Stereoselectivity and a Mechanistic Portrait
摘要:
The stereoselective synthesis of 5-5, 6-5, and 7-5 fused O-heterocyclic compounds is reported. The key reaction is a formal intramolecular (4 + 1)-cycloaddition involving a dialkox-ycarbene and an electron-deficient diene where the stereo-selectivity is dependent on the length of the tether. An analysis of the stereochemical outcome of this reaction sheds light on its complex mechanistic picture. High-level calculations were used to support the proposed mechanistic portrait.
Reactions of allyloxy(methoxy)carbene in solution. Carbene rearrangement and Claisen rearrangement of the carbene dimer
作者:Damian Plazuk、John Warkentin、Nick Henry Werstiuk
DOI:10.1016/j.tet.2005.04.024
日期:2005.6
Allyloxy(methoxy)carbene, with and without deuterium in the α-position of the allyloxy group, was generated in benzene at 50 and at 110 °C. At the higher temperature, the carbene fragmented to allyl and methoxycarbonyl radicals that subsequently coupled. At the lower temperature, most of the carbene dimerised. The structure of the major product and the distribution of deuterium indicated that the dimer