Cobalt-catalyzed arylzincation of alkynes and alkenes involving 1,4-cobalt migration
Tan, Boon Hong
Date of Issue2014
School of Physical and Mathematical Sciences
Development in the fields of organometallic chemistry and homogenous catalysis enable synthetic chemists to utilize seemingly unreactive C–H bonds synthetic handle for various transformations to access more complex organic molecules. Metal migrations via C-H bond activation, 1,4-migrations in particular, have attracted interest not only as a mechanistically intriguing organometallic elementary process but also as an entry channel to novel C-H bond functionalization and cascade bond-forming reactions. This thesis describes the development of cobalt-based catalyst for C–H bond functionalization reactions via 1,4-migration. First part of the thesis details the development of cobalt–Xantphos complex catalyzed addition of an arylzinc reagent to an alkyne to afford ortho-alkenylarylzinc species via vinyl-to-aryl 1,4-cobalt migration. Further synthetic manipulations of ortho-alkenylarylzinc species allow the access to various benzo-fused carbocycles. Second part of the thesis describes a cobalt-catalyzed migratory arylzincation reaction of norbornene derivatives, which is distinct from the rhodium-catalyzed "merry-go-round" addition of an arylboronic acid to norbornene. Thus, a cobalt–dppf complex catalyzes the addition of an arylzinc reagent to a norbornene derivative to afford an ortho-norbornylarylzinc species under mild conditions, which can be intercepted by common organic electrophiles under copper or palladium catalysis under one-pot condition.
DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis