Stereoselective Halo-Succinimide Facilitated α-Halogenations of Substituted α-Trialkylsilyl-β-Substituted-α,β-Unsaturated Esters
The NXS (X = Cl, Br)-mediated halogenation of a series of (E)-α-trimethylsilyl-β-alkyl(aryl)-α,β-unsaturated esters in dimethylformamide (DMF) has furnished (Z)-β-substituted-α-halogenated-α,β-unsaturated ester products in moderate to high isolated yields (58-90%) with dr values of >20:1 coupled with the inversion of olefin stereochemistry. The reaction process was hypothesized to include an initial halonium cation intermediate, followed by regioselective ring opening with DMF. Subsequentanti-E2-type concomitant elimination allowed for the stereoselective formation of the product vinylic bromo-and chloroesters.
Jennings, Michael P.,Probasco, Kristina C.
p. 8945 - 8954
(2021/07/20)
Chemo- and stereoselectivity of the reaction of aromatic aldehydes with triphenylphosphine and trichloroacetic acid derivatives
Aromatic aldehydes react with triphenylphosphine and ethyl trichloroacetate or trichloroacetonitrile to give the corresponding benzylidene dichlorides or α-chlorocinnamic acid derivatives. The chemo- and regioselectivity of these reactions depend on both the substituent in the aromatic ring and reaction conditions. The product configuration was determined on the basis of the coupling constants 2JCH and 3JCH in the 13C NMR spectra. Pleiades Publishing, Inc., 2006.
Matveeva,Erin,Osetrov,Leshcheva,Kurts
p. 388 - 392
(2007/10/03)
A convenient halogenation of α,β-unsaturated carbonyl compounds with OXONE and hydrohalic acid (HBr,HCl)
Mixtures of OXONE and hydrobromic acid or hydrochloric acid afford solutions of bromine or chlorine, respectively, α-Bromo- or α-chloro-α,β-unsaturated carbonyl compounds were prepared by addition of hydrobromic acid or hydrochloric acid to the mixture of
Kim, Kyoung-Mahn,Park, In-Hwan
p. 2641 - 2644
(2007/10/03)
α-hypervalent iodine functionalized phosphonium and arsonium ylides and their tandem reaction as umpolung reagents
α-Hypervalent iodine functionalized phosphonium and arsonium ylides 2 can be used as umpolung ylides to react with nucleophiles to give α-heteroatom substituted ylides 4 in good yields. The nucleophilic substitution - Wittig tandem reaction of 2 can occur smoothly to provide an efficient method for the synthesis of (Z)-α-halo-α,β-unsaturated enoates or enones 6, stereoselectively.
Huang, Zhizhen,Yu, Xiaochun,Huang, Xian
p. 8261 - 8264
(2007/10/03)
Efficient electrosynthesis of α-chloro-α,β-unsaturated carboxylic and phosphonic esters using magnesium electrochemical activation
Various α-chloro-α,β-unsaturated carboxylic or phosphonic esters were easily and rapidly prepared under mild conditions in DMF, by electrolysing respectively triethyl dichloromethylphosphonoacetate and tetraethyl dichloromethyl-bis-phosphonate, then treat