Quadruple Role of Pd Catalyst in Domino Reaction Involving Aryl to Alkyl 1,5-Pd Migration to Access 1,9-Bridged Triptycenes

Rapid Access to Fused Tetracyclic N-Heterocycles via Amino-to-Alkyl 1,5-Palladium Migration Coupled with Intramolecular C(sp3)-C(sp2) Coupling

An unprecedented route for the preparation of fused tetracyclic N-heterocycles is presented through the palladium-catalyzed cyclization of isocyanides with alkyne-tethered aryl iodides. In this transformation, a novel amino-to-alkyl 1,5-palladium migration/intramolecular C(sp3)-C(sp2) coupling sequence was observed first. More importantly, isocyanide exhibited three roles, serving simultaneously as a C1 synthon, a C1N1 synthon, and the donor of C(sp3) for C(sp3)-C(sp2) coupling, and the reaction was the sole successful example that achieved C(sp3)-H activation of isocyanide.

Cycloaddition Initiated by Ynolates: High-Energy Dianion Equivalents as a Molecular Glue

In this paper, ynolate-initiated cycloaddition (annulation) to form a range of carbocycles and heterocycles is described. Ynolates consist of a ketene anion equivalent, which contains both nucleophilic and electrophilic moieties, and a carbodianion equivalent that achieves double addition. Hence, in addition to the usual [n+2] cycloaddition, ynolates can perform formal [n+1]-type annulations. Their high-energy performance has been demonstrated by their triple addition to arynes to generate triptycenes, in which the C–C triple bond of ynolates is cleaved. The synthetic applications of these methods, including natural products synthesis, are also described.

1 Introduction

2 Preparation of Ynolates

2.1 Double Lithiation

2.2 Flow Synthesis

2.3 Double Deprotonation

3 [2+2] Cycloaddition to C=O Bond

3.1 To Aldehydes and Ketones

3.2 Sequential Cycloaddition

4 [2+2] Cycloaddition to Imino Groups