phosphine-catalyzed transformation has been developed for the synthesis of chiral cyclobutene triesters and fluorinated spirocyclic compounds. The strategy involved a P(III)/P(V) redox cycling process, via in situ reduction of phosphine oxide with phenylsilane. This catalytic methodology has enabled the enantioselective synthesis of functionalized cyclobutenes (24 examples, up to 94% ee). On the occasion of the
Catalytic and Asymmetric Process via P<sup>III</sup>/P<sup>V</sup>═O Redox Cycling: Access to (Trifluoromethyl)cyclobutenes via a Michael Addition/Wittig Olefination Reaction
In the present study, we report the first enantioselective and highly efficient phosphine-catalyzed process via a chemoselective in situ phosphine oxide reduction. Starting with 4,4,4-trifluorobutane-1,3-dione and dialkyl acetylenedicarboxylate substrates, highly functionalized fluorinated cyclobutenes were obtained in excellent yields and enantioselectivities. Using the same methodology, CF3-spirocyclobutene
[3+3] Cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes—a new approach to diverse CF3-substituted fluorenes, dibenzofurans, 9,10-dihydrophenanthrenes and 6H-benzo[c]chromenes
作者:Stefan Büttner、Nazken K. Kelzhanova、Zharylkasyn A. Abilov、Alexander Villinger、Peter Langer
DOI:10.1016/j.tet.2012.01.101
日期:2012.5
Trifluoromethyl-substituted fluorenes, dibenzofurans, 9,10-dihydrophenanthrenes and 6H-benzo[c] chromenes were prepared by formal [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes. The reactions proceeded with very good regioselectivity. The product distribution depends on the type of 1,3-dielectrophile employed and can be explained by electronic reasons. (C) 2012 Elsevier Ltd. All rights reserved.
Stereoarrayed CF<sub>3</sub>
-Substituted 1,3-Diols by Dynamic Kinetic Resolution: Ruthenium(II)-Catalyzed Asymmetric Transfer Hydrogenation
CF3‐substituted 1,3‐diols were stereoselectively prepared in excellent enantiopurity and high yield from CF3‐substituted diketones by using an ansa‐ruthenium(II)‐catalyzed asymmetric transfer hydrogenation in formic acid/triethylamine. The intermediate mono‐reduced alcohol was also obtained in very high enantiopurity by applying milder reaction conditions. In particular, CF3C(O)‐substituted benzofused