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

Construction of the biaryl-part of vancomycin aglycon via atropo-diastereoselective Suzuki-Miyaura coupling

An atropo-diastereoselective synthesis with diastereomeric ratio up to 98/2 towards the biaryl subunit of vancomycin based on the use of enantiopure β-hydroxysulfoxide derivs. as novel chiral auxiliary is reported

Modular synthesis of cyclic cis- and trans-1,2-diamine derivatives

Structurally diverse carbocycles with two vicinal nitrogen-substituents were prepared in expedient three-component reactions from simple amines, aldehydes, and nitroalkenes. trans,trans-6-Nitrocyclohex-2-enyl amines were obtained in a one-pot domino reaction involving condensation, tautomerisation, conjugate addition, and nitro-Mannich cyclisation. Upon employment of less nucleophilic carboxamides, a concerted Diels–Alder cycloaddition mechanism operated to give the corresponding cis,trans-nitrocyclohexenyl amides. Both types of substituted carbocycles offer ample opportunities for chemical manipulations at the core and periphery. Ring oxidation with MnO2 affords substituted nitroarenes. Reduction with Zn/HCl provides access to various trans- and cis-diaminocyclohexenes, respectively, in a straight-forward manner. With enantiopure secondary amines, a two-step synthesis of chiral nitrocyclohexadienes was developed (82–94% ee)