Stereoselective PCO/POC Rearrangement of P C Cage Phosphorane in the Reaction of 4,5 Dimethyl 2 (2 oxo 1,2 diphenyl)ethoxy 1,3,2 dioxaphospholane with Hexafluoroacetone.
Interaction of 4,5 dimethyl 2 (2 oxo 1,2 diphenyl)ethoxy 1,3,2 dioxaphospholane, bearing a carboxyl group in the g position with respect to the phosphorus atom and obtained from d,l butanediol, with hexafluoroacetone (CCl4, 40 degC) leads to the simultaneous formation of regio and stereoisomeric cage like phosphoranes with phosphorus carbon and phosphorus oxygen bonds with a high stereoselectivity >95% whose structure was determined by 1D and 2D NMR spectroscopy and XRD. When stored as a solution in dichloromethane for one month, the PCO isomer rearranges into the thermodynamically more stable POC isomer of the cage like phosphorane. Mild hydrolysis of the PCO/POC isomers proceeds with a high chemoselectivity and leads to the formation of P(IV) dioxaphospholane derivatives. Acidic hydrolysis of the POC isomer leads to the formation of an oxirane derivative with an unexpectedly high stereoselectivity >95% DFT calculations (using the PBE functional) allowed us to obtain structures and energies of the initial phospholane, reaction products (PCO/POC isomers) and an intermediate P(V) oxaphosphirane.
The Journal of organic chemistry