Shun-ya Onozawa

Lanthanoid-catalysed Tishchenko reaction of mono- or di-aldehydes

Abstract Lanthanoid complexes are found to be very active catalysts for the Tishchenko reaction of aldehydes. In the presence of Cp∗2LnCH(SiMe3)2 (Ln = Nd, La), esters are obtained from corresponding monoaldehydes in high yields. This method is applicable to dialdehydes. The reaction of o-phthalaldehyde proceeds intramolecularly to give phthalide quantitatively. Terephthalaldehyde and di(4-formylphenyl) ether are cleanly converted into the poly[p-(carboxymethylene)phenylene] (II) and poly[p-(carboxymethylene)(p-phenylenoxy)phenylene] (III), respectively. On the other hand, isophthalaldehyde polymerizes first and then the polymer is transformed into a macrocyclic lactone 1,5,11-trioxo-2,4;8,10;14,16-tribenzo-6,12,18-trioxacyclooctadecane (I-a) in high yields. The 18-membered macrocyclic structure of I-a was determined by the X-ray analysis. Stoichiometric reactions of the La complex with benzaldehyde indicated the intermediacy of alkoxo complexes in the catalysis.

Hydrosilation of dienes catalyzed by Cp*2NdCH(SiMe3)2

Abstract Cp*2NdCH(SiMe3)2 efficiently catalyzes hydrosilation of 1,3-, 1,5-, and 1,6-dienes under mild conditions with unusual selectivities as compared with later transition metal-catalyzed reactions; hydrosilation of isoprene affords mainly (E)-, not (Z)-, allylsilane. On the other hand, hydrosilation of 1,5- and 1,6-dienes proceeds through intramolecular CC bond formation to give (silylmethyl)-cyclopentanes.

REGIO- AND STEREOSELECTIVE 1,4-BORYLSTANNATION OF 1,3-DIENES PROMOTED BY PALLADIUM CATALYSTS

Abstract Regio- and stereoselective 1,4-addition of borylstannane 2 to 1,3-dienes smoothly preceeds in the presence of catalytic amounts of Pd 2 (dba) 3 and P(OCH 2 ) 3 CEt, giving high yields of (Z)-1-boryl-4-stannyl-2-butenes 3 . The reaction of 3 with aldehyde provides a facile method for preparing various homoallyl alcohols.

Palladium-catalysed borylsilylation and borylstannylative dimerization of 1,2-dienes

A borylsilane regioselectively adds to 1,2-dienes in the presence of palladium complexes to afford high yields of alkenylboranes having allylsilane moieties, whereas a borylstannane gives a 1 : 2 telomer with 3-methylbuta-1,2-diene due to borylstannylative dimerization.

PALLADIUM-CATALYSED BORYLSILYLATION OF ALKYNES AND BORYLSILYLATIVE CARBOCYCLIZATION OF DIYNES AND AN ENYNE COMPOUND

Addition reactions or addition–carbocyclization reactions of a borylsilane with alkynes, α,ω-diynes or an enyne compound proceed efficiently in the presence of palladium catalysts, P(OCH 2 ) 3 CEt being the ligand of choice.

Ring-opening polymerization of ε-caprolactone with yttrium triflate

A simple and green procedure for bulk polymerization of e-caprolactone (CL) has been developed using yttrium triflate (trifluoromethanesulfonate) as a catalyst under air in a simple glass vial. The efficiencies of various initiators such as diol or triol with acid or base were discussed. Little water was found to be necessary in this polymerization system. The biodegradation of direct molded poly(e-caprolactone) (PCL) film during polymerization in aqueous solution with commercial compost was also studied by measuring the biochemical oxygen demand (BOD).