Stereoselective radical addition of an acetal to sterically tuned enantiomerically pure N-sulfinyl imines.

Enantiomerically enriched sulfonamides were synthesized by the radical addition of an acetal to enantiomerically pure N-sulfinyl imines using dimethylzinc-air and boron trifluoride diethyl etherate. Higher levels of stereocontrol were observed by using a mesitylenesulfinyl group. Furthermore, an amine and an amino alcohol with high enantiomeric purity were obtainable from the sulfonamide product.

Chemoselective conjugate addition of dimethylzinc-mediated ether and acetal radicals to alkylidenemalonates and asymmetric reactions.

Cyclic and acyclic ether or acetal radicals were generated directly from ethers or acetals by the action of dimethylzinc-air, and their subsequent conjugate addition reaction with alkylidenemalonates afforded the corresponding conjugate adducts in reasonably high yields. The reaction with benzylidenemalonates bearing formyl and imino groups gave chemoselectively the conjugate addition products. The asymmetric reaction of bis(8-phenylmenthyl) benzylidenemalonate proceeded diastereoselectively to provide the adduct with 93:7 dr.

Tin-free radical addition of acyloxymethyl to imines.

Acyloxymethyl radicals were generated from the corresponding iodomethyl esters and successfully underwent addition to the CN bond of N-Ts, N-PMP, and N-Dpp imines by the action of dimethylzinc or triethylborane. Ethyl acetate, toluene, and benzene as well as dichloromethane were suitable solvents. The utility of acyloxymethyl radicals as a hydroxymethyl anion equivalent was highlighted by the facile hydrolysis of the acyloxy moiety of the adducts to give the corresponding amino alcohol derivatives in good to high yield.

Asymmetric radical addition of ethers to enantiopure N-p-toluenesulfinyl aldimines, mediated by dimethylzinc-air.

Asymmetric radical addition of ethers to enantiopure aromatic N-p-toluenesulfinyl aldimines has been achieved. The requisite radicals were generated by dimethylzinc-air. Lewis acid activation of the N-p-toluenesulfinyl aldimines followed by radical addition gives a mixture of sulfinamide and sulfonamide products.

Tin-free intermolecular addition of primary alkyls to imines via the dimethylzinc-air radical process.

[reaction: see text] A dimethylzinc-air initiator was applied to the generation of primary alkyl radicals from alkyl iodides. The addition of the generated primary alkyl radicals to N-tosylimines was accelerated by the action of boron trifluoride-diethyl etherate and copper(II) triflate to give the corresponding adducts in good yields after 2-3 h. Air oxygen was essential for the reaction to proceed, showing involvement of a radical process in the reaction.

Introduction of functionalized C1, C2, and C3 units to imines through the dimethylzinc-air-initiated radical addition.

Introduction of functionalized C1, C2, and C3 units to imines was achieved by using the dimethylzinc-air-initiated alpha-alkoxyalkyl radical addition as a key reaction. The addition to a C[double bond]N double bond chemoselectively occurred in the presence of a C[double bond]O double bond, which is one of the advantages of this radical addition reaction over ionic addition reactions.