A general phosphoric acid-catalyzed desymmetrization of meso-aziridines with silylated selenium nucleophiles
作者:Matilde Senatore、Alessandra Lattanzi、Stefano Santoro、Claudio Santi、Giorgio Della Sala
DOI:10.1039/c1ob05837a
日期:——
The first example of meso-aziridine desymmetrization with selenium nucleophiles is reported. The reaction, promoted by VAPOL-hydrogen phosphate using (phenylseleno)trimethylsilane as the nucleophile, proves to be very general and highly enantioselective (84–99% ee).
experimental conditions for the preparation of trimethylsilyl enolethers 3 from α-phenylseleno aldehydes 1, compatible with a limited deselenenylation of the substrate, were studied. Starling from α-phenylseleno ketones 2, the enoxysilanes 4, bearing a vinylic PhSe group, are the major products when triethylamine is the base. Trimethylsilyl enolethers 5 with an allylic PhSe group arc also formed beside 4
A new, efficient method of fluoroselenenylation of terminal, and open-chain symmetric and unsymmetric disubstituted acetylenes and cycloalkynes, gives vicinal (E)-fluoroalkenyl selenides in moderate to high yields by addition of selenenyl fluoride equivalents. These are formed in situ from xenon difluoride and diaryl, dibenzyl or primary and secondary dialkyl diselenides. Alternatively, the benzeneselenenyl fluoride equivalent is formed by treatment of more reactive phenylselenotrialkylsilanes with xenon difluoride. The regiochemistry of the addition is strongly dependent on the steric effects of substituents bonded to the acetylene.
<i>p</i>-Silylation of Arenes via Organic Photoredox Catalysis: Use of <i>p</i>-Silylated Arenes for Exclusive <i>o</i>-Silylation, <i>o</i>-Acylation, and <i>o</i>-Alkylation Reactions
Photocatalytic regiospecific p-silylation of arenes has been achieved by the coupling of in situ generated silyl radical with areneradicalcation. The strategy involves reductive activation of PhSe–SiR3 and single electron transfer from the electron rich arene to 9,10-dimethoxyanthracene radicalcation (DMA•+). p-Silyl arenes, thus formed, are further utilized for exclusive o-silylation reaction and
Synthesis of enantiomerically enriched β-hydroxy selenides by catalytic asymmetric ring opening of meso-epoxides with (phenylseleno)silanes
作者:Marcello Tiecco、Lorenzo Testaferri、Francesca Marini、Silvia Sternativo、Francesca Del Verme、Claudio Santi、Luana Bagnoli、Andrea Temperini
DOI:10.1016/j.tet.2008.01.126
日期:2008.4
The first example of the enantioselectivering opening of meso-epoxides by (phenylseleno)silanes using salen(Cr)complexes as catalyst is described. This desymmetrization reaction constitutes a simple and convenient approach to synthetically versatile optically active β-hydroxy selenides.