- Iron(II)/copper(I)-mediated stereoselective carbozincation of ynamides. One-pot synthesis of α-allyl-tetrasubstituted-enamides
-
The iron(II) chloride- and copper(I) iodide-mediated carbozincation of a panel of substituted ynamides is described in this article. The reaction is totally regio- and stereoselective. Experiments showed that the reaction mediated with Fe(II) was more substrate dependent than the reaction performed with Cu(I). Interestingly, in the presence of allylbromide, stereoselective carboallylation can be achieved for the first time in a one-pot procedure, leading to skipped dienamides.
- Lingua, Hugo,Vibert, Fran?ois,Mouysset, Dominique,Siri, Didier,Bertrand, Michèle P.,Feray, Laurence
-
p. 3415 - 3422
(2017/06/01)
-
- Cu-Catalyzed Alkylative Carboxylation of Ynamides with Dialkylzinc Reagents and Carbon Dioxide
-
Alkylative carboxylation of ynamides with CO2 and dialkylzinc reagents using a N-heterocyclic carbene (NHC)-copper catalyst has been developed. A variety of ynamides, both cyclic and acyclic, undergo this transformation under mild conditions to afford the corresponding α,β-unsaturated carboxylic acids, which contain the α,β-dehydroamino acid skeleton. The present alkylative carboxylation formally consists of Cu-catalyzed carbozincation of ynamides with dialkylzinc reagents with the subsequent nucleophilic carboxylation of the resulting alkenylzinc species with CO2. Dialkylzinc reagents bearing a β-hydrogen atom such as Et2Zn and Bu2Zn still afford the alkylated products despite the potential for β-hydride elimination. This protocol would be a desirable method for the synthesis of highly substituted α,β- dehydroamino acid derivatives due to its high regio- and stereoselectivity, simple one-pot procedure, and its use of CO2 as a starting material. CO2 incorporation with alkylation: Alkylative carboxylation of ynamides with CO2 and a dialkylzinc reagent has been achieved by using a N-heterocyclic carbene (NHC)-copper complex as the catalyst. The reactions proceeded by Cu-catalyzed carbozincation of ynamides with dialkylzinc reagents and the subsequent carboxylation of the resulting alkenylzinc species (see scheme).
- Takimoto, Masanori,Gholap, Sandeep Suryabhan,Hou, Zhaomin
-
p. 15218 - 15223
(2015/11/02)
-
- Enecarbamates as Selective Substrates in Oxidations: Chiral-Auxiliary-Controlled Mode Selectivity and Diastereoselectivity in the [2+2] Cycloaddition and Ene Reaction of Singlet Oxygen and in the Epoxidation by DMD and mCPBA
-
The stereochemical course of the oxidation of chiral oxazolidinone-substituted enecarbamates has been studied for singlet oxygen (1O2), dimethyldioxirane (DMD), and m-chloroperbenzoic acid (mCPBA) by examining of the special structural and stereoelectronic features of the enecarbamates. Valuable mechanistic insight into these selective oxidations is gained. Whereas the R1 substituent on the chiral auxiliary is responsible for the steric shielding of the double bond and determines the sense of the π-facial diastereoselectivity, structural characteristic such as the Z/E configuration and the nature of the R 2 group on the double bond are responsible for the extent of the diastereoselectivity. Stereoelectronic steering by the vinylic nitrogen functionality controls the mode selectivity (ene reaction vs [2+2] cycloaddition) in the case of 1O2.
- Adam, Waldemar,Bosio, Sara G.,Turro, Nicholas J.,Wolff, Barbara T.
-
p. 1704 - 1715
(2007/10/03)
-
- Control of the mode selectivity (ene reaction versus [2 + 2] cycloaddition) in the photooxygenation of ene carbamates: Directing effect of an alkenylic nitrogen functionality
-
The geometry of the double bond in oxazolidinone-substituted ene carbamates controls the mode selectivity (ene reaction versus [2+2] cycloaddition) of singlet oxygen through stereoelectronic effects, whereas the chiral auxiliary provides high diastereoselectivity through steric shielding. Copyright
- Adam, Waldemar,Bosio, Sara G.,Turro, Nicholas J.
-
p. 14004 - 14005
(2007/10/03)
-