Coupling of acetylene, nitrile, and a titanium reagent, Ti(O-i-Pr)(4)/2 i-PrMgCl, generated new azatitanacyclopentadienes in a highly regioselective manner. Their subsequent reaction with sulfonylacetylene afforded pyridyltitanium compounds, which, upon reaction with electrophiles, gave substituted pyridines virtually as a single isomer. When optically active nitriles were used in this reaction, chiral pyridines were obtained without loss of the enantiopurity. Alternatively, the azatitanacyclopentadiene prepared from an unsymmetrical acetylene reacted with an aldehyde or another nitrile to give furans or pyrroles having four different substituents again in a regioselective manner.

Silylmethyl, tertiary-alkyl, alkenyl, and aryl Grignard reagents underwent intermolecular addition to olefins, such as styrenes, conjugated dienes, and enynes under an air atmosphere to give homologated alcohols. For example, (trimethylsilyl)methylmagnesium chloride and alpha-methylstyrene in ether at room temperature under dry air directly furnished 2-phenyl-4-(trimethylsilyl)-2-butanol in good yield. As the Grignard addition to olefins under argon with rigorous exclusion of O2 did not proceed at all, the above reaction should involve a radical mechanism: an alkyl radical generated by the aerial oxidation of the Grignard reagent adds to olefin, which is followed by oxygenation. Representative examples of this transformation, where products were obtained in good to excellent diastereo- or regioselectivity, are also disclosed.

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Reactions of organo-metal compoundsO 0350 Facile Preparation of Various Heteroaromatic Compounds via Azatitanacyclopentadiene Intermediates. -Polysubstituted pyridines, furans, and pyrrolecarboxaldehydes are available. The reaction is highly regioselective. Starting from chiral nitriles, convenient synthesis of optically active pyridines is possible. -(SUZUKI, D.; NOBE, Y.; WATAI, Y.; TANAKA, R.; TAKAYAMA, Y.; SATO*, F.; URABE, H.; J. Am. Chem. Soc. 127 (2005) 20, 7474-7479; Dep. Biomol. Eng., Fac. Biosci. Biotechnol., Tokyo Inst. Technol., Midori, Yokohama 226, Japan; Eng.) -Jannicke 40-075