quite scarce. We describe an extremely mild and selective method for either the propargylation or allenylation of carbonyl compounds catalyzed by the abundant, safe, and inexpensive metal titanium. These reactions can selectively provide homopropargylic alcohols from aldehydes and ketones or α‐hydroxy‐allenes from aldehydes. The mechanisms involved were also investigated.
CpTiCl<sub>2</sub>
, an Improved Titanocene(III) Catalyst in Organic Synthesis
作者:Esther Roldan-Molina、Natalia M. Padial、Luis Lezama、J. Enrique Oltra
DOI:10.1002/ejoc.201801120
日期:2018.11.25
CpTiCl2, an improved titanocene(III) single‐electron transfer catalyst, under mild conditions provides excellent yields of homoallylic and homopropargylic alcohols in Barbier‐type allylation and propargylation reactions. Moreover, in the presence of a BOX ligand, it was capable of catalyzingenantioselective intramolecular allylations and propargylations (cyclizations) of ketones.
A hydroxy-1-alkyne is reacted with a tin hydride compound, and the obtained (E,Z)-hydroxyvinylstannanes are separated to give the (E)-substance which is further converted to a vinylcopper complex shown by
followed by the conjugate addition reaction with an α, β-unsaturated cyclopentenone, and the deprotecting reaction is subsequently carried out to prepare a prostaglandin or an intermediate of prostaglandins easily, efficiently and industrially favorably.