The use of microwaveheatingtechnique for the acceleration of ortho ester Claisen rearrangement (a three step transformation) is described. Irradiation of a DMF solution of the allyl alcohol , triethyl orthoacetate and propionic acid (catalytic) in an Erlenmeyer flask for 10 minutes in a microwave oven generated the ester in 83% yield. Analogously, ortho ester Claisen rearrangement of a variety of
The claisen rearrangement in synthesis: acceleration of the johnson orthoester protocol en route to bicyclic lactones
作者:Graham B. Jones、Robert S. Huber、Sotheary Chau
DOI:10.1016/s0040-4020(01)80306-9
日期:1993.1
Catalysis of the Claisenorthoesterrearrangement of triethyl orthoacetate and a number of 2-cycloalken-1-ols has been achieved using acidic catalysis and brief microwavethermolysis in DMF. Unlike conventional methods of thermolysis, very high yields of rearranged products are typically obtained in less than ten minutes, and the Claisen products themselves require no further purification. The synthetic
Lithium–liquid ammonia mediated carbocyclisation of δ,ε-unsaturated esters: annulation of cyclopentanones
作者:A. Srikrishna、S.S.V. Ramasastry
DOI:10.1016/j.tetlet.2003.10.164
日期:2004.1
Lithium–liquid ammonia mediated carbanion cyclisation of δ,ε-unsaturated esters leading to cyclopentanes, fused as well as spiro, via annulation is described.
The reaction of cyclic γ,δ-epoxy esters with p-toluenesulfonic acid monohydrate is described. The reaction carried out in benzene or methylene chloride gave tosyloxy lactones as product. The ethoxy or methoxy lactones were obtained when ethanol or methanol were used as solvent. A mechanism of this lactonization is proposed.