We
report the syntheses of 1,4-diazacycles by diol–diamine
coupling, uniquely made possible with a (pyridyl)phosphine-ligated
ruthenium(II) catalyst (1). The reactions can exploit
either two sequential N-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.
We show the syntheses of the drugs cyclizine and homochlorcyclizine
in 91% and 67% yields, respectively.
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