| Abstract
| - Four-component coupling process involving two acetylenes, a nitrile, and a divalent titaniumalkoxide reagent, Ti(O-i-Pr)4/2i-PrMgCl, directly yielded titanated pyridines in a highly selective manner.The reaction can be classified into four categories: (i) a combination of an internal acetylene, a terminalacetylene, sulfonylnitrile, and the titanium reagent to yield α-titanated pyridines, (ii) a combination of aninternal acetylene, a (sulfonylamino)acetylene, a nitrile, and the titanium reagent to yield alternativeα-titanated pyridines, (iii) a combination of an internal acetylene, a (sulfonylamino)acetylene, a nitrile, andthe titanium reagent to yield titanated aminopyridines, and (iv) a combination of an acetylenic amide, aterminal acetylene, a nitrile, and the titanium reagent to yield pyridineamides with their side chain titanated.Some of these reactions enabled virtually completely regioselective coupling of two different, unsymmetricalacetylenes and a nitrile to form a single pyridine. Synthetic applications of these reactions have beenillustrated in the preparation of optically active pyridines and medicinally useful compounds.
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