Heteroatom Influence on the π-Facial Selectivity of Diels−Alder Cycloadditions to 1-Oxa-4-thia-6-vinylspiro[4.5]dec-6-ene, 3-Methoxy-3-methyl-2-vinylcyclohexene, and 3-Methoxy-2-vinylcyclohexene<sup>,</sup>
作者:Veejendra K. Yadav、Govindaraji Senthil、K. Ganesh Babu、Masood Parvez、Jennifer Lee Reid
DOI:10.1021/jo0106400
日期:2002.2.1
orbital on the acetal oxygen and the orthogonal pi-orbital of the acetylene unit in DMAD in the syn-to-oxygen addition of the latter. This repulsion is offset on coordination of Li+ to the said oxygen electron pair orbital, and the addition thus proceeds syn to oxygen. The enhanced and accelerated syn-to-oxygen addition in lithium perchlorate in nitromethane is interpreted as a consequence of the coordination