Ring-Closing Metathesis Reactions of Acyloxysulfones: Synthesis of γ-Alkylidene Butenolides
An acyloxysulfone ring-closing metathesis/sulfone elimination sequence has been developed for the preparation of various γ-alkylidene butenolides. The elimination is proposed to proceed via an E1cb mechanism leading to (Z)-γ-alkylidene butenolides as the major products.
Phan, Iris T.,Gilbert, Garrett J.,O'Neil, Gregory W.
p. 1867 - 1871
(2015/08/06)
A Novel Access to γ-Alkylidenebutenolides: Sequential Stille Couplings of Dibromomethylenebutenolides
γ-(Dibromomethylene)butenolide (2) and β-bromo-γ- (bromomethylene)butenolide (Z-5), both of which obtained from dibromolevulinic acid (6) in a single step, underwent Pd-catalyzed couplings with phenyl- or styryltributylstannane giving mono-bromobutenolides with excellent stereo- and regiocontrol. A second Stille coupling or the reduction with Zn dust led to bromine-free γ-alkylidenebutenolides as single stereoisomers.
Sorg, Achim,Siegel, Konrad,Bru?ckner, Reinhard
p. 321 - 325
(2007/10/03)
THE SERIES OF SUBSTITUTED BUTANOLIDES AND BUTENOLIDES. IV. 4-ARYLIDENE(HETEROARYLIDENE)-2-BUTENOLIDES
A larger number of 4-arylidene- and 4-heteroarylidene-2-butenolides were obtained by the reaction of 2-butenolide with aromatic and heteroaromatic aldehydes in the presence of piperidine.
Cyclisation of Acetylenecarboxylic Acid. Synthesis of γ-Methylenebutyrolactones
Various γ-exo-methylenebutyrolactones have been synthesized in excellent yield by the cyclisation of acetylenecarboxylic acids in the presence of a catalytic amount of mercury(II) oxide.Cyclisation of terminal acetylene compounds proceeded regioselectively to give γ-exo-methylenebutyrolactones as the sole product.Disubstituted acetylenes also gave the (Z)-configurational enol lactone, but small amounts of an (E)-isomer of a γ-exo-enol lactone and a δ-lactone (α-pyrone) were also formed.Spectral properties and stereochemistry of the exo-enol lactones are also discussed.
Yamamato, Makoto
p. 582 - 587
(2007/10/02)
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