Highly efficient Ni- and Fe-catalyzed borylative cyclizations of enynes

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Orgánica. Fecha de lectura: 25-10-2019Esta tesis tiene embargado el acceso al texto completo hasta el 25-04-202

Brønsted acid−catalyzed synthesis of tetrasubstituted allenes and polysubstituted 2H-chromenes from tertiary propargylic alcohols

A practical and environmentally benign Brønsted acid−catalyzed protocol for the preparation of all-carbon tetrasubstituted allenes, consisting in the direct SNˈ addition of tri- or dimethoxy arenes or allyltrimethylsilane to tertiary propargylic alcohols, has been developed. In addition, a straightforward synthesis of densely substituted 2H-chromenes by metal-free tandem allenylation/heterocyclization reaction of methoxyphenols and tertiary alkynols is presented.Junta de Castilla y León and FEDER (BU291P18) and Ministerio de Economía y Competitividad (MINECO) and FEDER (CTQ2016-75023-C2-1-P

Atom-economical regioselective Ni-catalyzed hydroborylative cyclization of enynes: Development and mechanism

We report a full study on the novel regioselective Ni-catalyzed hydroborylative cyclization of enynes using HBpin as the borylation agent. Alkyl and alkenyl boronates can be obtained depending on the substituent on the alkyne. The reaction takes place under smooth conditions with an inexpensive catalytic Ni-based system, constituting a fully atom-economic eco-friendly method. This process shows a broad scope, allowing the formation of carbo- and heterocycles in moderate to good yields. The utility of the resulting boronates is also illustrated. We have studied the reaction mechanism both experimentally and computationally. The process involves initial oxidative cyclometalation to Ni(0)(xantphos) species followed by the key C-B bond formation through σ-bond metathesis and reductive eliminationWe thank the Spanish MINECO for funding (Grant CTQ2016-79826-R) and a Juan de la Cierva fellowship to M. T. Q., the MECD for a FPU fellowship to N. C.-L., and the Centro de Computación Científica-UA