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Stereoselective Catalytic Synthesis of Alkynylated Phosphaethenes Leading to Activation‐Free Gold Catalysis
Author(s) -
Ito Shigekazu,
Shinozaki Tomokazu,
Mikami Koichi
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201701259
Subject(s) - chemistry , sonogashira coupling , stereoselectivity , alkene , catalysis , aryl , steric effects , combinatorial chemistry , palladium , medicinal chemistry , organic chemistry , alkyl
The π‐accepting property of alkene‐like phosphaethenes (–P=C<) is attractive for the development of Lewis acidic transition‐metal catalysts. The stereoselective monoalkynylation of a sterically encumbered gem ‐dibromophosphaethene by a Sonogashira process has been accomplished, and the corresponding 2‐alkynyl‐2‐bromo‐1‐phosphaethenes were obtained. Subsequent arylation of the 2‐alkynyl‐2‐bromo‐1‐phosphaethenes by the palladium version of the Kumada–Tamao–Corriu (KTC) reaction gave the corresponding 2‐alkynyl‐2‐aryl‐1‐phosphaethenes through an inversion of the configuration. The 2‐alkynyl‐2‐aryl‐1‐phosphaethenes were converted into the corresponding chloro‐gold(I) complexes, and screening of their catalytic activity revealed that both appropriate π‐conjugative substituents and the stereochemistry were decisive for the efficiency of the gold‐catalyzed reactions under activation‐free conditions. Chloro‐gold complexes bearing 2,2‐diaryl‐1‐phosphaethene ligands showed moderate‐to‐good catalytic activity.