Development of novel regio- and stereoselective ring opening of heterocyclic compounds

The development of stereoselective reactions that permit the selective generation of different products from the same precursor simply by varying the reaction conditions or the catalysts are at the center of academic and synthetic interest. We have focused our attention on [2.2.2]-acylnitroso bicyclic systems N-Boc or N-Cbz protected in a copper-catalyzed alkylative ring-opening reactions with organometallic reagents to give new substituted cyclohexenyl hydroxamic acids with a definite stereo- and regioselectivity. We also examined the regio- and stereoselective ring opening of hetero [2.2.1]Diels-Alder cycloadducts with different nucleophiles and trans-1,2-disubstituted cyclopentenes or trans-1,4-disubstituted monoprotected hydrazine cyclopentenes were obtained. The ring opening of aziridines with carbon or boron nucleophiles represents a useful entry into substituted amines. An unprecedent mild nickel-catalyzed ring opening of cyclic vinyl epoxides and aziridines with bis(pinacolato)diboron were achieved to afford new functionalized allylic boron derivatives that can be easily oxidized or trapped in a one-pot procedure with aldehydes. Moreover, the regioselective ring-opening of N-protected 2-phenylaziridines was accomplished by the addition of organoalanes in dichloromethane and this process occurred via completely selective attack of the methyl fragment at the benzilic position. The direct addition of unmodified carboxylic acid anhydrides to the pyridine nucleus has very little precedents and the yields were very low. We have developed a novel copper-catalyzed Perkin acyl-Mannich reaction of pyridine and acetic anhydride for the synthesis of N-acetyl-1,2-dihydropyridine acetic acid. The1,2-dihydropyridine obtain is a valuable building block for the synthesis of very interesting systems such as isoquinuclidines and azasugar derivatives.