Functional Group Manipulation via Organoselenium- and Halogen-Induced Cyclofunctionalization/Hydrolysis of Allylic Benzimidates, Tertiary Benzamides, and Benzamidines. Regioflexible Synthesis of Amino Alcohol Derivatives

Article abstract of DOI:10.1021/jo00061a009

Allylic benzimidates were treated with benzeneselenenyl halides in chloroform or acetonitrile to give, via 5-exo cyclofunctionalization/hydrolysis, 3-(benzoyloxy)-2-(phenylamino)-1-(phenylselenenyl-alkanes in fair yields.Allylic tertiary benzamides afforded 2-(benzoyloxy)-3-(phenylamino)-1-(phenylselenenyl)alkanes when submitted to similar reaction conditions.Bromoalkanes, functionalized in an analogous way, were obtained after hydrolytic workup when bromine was added to allylic benzimidates and tertiary benzamides.In some of these reactions, products of 6-endo cyclofunctionalization/hydrolysis (1-(benzoyloxy)-3-(phenylamino)-2-bromoalkanes) were also formed.The addition of benzeneselenenyl bromide to some α-substituted allylic benzimidates and tertiary benzamides was diastereoselective (0 < de < 90 percent, depending on conditions) with a preference for threo isomer formation.Hydrodeselenation/hydrodebromination of the cyclofunctionalization/hydrolysis products was efficiently effected (88 - 100 percent yield) by treatment of the products with triphenyltin hydride in refluxing benzene containing a catalytic amount of azobis(isobutyronitrile).The proper choice of allylic benzimidate/tertiary benzamide allowed the preparation of amino alcohol derivatives in which the 1,2-orientation of the functional groups, relative to the carbon backbone, could be varied in a controlled and predictable manner.The regioflexibility of the process was demonstrated for primary, secondary, and tertiary positions.When allylic benzamidines were submitted to the cyclofunctionalization/hydrolysis reaction conditions using benzeneselenenyl bromide as the electrophilic reagent, 5-phenyselenenyl(methyl)-substituted dihydroimidazoles were obtained.