AcceptorlessDehydrogenationofPrimaryandSecondary AlcoholsCatalysedbyPhosphine-freeC,CChelatedIr(III) NHCComplexes
Description
Herein, an efficient, atom-economic, environmentally benign catalyticprotocolhasbeendevelopedforsynthesisingketones and aldehydes by acceptorless dehydrogenationof alcohols. Theprotocol employsC, Cchelated Ir (III)NHCcomplexes to promoteacceptorlessdehydrogenationofbothsecondaryand primaryalcohols. Notably, oxidationof primaryalcohol selec tivelyyields thecorrespondingaldehydewhere formingester byproducts is possible. Using C, C chelated Ir (III) NHC complexes (0.1mol%), andacatalyticamountofbase tBuONa (5mol%), severalaliphaticandaromaticaldehydesandketones including more challenging carbonyl compounds bearing heterocyclic ringswereobtained inmoderate tohighyields. Moreover, the protocol is also efficient for synthesising industrially important molecules like heliotropin and 3,4,5 trimethoxyacetophenone inmoderateyields. Remarkably, the catalytic systemallows the straightforward synthesis of the potentially bio-active compound cholest-4-en-3-one through acceptorless dehydrogenation followedby doublebond iso merisationunder thereactionconditions. Lowcatalyst loading, mild reactionconditions, highselectivity, short reaction time, andbroad-substratescopesareafewinterestingcharacteristics ofthecatalyticprotocoldescribedherein.