Organometallic Bridge Diversification of Bicyclo[1.1.1]pentanes

Abstract

Bicyclo[1.1.1]pentane (BCP) derivatives have attracted significant recent interest in drug discovery as alkyne, tert‐butyl and arene bioisosteres, where their incorporation is frequently associated with increased compound solubility and metabolic stability. While strategies for functionalisation of the bridgehead (1,3) positions are extensively developed, platforms allowing divergent substitution at the bridge (2,4,5) positions remain limited. Recent reports have introduced 1‐electron strategies for arylation and incorporation of a small range of other substituents, but are limited in terms of scope, yields or practical complexity. Herein, we show the synthesis of diverse 1,2,3‐trifunctionalised BCPs through lithium‐halogen exchange of a readily accessible BCP bromide. When coupled with medicinally relevant product derivatisations, our developed 2‐electron “late stage” approach provides rapid and straightforward access to unprecedented BCP structural diversity (>20 hitherto‐unknown motifs reported). Additionally, we describe a method for the synthesis of enantioenriched “chiral‐at‐BCP” bicyclo[1.1.1]pentanes through a novel stereoselective bridgehead desymmetrisation.

(Bio)isosteres of ortho- and meta-substituted benzenes

“…The previously discussed C–H activation reported by MacMillan and co-workers ( Scheme 2 ) was used to access a wide number of 1,2,3-BCPs [ 33 ]. A wide variety of 1,2,3-BCPs bearing substituents in the bridge position were reported by Measom and co-workers in their study on the lithium–halogen exchange of 2-bromo-1,2,3-BCPs [ 78 ].…”