Transannular Functionalization of Multiple C(sp3)-H Bonds of Tropane via an Alkene-Bridged Palladium(I) Dimer.

This communication describes the Pd-catalyzed C(sp3)-H functionalization of a tropane derivative to generate products with functionalization at two (ß/γ) or three (ß/γ/ß) different sites on the alicyclic amine core. These reactions proceed via an initial dehydrogenation to generate an alkene product that can react further to form a Pd(I) alkene-bridged dimer. Functionalization of this dimer affords ß/γ/ß-functionalized allylic arylation and allylic acetoxylation products.

Regioselective Alkylative Cross-Coupling of Remote Unactivated C(sp3)-H Bonds.

The functionalization of unactivated C(sp3)-H bonds poses a significant challenge due to their ubiquity and relative similarity in most organic frameworks. Herein, we describe the use of a combined photoredox and nickel catalytic system for the regioselective C(sp3)-C(sp3) coupling of unactivated C(sp3)-H bonds and alkyl bromides. Positional selectivity is dictated by a 1,5-hydrogen atom transfer (HAT) reaction by a pendent amide. Interception of this radical by a Ni catalyst allows distal alkylation to occur in good yield and excellent selectivity.

A Mild Hydroaminoalkylation of Conjugated Dienes Using a Unified Cobalt and Photoredox Catalytic System.

Metallo-photoredox catalysis has redefined the available bond disconnections in the synthetic arsenal. By harnessing the one-electron chemistry of photoredox catalysis in tandem with low-valent cobalt catalysts, new methods by which functionalities may be stitched together become available. Herein we describe the coupling of photoredox-generated α-amino radical species with conjugated dienes using a unified cobalt and iridium catalytic system in order to access a variety of useful homoallylic amines from simple commercially available starting materials. We present a series of mechanistic experiments that support the intervention of Co-hydride intermediates that undergo diene insertion to generate Co-π-allyl species.

A Photochemical Two-Step Formal [5+2] Cycloaddition: A Condensation/Ring-Expansion Approach to Substituted Azepanes.

Seven-membered nitrogen-containing heterocycles are considerably underrepresented in the literature compared to their five- and six-membered analogues. Herein, we report a relatively understudied photochemical rearrangement of N-vinylpyrrolidinones to azepin-4-ones in good yields. This transformation allows for the conversion of readily available pyrrolidinones and aldehydes to densely functionalized azepane derivatives in a facile two step procedure.