Bifunctional is more than twice as fun! At low loading, catalyst 1 (see scheme) can form two important heterocycle classes, apparently by attack of XH on a vinylidene intermediate. Aza‐ and nitroindoles can be formed, and all N‐protecting groups tested (alkyl, allyl, sulfonyl) were tolerated. The newly formed ring can be deuterated in one step, and for substrates with two terminal alkynes, cyclization can be followed by hydration, making this catalyst uniquely versatile.
We report a single bifunctional ruthenium catalyst for cyclization of terminal alkynylaryl amines and -phenols to corresponding indole and benzofuran derivatives in good yields. Key features the ability to cyclize and hydrate terminal alkynes in one step and to deuterate the heteroaromatic compounds formed.
The cyclization of a range of aniline and phenol derivatives to indoles and benzofurans is presented. Advantages of this reaction are the use of only 2 mol% catalyst in most cases and the unprecedented ability of a cycloisomerization catalyst to perform hydration or deuteration in the same reaction. -(NAIR, R. N.; LEE, P. J.; REINGOLD, A. L.; GROTJAHN*, D. B.; Chem. Eur.
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