Synthesis of 1,4-Diazacycles by Hydrogen Borrowing.

We report the syntheses of 1,4-diazacycles by diol-diamine coupling, uniquely made possible with a (pyridyl)phosphine-ligated ruthenium(II) catalyst (). The reactions can exploit either two sequential -alkylations or an intermediate tautomerization pathway to yield piperazines and diazepanes; diazepanes are generally inaccessible by catalytic routes. Our conditions tolerate different amines and alcohols that are relevant to key medicinal platforms.