Synthesis and steric structure of 3′,3′,5′-trimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]trioxa[1λ5]phosphabicyclo[3.2.1]octane] and 3′,5′-dimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]trioxa[1λ5]phosphabicyclo[3.2.1]oct[3]ene]

Reactions of hexafluoroacetone with 4-(1,3,2-benzodioxaphosphol-2-yloxy)-4-methylpentan-2-one and 4-(1,3,2-benzodioxaphosphol-2-yloxy)pent-3-en-2-one afforded cage spiro phosphoranes with a phosphorus-carbon bond, 3′,3′,5′-trimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]-trioxa[1λ5]phosphabicyclo[3.2.1]octane] and 3′,5′-dimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]trioxa[1λ5]phosphabicyclo[3.2.1]oct[3]ene], whose structure was determined by X-ray analysis.