| Research Abstract |
This research has developed new styles of the Reppe reaction, which afford single aromatic compounds as a titanated form from three different, unsymmetrical acetylenes. Alternatively, replacing one or two acetylene(s) above with nitriles, we also developed an aza-Reppe reaction, producing metalated pyridines or pyrroles as a single isomer. Moreover, some biologically active compounds or medicinally important compounds were prepared by these new reactions. Thus, 1)benzyltitanium compounds were obtained as a single isomer from acetylenic esters, terminal acetylenes, a divalent titanium alkoxide reagent (Ti(O-i-Pr)_4/2 i-PrMgCl (1)), and propargyl bromides. This reaction was applied to the first synthesis of alcyopterosin A and an efficient synthesis of an aromatic moiety of an anti-cancer agent, pradimicin. 2)α-Pyridyltitanium compounds were obtained as a single isomer from acetylenic amides, terminal acetylenes, the titanium reagent 1, and a sulfonylnitrile. This reaction was applied to the synthesis of an antiallergic substance, benzocycloheptapyridine. 3)Pyridinecarbaldehydes were obtained as a single isomer from acetylenic amides, terminal acetylenes, the titanium reagent 1, and nitriles. 4)α-Pyridyltitanium compounds were obtained as a single isomer from acetylenes, nitriles, the titanium reagent 1, and a sulfonylacetylene. Starting this reaction with optically active nitriles, we attained an efficient preparation of an optically active pyridine unit of cyclothiazomycin. 5)Aminopyridines were obtained as a single isomer from acetylenes, (sulfonylamino)acetylenes, the titanium reagent 1, and nitriles. 6)Pyrrolecarbaldehydes were obtained as a single isomer from unsymmetrical acetylenes, the titanium reagent 1, and two different nitriles.
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