Stereoselective transition metal-catalysed higher-order carbocyclisation reactions

Abstract

Transition metal-catalysed higher-order carbocyclisation reactions represent an important class of reactions due to their ability to construct complex polycyclic systems in a highly selective and atom-economical fashion. A key and striking feature with these transformations is the dichotomy in reactivity that a substrate displays with different transition metal complexes, which is akin to the manner enzymes direct terpene biosynthesis. This tutorial review details the historical development of higher-order carbocyclisation reactions, specifically the variants of [m+2+2] that involve carbon-based pi-systems, where m = 2, 3 and 4, in the context of critical developments with various transition metal complexes.

Alkynes as Electrophilic or Nucleophilic Allylmetal Precursors in Transition‐Metal Catalysis

“…[16a] A broad range of alkyl-substituted terminal alkynes react efficiently with various aliphatic, aromatic and α,β-unsaturated carboxylic acids to form the branched allylic esters as single regioisomers. Such branched regioselectivity, which also is evident in conventional rhodium-catalyzed allylic substitutions [24] and related allene hydrofunctionalizations, [5] complements the linear regioselectivity observed in corresponding palladium catalyzed reactions. This transformation proved very sensitive to the nature of the ligand.…”

Gold(I)-catalyzed enantioselective cycloaddition reactions

“…Moreover, cycloadditions are atom economical, and usually take place with high levels of regio- and stereocontrol. Especially relevant in terms of synthetic practicality are cycloadditions which are catalyzed by transition metal complexes [19–23]. In particular, gold(I) complexes, owing to their high carbophilicity, low oxophilicity and high oxidation potential between gold(I) and gold(III) have shown a unique potential to unveil novel types of chemoselective and stereoselective cycloadditions involving alkynes, allenes or alkenes [24–26].…”

Rhodium‐Catalyzed [(3+2)+2] Carbocyclization of Alkynylidenecyclopropanes with Substituted Allenes: Stereoselective Construction of Tri‐ and Tetrasubstituted Exocyclic Olefins

“…To this end, metalcatalyzed higher-order cycloaddition reactions provide a powerful and versatile approach for the construction of carbo-and heterocyclic systems through the combination of relatively simple building blocks, namely alkynes and alkenes. [1,2] …”

“…In addition, monosubstituted allenes are either unreactive or provide proximal insertion, thereby making this a challenging problem. [10][11][12][13] Herein, we describe the first regio-and stereoselective rhodium-catalyzed [(3+2)+2] carbocyclization of carbon-and heteroatom tethered ACPs (1) with activated and unactivated exogenous allenes (2) to afford the bicycloheptatrienes 3 with tri-and tetrasubstituted exocyclic olefins (Scheme 1 c). Additionally, this process provides a rare example of a highly selective distal carbometalation of a mono-or 1,1-disubstituted allene in a metalcatalyzed cycloaddition reaction.…”