Application Of Tetracoordinate Organoboron In Wittig Olefination

The Wittig olefination reaction is one of the most important methods for thesynthesis of olefins in organic synthesis. In this paper, the reaction ofPh-3P+CH2R(BPh4)(R=CN, COPh, COOEt) with aldehydes in acetonitrile at120C(oil bath temperature)can provide olefins without using an additional base to producethe ylide. This reaction can be carried out in one-pot by heating a mixturePh+3PCH2R(X-)(X=Br, Cl), NaBPh4and aldehydes in acetonitrile, wherePh3P+CH2R(-BPh4) generated from the former two reacts with aldehydesto affordolefins in22%-100%yields. The reaction can undergo smoothly even in the presenceof excess benzoic acid, showing a high tolerance to acid, and provides a new methodfor the olefination of some base-sensitive aldehydes.ArTriolBNBu4is a type of tetracoordinate organoboron compounds to replacearylboronic acid in the Suzuki cross-coupling reaction, and it can be prepared fromthe reaction of arylboronic acid with1,1,1-tris(hydroxymethyl)ethane and then withKOH by azetropic removal of water, followed by anion-exchange with Bu4NOH. Inthis thesis, it is found that ArTriolBNBu4can be synthesized by a one-pot reaction ofarylboronicacid,1,1,1-tris(hydroxymethyl)ethane, and tetrabutylammoniumhydroxide (25%in water) at room temperature, having the advantages of mildconditions and easy operation. It is also found that ArTriolBNBu4is a strong base andcan be employed in all types of Wittig olefination including the reactions ofnon-stabilized, semi-stabilized, and stabilized ylides with aldehydes to afford olefinsin more than80%yields. Comparing with other strong bases such as t-BuOK, NaHand BuLi, ArTriolBNBu4is an air-stable crystalline solid and easy to handle.