synthesize metastable bicyclic 2,5‐dihydrooxepines from cyclic 1,3‐diketones and 1,4‐dibromo‐2‐butenes through the retro‐Claisen rearrangement of syn‐2‐vinylcyclopropyl diketone intermediates is reported. DFT calculations were performed to understand the reaction selectivity and mechanisms towards [1,3]‐ or [3,3]‐sigmatropic rearrangements, highlighting the crucial influence of the temperature. The reaction
An organocatalytic Cloke–Wilson rearrangement of cyclopropyl ketones to 2,3-dihydrofurans is exploited utilizing the homoconjugate addition process. With 1,4-diazabicyclo[2.2.2]octane as the catalyst, the rearrangement in DMSO at 120 °C proceeded in generally high yields, exclusive regioselectivity, and a broad substrate scope. An examination of the mechanism including stereochemical analysis and intermediate
Activation of C–O and C–N Bonds in Allylic Alcohols and Amines by Palladium Complexes Promoted by CO<sub>2</sub>. Synthetic Applications to Allylation of Nucleophiles, Carbonylation, and Allylamine Disproportionation
作者:Masato Sakamoto、Isao Shimizu、Akio Yamamoto
DOI:10.1246/bcsj.69.1065
日期:1996.4
can be achieved by using allylicalcohols directly in the presence of palladium complexes and CO2. Direct carbonylation of allylicalcohols into unsaturated carboxylic acids can be catalyzed by palladium complexes under the pressure of CO and CO2. Disproportionation of diallylamine into triallylamine and allylamine is also catalyzed by palladium complexes in the presence of CO2. On the basis of studies
We report a phosphine‐catalyzed activation of electron‐deficient vinylcyclopropanes (VCPs) to generate an ambident C5 synthon that is poised to undergo consecutive reactions. The utility of the activation is demonstrated in a phosphine‐catalyzed rearrangement of vinylcyclopropylketones to cycloheptenones in good yields with a broad substrate scope. Mechanistic investigations support a stepwise process
Domino [3+3] Annulation/Ring-Cleavage Reactions of 1,3-Bis(trimethylsilyloxy)-1,3-butadienes with 5-Aryl- and 5-Vinyl-3-acyl- 4,5-dihydrofurans: Efficient Synthesis of 5-(4-Chlorobut-2-en-1-yl)- and 5-(2-Aryl-2-chloroethyl)salicylates
The domino “[3+3] cyclization–ring-opening” reactions of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-acetyl-5-vinyl-4,5-dihydrofurans afforded 5-(4-halobut-2-en-1-yl)salicylates. The reactions of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-acetyl-5-aryl-4,5-dihydrofurans gave 5-(2-aryl-2-chloroethyl)salicylates.