Fundamental Research for Developing Organotin Reagent

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Research to establish the utility of organotin compounds as synthetic reagents gave the following new findings. (1). Application of Pd(O) catalyzed coupling reaction to heteroaromatics. Thienyl and pyridyl bromide were fond to couple with organotin reagents which can react with bromobenzene in the presence of Pd(PPh_3)_4, but not with those tin compounds which need the catalyst PdCl_2(Po-tol_3)_2 for the coupling with bromobenzene. The coupling of thienyl and pyridyltin compounds with heteroaryl bromides provides good tools for syntheses of heterobiaryls, heteroteraryls, and heteroquateraryls. (2). Coupling reactions of temary systems catalyzed by transition metal complexes. Coupling reactions of organotins and halides involving insertion of third components such as isonitrile and norbornene were found to take place under catalysis of palladium, giving imines and exo,cis-2,3-disubstituted norbomane, respectively. (3). Addition to carbonyls via transmetalation with TiCl_4.2-Stannylcarbonylates were found to react with aldehydes in the presence of equimolar amount of TiCl_4. The reaction giving gamma-lactones after hydrolytic treatment. Stannylamide, 2-(2-stannyl)pyridine and N-stannyl-p- medioxypropiophenone reacted similarly. The reaction proceeds via transmetalation giving titanium compounds stabilized by intramolecular coordination of N or 0 to Ti.