Selective Metal‐free HB(C₆F₅)₂ Catalyzed Allene Cyclotrimerization: Formation of 1,3,5‐Trimethylenecyclohexane and Its Tris‐hydroboration Product

Abstract

Allene is cyclotrimerized under metal‐free conditions with the borane HB(C6F5)2 catalyst to selectively give 1,3,5‐trimethylenecyclohexane (3 a). Three‐fold hydroboration of the 1,3,5‐cyclotrimer with Piers’ borane gives the all‐cis 1,3,5‐CH2B(C6F5)2 substituted cyclohexane product 14.

Borane‐Induced Dimerization of Arylallenes

“…[6] Thea nalogous reaction of cyclohexylallene (4a)l ed to the trans,cis-tricyclohexyl-substituted 1,3,5-trimethylenecyclohexane 5a. [5] We have now found as econd closely related example,namely the HB(C 6 F 5 ) 2 -catalyzed cyclotrimerization of n-octylallene (4b)t ogive the cyclotrimer 5b as the major product (see the Supporting Information for details).…”

“…[2,3] Stoichiometric syntheses of 2 have been reported. [4] We reported [5] that the selective cyclotrimerization of 1 to give 2 is catalyzed by the borane HB(C 6 F 5 ) 2 (3;S cheme 1). [6] Thea nalogous reaction of cyclohexylallene (4a)l ed to the trans,cis-tricyclohexyl-substituted 1,3,5-trimethylenecyclohexane 5a.…”