Dearomative Allylation of Naphthyl Cyanohydrins by Palladium Catalysis: Catalyst-Enhanced Site Selectivity

Abstract

A dearomative allylation of naphthyl cyanohydrins with allyl borates and allyl stannanes under palladium catalysis was developed. At the initial stage of this study, the dearomative reaction (C4 substitution of the aromatics) was competing with benzyl substitution. To circumvent this issue, the use of palladium and meta-disubstituted triarylphosphine as the catalyst in a 1:1 ratio was found to enhance the site selectivity, furnishing the desired dearomatized products. Further derivatizations of products were also successful.

Development of Novel Methodology Using Diazo Compounds and Metal Catalysts

“…Engineering chemoselectivity in a divergent reaction system using highly reactive species such as metal-carbenes, however, remains a tough challenge. Arene dearomatization reactions [11][12][13] are powerful strategies for constructing three-dimensional molecules from easily accessible aromatic feedstocks. [14][15][16][17] Our group envisioned that chemoselective arene dearomatizations could be designed by applying an electrophilic metal-carbene if the competing C-H insertion and Buchner ring expansion could be suppressed by suitable selection of the metal-center and supporting ligands.…”

Benzyl Palladium Intermediates: Unique and Versatile Reactive Intermediates for Aromatic Functionalization

“…In 2020, the same group developed a dearomative allylation of aromatic cyanohydrins via η 3 ‐allyl palladium intermediates. Different from the previous work, the phosphine ligand was changed from 4‐(diphenylphosphanyl)‐ N , N ‐dimethylaniline to m‐ dimethoxyphenyl phosphine, and the ratio of catalyst to ligand was modified from 1:4 to 1:1 [30] …”

Highly Regioselective Aromatic C–H Allylation of N-(Arylmethyl)sulfonimides with Allyl Grignard Reagents Involving Benzylic C–N Cleavage

“…The aromatic functionalization of benzyl chlorides was later successfully extended to nucleophiles such as allylsilanes, allylboronates, allenylstannanes, active methylene compounds, and amines . Moreover, benzyl phosphates, benzyl carbonates, and benzylammonium salts proved to be alternative benzyl electrophiles via benzylic C–O or C–N cleavage (Scheme a). These methods complement the traditional functionalization of aromatic rings, providing convenient access to complex cyclic nonaromatic and aromatic systems that find wide applications as pharmaceuticals, dyes, catalysts, and organic electronic devices …”