Gold(i) catalyzed [1,3] O → C rearrangement of benzylvinyl ethers

Abstract

A simple procedure for the preparation of 3-(hetero)arylpropionaldehydes has been developed employing a gold-catalyzed [1,3]-rearrangement of vinyl ethers.

Enantioselective [1,3] O-to-C rearrangement: dearomatization of alkyl 2-allyloxy/benzyloxy-1/3-naphthoates catalyzed by a chiral π–Cu(ii) complex

“…This lack of research is probably due to high activation barriers, since suprafacial [1,3]-sigmatropic rearrangement is an orbital symmetry-forbidden process, and typically requires harsh reaction conditions such as high temperature to proceed through radical intermediate 2. To overcome this limitation, tremendous effort has been devoted to the activation of a substrate by various catalytic systems (transition metal catalysis,3 nucleophilic catalysis4 and Lewis acid catalysis5). Among these systems, Lewis acid catalysis has been most intensively studied.…”

Site-Selective Alkoxylation of Benzylic C–H Bonds via Photoredox Catalysis

“…Water, unfortunately, is not a suitable nucleophile, and overoxidation to the ketone was the major product of this reaction (26). Alcohols of increased steric bulk react more slowly, although the yields of these reactions can be increased using 8 equiv of alcohol (27)(28)(29). A variety of diverse functional groups were readily tolerated (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), including those containing easily oxidizable moieties (30-33, and 37) and potentially base-sensitive groups (36, 38, and 39).…”

“…Isopropoxyethyl)-4-methoxybenzene(27) Prepared according to general procedure C using 1-ethyl-4-methoxybenzene (82.0 mg, 0.600 mmol), isopropyl alcohol (72.2 mg, 1.20 mmol), [Ir(dF(CF3)ppy)2(5,5'-dCF3bpy)]PF6 (6.90 mg, 0.006 mmol), K2HPO4 (312 mg, 1.80 mmol), and Cu(TFA)2(MeCN) (238 mg 0.720 mmol). The crude material was purified by flash column chromatography (5% Et2O/Pentane).…”

“…27 Hz 1H), 0.98 (s, 3H); 13 C NMR (126 MHz, CDCl3) δ 178.03, 159.46, 150.01, 132.13, 127.09, 111.52, 110.72, 77.14, 56.24, 55.23, 51.32, 45.50, 43.62, 38.82, 38.80, 37.34, 28.33, 24.56, 21.83, 19.91.; IR (thin film):           HRMS C20H28O4] requires m/z 355.1880, found m/z 355.1874.…”

Total Synthesis of Propolisbenzofuran B

“…In our initial plan, we opted for direct formylation of the C(2)-carbanion or a C(2) methyl as a surrogate for the formyl group as an alternative, if problems arose in the former approach. To install the key prop-2-en-1-ol unit in 3 , we decided to employ the gold­(I)-catalyzed [1,3] O → C rearrangement of the corresponding allenyl ether, which, in turn, was planned from the propargylic ether 4 . The synthesis of corresponding ketone 5 was planned by following the established methods for the synthesis of 3-aroylbenzofurans that involve the condensation of 2-ethyl-1,4-benzoquinone ( 6 ) with a suitable enaminone. − …”