One-Pot Transformation of Trichloroacetamide into Readily Deprotectable Carbamates
摘要:
A trichloroacetamide group was converted to an isocyanate, which was in situ captured by a variety of alcohols in the presence of CuCl and n-BuN4Cl to afford the corresponding carbamates. The scope and limitation of this transformation are also described.
obtained trifluoroacetimidates were more stable than the trichloro analogue and were easily purified by SiO2 column chromatography and/or distillation. The 3,3-sigmatropic rearrangement of allylic analogues, acid-catalyzed cyclization of the epoxy analogues and glycosylation of sugar analogues were studied comparing with their corresponding trichloroacetimidates. The trifluoroacetimidates were considerably
Directed Dihydroxylation of Cyclic Allylic Alcohols and Trichloroacetamides Using OsO<sub>4</sub>/TMEDA
作者:Timothy J. Donohoe、Kevin Blades、Peter R. Moore、Michael J. Waring、Jon J. G. Winter、Madeleine Helliwell、Nicholas J. Newcombe、Geoffrey Stemp
DOI:10.1021/jo026161y
日期:2002.11.1
The oxidation of a range of cyclicallylicalcohols and amides with OsO4/TMEDA is presented. Under these conditions, hydrogen bonding control leads to the (contrasteric) formation of the syn isomer in almost every example that was examined. Evidence for the bidentate binding of TMEDA to OsO4 is presented and a plausible mechanism described.
Trichloroacetamide was transformed into dibenzylguanidinium salt in three steps. Attempted debenzylation was very difficult in the guanidinium form even under high pressure hydrogen and high temperature conditions. On the other hand, the benzyl groups on acetylated guanidine were easily deprotected by hydrogenolysis under 1 atm of hydrogen. These methods were applied to the syntheses of tetrodotoxin-related
Direct Preparation of Guanidine from Trichloroacetamide. A Potentially Important Method to (−)-Tetrodotoxin
作者:Noboru Yamamoto、Minoru Isobe
DOI:10.1246/cl.1994.2299
日期:1994.12
Trichloroacetamides obtained via Overman [3,3] sigmatropic rearrangement were converted into dibenzyl guanidines. The key step was conversion of carbodiimide intermediate into guanidine by scandium or ytterbium trifluoromethane-sulfonates. This method was applied to a synthesis of guanidinium ring of (−)-tetrodotoxin.
Transition metal catalyzed radical cyclization: new preparative route to .gamma.-lactams from allylic alcohols via the [3.3]-sigmatropic rearrangement of allylic trichloroacetimidates and the subsequent ruthenium-catalyzed cyclization of N-allyltrichloroacetamides
A sequence of reactions including [3.3]-sigmatropic rearrangement of allyl trichloroacetimidates (Overman rearrangement) followed by ruthenium-catalyzed cyclization of N-allyltrichloroacetamides provided a novel method for preparing trichlorinated gamma-lactams from allylic alcohols. No delta-lactam was formed as a byproduct. The cyclization of secondary N-allyltrichloroacetamides proceeded with good diastereoselectivity. Two types of tandem cyclizations to form bicyclic lactams took place in the cyclization of N-allyltrichloroacetamides from geraniol and linalool.