Bruce E. Maryanoff

NMR rate study on the Wittig reaction of 2,2-dimethylpropanal and tributylbutylidenephosphorane

Abstract The fate of intermediate oxaphosphetanes in the reaction of t -BuCHO and Bu 3 PCHPr was monitored with time. Cis oxaphosphetane 1a was converted to trans oxaphosphetane 1b at −55 °C with k 3 = 1.5 ⊚ 10 −4 s −1 , and 1b was converted to Bu 3 PO and alkene 2b at −15 °C with k 6 = 2.7 ⊚ 10 −5 s −1 (t 1 2 = 7.0 h).

Highly stereocontrolled proton transfer in an enammonium-iminium rearrangement. Mechanism of the stereoselective deoxygenation of 6-aryl-6-hydroxy-1,2,3,5,6,10b-hexahydropyrrolo[2.1-a]isoquinolines with borane-thf in trifluoroacetic acid.

Abstract Either diastereomer of 2 or 10 is deoxygenated with BH 3 -THF/CF 3 CO 2 H to give mainly the trans product, 3b or 11b . The process involves a key enammonium-iminium rearrangement in which there is almost exclusive proton delivery from a single face.