Alkenes from β-lithiooxyphosphonium ylides generated by trapping α-lithiated terminal epoxides with triphenylphosphine
作者:David M Hodgson、Rosanne S D Persaud
DOI:10.3762/bjoc.8.219
日期:——
Terminal epoxides undergo lithium 2,2,6,6-tetramethylpiperidide-induced alpha-lithiation and subsequent interception with Ph(3)P to provide a new and direct entry to beta-lithiooxyphosphonium ylides. The intermediacy of such an ylide is demonstrated by representative alkene-forming reactions with chloromethyl pivalate, benzaldehyde and CD(3)OD, giving a Z-allylic pivalate, a conjugated E-allylic alcohol
Hydrogallation of carbon-carbon multiple bonds proceeds in the presence of triethylborane as a radical initiator. Several functionalities do not interfere with this reaction. Resulting alkenyl- and alkylgallium species can be trapped by several electrophiles. Highly regioselective radical addition of an indium hydride reagent to alkynes is also achieved. Various functionalities are tolerant under the reaction conditions. The reaction proceeds with complete anti stereoselectivity. Alkenylindiums obtained via hydroindation can be employed for the following cross-coupling reaction with aryl halides in one pot.