Diastereofacial Selectivity in 1,3-Dipolar Cycloaddition to Methylphenylvinylphosphine Oxide

Article abstract of DOI:10.1021/jo00274a022

1,3-Dipolar cycloaddition reactions of nitrile oxides and nitrones with racemic methylphenylvinylphosphine oxide (1) have been found to provide phosphinylisoxazolines and -isoxazolidines, respectively, in very good yields. 5-Substituted regioisomers either prevailed in the product mixtures or were the only product formed.The studied cycloadditions have been found to occur with considerable (ca. 40percent de) diastereofacial selectivity, which compares very well with similar literature data recorded for other chiral allylic systems.Possible transition-state structures are proposed and discussed in terms of conformational preferences about the carbon-phosphorus bond to the alkene in the ground state, in the transition state, and in the product.The crystal structure of 3a has been determined to confirm the spectral assignments; 3a has the erythro configuration and exists in a conformation possessing the C-O and P=O bonds in the anti arrangement.