Atropodiastereoselective C-H Olefination of Biphenyl p-Tolyl Sulfoxides with Acrylates

A stereoselective method for the synthesis of axially chiral biaryl scaffolds by C-H bond functionalization was accomplished using chiral sulfoxide both as the directing group enabling the regioselective activation of a C-H bond and as the chiral auxiliary generating an asym. environment in the coordination sphere of the metal complex. We have demonstrated the directing ability of the p-tolylsulfinyl group in promoting the Pd(II)-catalyzed C-H olefination of biphenyls. Thus, reacting biphenyl p-tolyl sulfoxide I (R = H) as a mixt. of atropisomers with Me acrylate in the presence of Pd(OAc)2 gave coupling product I [R = (E)-CH:CHCO2Me] in 87% yield (4.6:1 d.r. SaR:SaS)

Visible-Light-Triggered, Metal- and Photocatalyst-Free Acylation of N-Heterocycles

A photoinduced acylation of N-heterocycles is explored. This visible-light triggered reaction occurs not only under extremely mild reaction conditions, but also does not require the presence of a photosensitizer. The mechanistic studies suggest formation of EDA complexes prompt to harness the energy from visible-light. Compatibility with a large panel of α-keto acids as acyl precursors and an array of N-heterocycles clearly showcase the synthetic potential of this handy and green acylation protocol

Highly Efficient One-Pot Access to Functionalized Arylboronic Acids via Noncryogenic Bromine/Magnesium Exchanges

A general and convenient protocol for the electrophilic borylation of aryl Grignard reagents prepd. from arylbromides by direct insertion of Mg in the presence of LiCl or by Mg/Br exchange with iPrMgCl·LiCl was developed. Various aryl boronic acids were synthesized in a straightforward manner in excellent yields at 0°. E.g., reaction of mixt. of 4-bromoanisole, Mg turnings, LiCl in THF with DIBAL-H catalyst followed by the addn. of trimethylborate at 0° gave 92% yield of 4-MeOC6H4B(OH)2

Aryne-mediated fluorination: Synthesis of fluorinated biaryls via a sequential desilylation-halide elimination-fluoride addition process

An unusual aryne-mediated fluorination of arom. ring systems during the desilylation of ortho-bromo-biphenyl-trimethylsilanes with tetrabutylammonium fluoride (TBAF) is described. In situ formation of an aryne and addn. of fluoride affords fluorinated biphenyls. The structures have been confirmed by synthesis of authentic samples via Suzuki-Miyaura cross-coupling and X-ray anal. In situ trapping expts. with furan proved the transient formation of aryne by fluoride-induced displacement of the TMS group and subsequent bromide elimination