Dehydrodimerization of Heteroarylated Alkanes by Way of Organocopper Compounds

Scope and mechanism of direct indole and pyrrole couplings adjacent to carbonyl compounds: total synthesis of acremoauxin A and oxazinin 3

Full details are provided for a recently invented method to couple indoles and pyrroles to carbonyl compounds. The reaction is ideally suited for structurally complex substrates and exhibits high levels of chemoselectivity (functional group tolerability), regioselectivity (coupling occurs exclusively at C-3 of indole or C-2 of pyrrole), stereoselectivity (substrate control), and practicality (amenable to scaleup). In addition, quaternary stereocenters are easily and predictably generated. The reaction has been applied to a number of synthetic problems including total syntheses of members of the hapalindole family of natural products, ketorolac, acremoauxin A, and oxazinin 3. Mechanistically, this coupling protocol appears to operate by a single electron-transfer process requiring generation of an electron-deficient radical adjacent to a carbonyl which is then intercepted by an indole or pyrrole anion.

Design and synthesis of tridentate facially chelating ligands of the [2.n.1]-(2,6)-pyridinophane family

Syntheses are reported for tripyridine macrocycles 2 and 3 and some of their alkyl derivatives. The macrocycles are designed to stabilize to various extents coordinated d(8) metal precursors and d(6) alkane oxidative addition products (Pt(IV)), therefore allowing favorable kinetics and thermodynamics of (e.g., Pt(II)) the cleavage of substrate H-C(sp(3)) bonds. Both the Chichibabin protocol and oxidative coupling of carbanions by copper(I) iodide were used for the macrocyclization step. Crystal structures of singly and doubly protonated 2 establish atom connectivity in the macrocycle, and reveal structural features which are obscured in solution NMR by rapid proton migration.