作者:Wolfgang Kirmse、Pham van Chiem、Paul-Georg Henning
DOI:10.1016/s0040-4020(01)96385-9
日期:1985.1
opylidenes (95,97) were generated from the corresponding nitrosoureas in methanol at room temperature. The diazo route is initiated by the formation of 2-vinylcyclopropanediazonium ions (e.g.43) which do not undergo 1,3-carbon shifts. No cyclopentenyl products were found in weakly basic methanol where the diazonium ions prevail. Ring opening of the diazonium ions gives pentadienyl cations and products
Production of orbitally forbidden products in the IR-laser-induced isomerization of cis-3,4-dichlorocyclobutene
作者:Chung-Rei Mao、Nathan Presser、Lian-Shun John、Robert M. Moriarty、Robert J. Gordon
DOI:10.1021/ja00398a046
日期:1981.4
the net result of many chiral centers is optical yields approaching 100%. Finally, we suggest a method for increasing optical yields in asymmetric induction for natural product synthesis. Where a concerted reaction is involved in the synthesis, we may study the effect of individual chiral prosthetic groups at different sites in the molecule and predict which combination will lead to the highest optical
Infrared multiphoton induced isomerization of <i>cis</i>‐3,4‐ dichlorocyclobutene. I. Experimental results
作者:Nathan Presser、Chung‐Rei Mao、Robert M. Moriarty、Robert J. Gordon
DOI:10.1063/1.444618
日期:1983.5.15
The yield and product distribution in the laser-induced isomerization of cis-3,4-dichlorocyclobutene (DCCB) have been measured as functions of laser fluence, DCCB pressure, and buffer gas pressure. Both Woodward–Hoffman allowed and ‘‘forbidden’’ isomers were observed. The fraction of ‘‘forbidden’’ products was found to increase linearly with fluence above a threshold of 3.5 J/cm2. At high fluence the yield increased quadratically with neat DCCB pressure. Both the yield and fraction of ‘‘forbidden’’ products declined monotonically with buffer gas pressure. These observations are explained in terms of a two-channel mechanism, in which the allowed isomer is formed in a concerted path and the forbidden isomers are produced from a diradical intermediate in a nonconcerted reaction.
Braye,E.H., Bulletin des Societes Chimiques Belges, 1963, vol. 72, p. 699 - 705