RESUMO
A catalytic enantioselective synthesis of the antimelanoma marine natural product (-)-palmerolide A was accomplished using a longest sequence of 21 steps and without resorting to stoichiometric chiral auxiliaries or the chiral pool. The right half was constructed with a new variant of the Claisen-Ireland rearrangement exploiting an alkenylboronate as a masked hydroxyl. The left half featured the first application of a diol.SnCl(4)-catalyzed enantioselective crotylboration in the context of a complex target. This distinct strategy could pave the way to the design of simplified analogues of palmerolide.
Assuntos
Compostos de Boro/química , Macrolídeos/síntese química , Catálise , Macrolídeos/química , EstereoisomerismoRESUMO
Titanium-catalyzed intermolecular hydroaminations of (E/Z)-chloroenynes enabled an efficient pyrrole synthesis, which set the stage for the development of a user-friendly one-pot reaction for the regioselective preparation of fully substituted pyrroles from easily accessible alpha-haloalkynols.
Assuntos
Alcinos/química , Hidrocarbonetos Clorados/química , Pirróis/síntese química , Titânio/química , Catálise , Técnicas de Química Combinatória , Estrutura Molecular , Pirróis/química , EstereoisomerismoRESUMO
An efficient methodology for the indirect anti-Markovnikov hydration of unsymmetrically substituted terminal and internal alkynes is based on TiCl4-catalyzed hydroamination reactions. Its application to ortho-alkynylhaloarenes, followed by a copper-catalyzed O-arylation, provides flexible access to substituted benzo[b]furans.
RESUMO
Two distinct economical catalysts for intramolecular hydroaminations of electronically unactivated alkenes with basic amines are described, which are based on (a) group 4 metal halides under basic reaction conditions or (b) Brønsted-acid organocatalysts.
Assuntos
Ácidos/química , Alcenos/química , Aminas/química , Compostos Heterocíclicos/síntese química , Aminação , Catálise , Cloretos/química , Ciclização , Háfnio/química , Compostos Heterocíclicos/química , Estrutura Molecular , Titânio/química , Zircônio/químicaRESUMO
A one-pot indole synthesis consisting of a highly regioselective TiCl(4)-catalyzed hydroamination and a 5-endo Heck cyclization starting from 2-chloroaniline is described, using an in-situ generated, sterically hindered imidazol-2-ylidene palladium complex.
RESUMO
[reaction: see text] An intermolecular hydroamination reaction of norbornene is presented that uses catalytic amounts of user-friendly TiCl(4) and tolerates a variety of functional groups. In addition, a secondary amine is converted using this methodology.