One-pot synthesis of 6-aryl-2,3-dihydro-4H-pyran-4-ones by cyclocondensation of 1,3-diketone dianions with aldehydes

Asymmetric Aldol/Vinylogous Aldol/Cyclization Reaction Using Phosphine Oxide Catalysts

Chiral phosphine oxide sequentially activates silicon tetrachloride and trichlorosilyl enol ethers to facilitate asymmetric aldol/vinylogous aldol reaction of 4-methoxy-3-penten-2-one and conjugated aldehydes in a highly enantioselective fashion, and the subsequent cyclization produced optically active 2,6-disubstituted 2,3-dihydro-4-pyranones bearing stereogenic centers at a remote position in a single operation.

Two new phenols from Scutellaria barbata

Two new phenols, 2(S)-2’,7-dihydroxy-5,8-dimethoxyflavanone (1) and (S)-2-(4-hydroxyphenyl)-6-methyl-2,3-dihydro-4H-pyran-4-one (2), were isolated from the ethanol extract of Scutellaria barbata. Their structures were elucidated on the basis of spectroscopic analysis.

Cobalt-catalyzed 1,4-hydrovinylation of allylsilane and allylboronic esters for the synthesis of hydroxy-functionalized 1,4-dienes

The cobalt(I)-catalyzed 1,4-hydrovinylation reaction of allyl trimethylsilane and allyl pinacol boronic ester with symmetrical and unsymmetrical 1,3-dienes generates building blocks for the in situ allylboration or the Lewis acid induced allylation reaction utilizing the corresponding allyl silane derivatives. The products of these three-component reactions are hydroxy-functionalized 1,4-dienes which can be used for the synthesis of pyranones. An alternate reaction sequence for the synthesis of the hydroxy-functionalized 1,4-dienes by performing the allylation first followed by the cobalt-catalyzed 1,4-hydrovinylation is also possible. Accordingly, polyfunctionalized complex structures can be generated by both approaches in a convergent fashion.