Recent Advances in Transition-Metal-Catalyzed C–H Functionalization Reactions Involving Aza/Oxabicyclic Alkenes

Abstract

Bicyclic alkenes, including Oxa- and azabicyclic alkenes can be readily activated by using transition-metal complexes with facial selectivity, because of the intrinsic angle strain on carbon-carbon double bonds of these unsymmetrical bicyclic systems. During last decades considerable progress has been done in the area of ring-opening of bicyclic strained ring by employing the concept of C-H activation. This Review comprehensively compiles the various C-H bond activation assisted reactions of oxa- and azabicyclic alkenes, viz., ring-opening reactions, hydroarylation as well as annulation reactions.

Insights into the Regioselectivity of Metal-Catalyzed Aryne Reactions

“…Evidently, there are a variety of steric and electronic factors that influence the regioselectivities of metal-mediated aryne reactions, but none have been extensively studied or used to the advantage of improving selectivity. 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 Prior to our initial disclosure, ligands had never been utilized to alter selectivity of aryne transformations, despite innumerable reports of ligand-controlled selectivity in other areas of organometallic chemistry (i.e., allylic substitution, Heck reactions, olefin metathesis). 49–57…”

Rhodium-Catalyzed Diastereoselective C–H Activation/[4 + 2] Annulation of α,β-Unsaturated Amides with Bicyclic Alkenes

“…Over the past two decades, direct C–H bond activation/annulation by transition-metal catalysis for the synthesis of heterocycles has drawn much attention and made tremendous progress. , In particular, due to the unique characteristics of heterobicyclic alkenes, such as a bridged oxygen/nitrogen atom, an alkene group, and a highly strained ring, heterobicyclic alkenes have been frequently used as versatile reaction partners in transition-metal-catalyzed C–H activation reactions (Scheme ). − …”

One-Pot Synthesis of Benzo[c]phenanthridine Alkaloids from 7-Azabenzonorbornadienes and Aryl Nitrones

“…In this context, nitrone is often used as a coupling partner and shows unique reactivity due to the electrophilicity of the imine moiety. − In this methodology, the nitrone moiety functions as a directing group as well as leaving group. Herein, we report a synthesis of novel benzophenanthridines via a cyclization reaction of aryl nitrones with 7-azabenzonorbornadienes. , The present protocol was compatible with various aromatic nitrones as well as azabicyclic alkenes and displayed wide functional group tolerance. Using this methodology, highly useful alkaloids such as O -methylnorfagaronine, norchelerythrine, decarine, norsanguinarine, and nornitidine were synthesized in a single step.…”