Rearrangement of bicyclo[2.2.1]heptane ring systems by titanocene alkylidene complexes to bicyclo[3.2.0]heptane enol ethers. Total synthesis of (.+-.)-.DELTA.9(12)-capnellene
process that involves the Meyer–Schusterrearrangement of alkynols followed by the Diels–Alder cycloaddition of the resulting enones. These reactions were performed under mild conditions in the presence of 5 mol-% of the catalyst to afford the cycloadducts in good yields with almost 100 % endo stereoselectivity. In-depth computational studies of the cycloaddition mechanism provided the preferred geometry
New and Facile Synthesis of Aminobicyclo[2.2.1]heptane-2-carboxylic Acids
作者:Seung-Yong Seo、Dongyun Shin、Taek-Soo Kim
DOI:10.1055/s-0034-1378690
日期:——
b-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid is described. Substrate-controlled α-carboxylation of norbonene monoester delivered the asymmetric diester intermediate with high diastereoselectivity (up to 35:1). Sequential chemoselective ester cleavage, Curtius rearrangement, and hydrolysis gave the a- and b-isomers of 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid, respectively.
Cyanide Anion as a Leaving Group in Nucleophilic Aromatic Substitution: Synthesis of Quaternary Centers at Azine Heterocycles
作者:Alexander D. Thompson、Malcolm P. Huestis
DOI:10.1021/jo302307y
日期:2013.1.18
Nucleophilic aromatic substitution of 2- or 4-cyanoazines with the anions derived from aliphatic α,α-disubstituted esters and nitriles leads to displacement of the cyanide function. Enabling cyanides to be used as highly active leaving groups in SNAr reactions provides additional flexibility in starting materials for synthesis. We show that, in many cases, the cyanide leaving group is displaced preferentially
用衍生自脂族α,α-二取代的酯和腈的阴离子对2-或4-氰基嗪进行亲核芳族取代会导致氰化物官能团的置换。使氰化物能够在S N Ar反应中用作高活性离去基团,为合成原料提供了额外的灵活性。我们表明,在许多情况下,氰化物离去基团在卤素存在下优先被取代。所得的杂芳基碘化物,溴化物和氯化物随后可用作进一步化学多样化的处理方法。
Ultracentrifuge-mediated Diels–Alder Reaction in a Two-phase System of Water and Chloroform
Dramatic acceleration of the Diels–Alder reaction of acrylate ester or methacrolein with cyclopentadiene has been observed under ultracentrifugation conditions in the presence of water, when water–CHCl3 two-phase system was employed. The Diels–Alder reaction proceeds in the lower organic phase under ultracentrifugation-induced high pressure with the upper water phase acting like a weight.
In the asymmetric Diels-Alder reaction of acrylates with cyclopentadiene catalyzed by a series of chiral titanium complexes derived from 2,2'-biaryldiols 1-3, ee's of the endo-adducts depend on the torsional angles of the ligands and are maximal when 1,1'-bi-2-naphthol 1 or 6,6'-hexylenedioxy-2,2'-biphenyldiol 2 e is used. Copyright (C) 1996 Published by Elsevier Science Ltd