Enantioselective Palladium‐Catalyzed Insertion of α‐Aryl‐α‐diazoacetates into the OH Bonds of Phenols

Abstract

A palladium-catalyzed asymmetric O-H insertion reaction was developed. Palladium complexes with chiral spiro bisoxazoline ligands promoted the insertion of α-aryl-α-diazoacetates into the O-H bond of phenols with high yield and excellent enantioselectivity under mild reaction conditions. This palladium-catalyzed asymmetric O-H insertion reaction provided an efficient and highly enantioselective method for the preparation of synthetically useful optically active α-aryl-α-aryloxyacetates.

Planar Chiral [2.2]Paracyclophane-Based Bisoxazoline Ligands: Design, Synthesis, and Use in Cu-Catalyzed Inter- and Intramolecular Asymmetric O–H Insertion Reactions

“…Considering the similarity between O-H insertion and N-H insertion, and the observation that the preferred absolute stereochemistries of all products (ethanolic O-H insertion product 3, intramolecular aliphatic O-H insertion product, 35) and inter-and intra-molecular aromatic O-H insertion products 9 and 11) obtained with the Box (S p )-1-Cu catalysts are opposite to those obtained with Zhou's Spirobox (S a ,S,S)-5-Cu, 22,[24][25][26] the C 2 -symmetric catalyst conformation during the Cu-catalyzed O-H insertion reaction is proposed to be that shown in Fig. 3b.…”

“…[15][16][17] The Cu-catalyzed O-H insertion of α-diazo esters is useful for the construction of α-alkoxycarbonyl structures, which are found in natural products and biologically active compounds. [18][19][20] A highly enantioselective version of this reaction has recently been accomplished with bisazaferrocene I, 21) Spirobox II, 17,[22][23][24][25][26] or the imidazoindolephosphine ligand III [27][28][29][30][31][32][33][34] (Fig. 2).…”

(C6F5)3B Catalyzed Chemoselective and ortho‐Selective Substitution of Phenols with α‐Aryl α‐Diazoesters

“…[2] However,direct CÀHbond substitution reactions of aromatic compounds with XÀH bonds,s uch as phenols,w hich are widely found in numerous natural products,bioactive compounds,pharmaceuticals,and polymers and also constitute common versatile building blocks in organic synthesis, [3] are rather challenging as XÀH insertion is more favorable in the presence of various metal catalysts,s uch as those based on Rh, Cu, Ru, Fe,o rP d (Scheme 1). [4] TheF u [5] and Zhou [6] groups have developed elegant metal-catalyzed enantioselective versions for this type of reaction. Thedevelopment of methods for the site-selective C À Hbond substitution of phenols,onthe other hand, has long been considered as an attractive but challenging task.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…Selective allylic C-H olefination was observed using α-diazoesters and a two-metal catalyst system of palladium and chromium(III) (the role of chromium was ascribed to activation of the diazo compound through Lewis acid complexation) [1162]. A significant kinetic isotope effect was noted in palladium-catalyzed O-H insertion reactions of diazoderived palladium-carbene complexes [1163]. Palladium-catalyzed coupling of α-diazo carbonyl compounds and vinylboronic acid derivatives afforded α-alkenylation products via carbene intermediates [1164].…”