- Pd0-Catalyzed carbonylation of 1,1-dichloro-1-alkenes, a new selective access to Z-α-chloroacrylates
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A novel and fully chemo- and stereoselective three component strategy leading to Z-α-chloroacrylates by a Pd0-catalyzed reaction of CO (1 atm) with 1,1-dichloro-1-alkenes and various alcohols is disclosed. This catalytic approach compares favourably with the Wittig type strategies as α-chloroacrylates of pure Z configuration are obtained in high yield. The Royal Society of Chemistry.
- Arthuis, Martin,Lecup, Anne,Roulland, Emmanuel
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supporting information; experimental part
p. 7810 - 7812
(2010/11/18)
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- Stereoselective olefination reactions promoted by Rieke manganese
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A study of the advantages of using manganese, an inexpensive and nontoxic metal, to perform stereoselective β-elimination reactions and to promote sequential olefination reactions of aldehydes to obtain α,β- unsaturated esters and amides is presented. Various elimination reactions, all of them characterized by occurring with complete stereoselectivity and in high yields, were performed using active manganese (Mn*) as metalating agent. This ability of manganese has been applied to develop a novel and direct synthesis of (E)-α,β-unsaturated esters or amides and (Z)-α,β-unsaturated α-halo esters and α-choroamides through a Mn*-mediated sequential olefination protocol of aldehydes with dichloro esters or amides and trihalo esters or trichloroamides, respectively. Georg Thieme Verlag Stuttgart.
- Concellon, Jose M.,Rodriguez-Solla, Humberto,Del Amo, Vicente,Diaz, Pamela
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experimental part
p. 2634 - 2645
(2009/12/06)
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- Stereoselective synthesis of (Z)-α-haloacrylic acid derivatives, and (Z)-haloallylic alcohols from aldehydes and trihaloesters or amides promoted by Rieke manganese
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A Mn*-promoted sequential process directed toward the synthesis of (Z)-α-halo-α,β-unsaturated esters or amides is described. In both cases, the process takes place with complete Z-stereoselectivity. In addition, (Z)-α-chloro-α,β-unsaturated ketones and carboxylic acids, and (Z)-haloallylic alcohols were readily prepared from (Z)-α-halo-α,β-unsaturated amides derived from morpholine, or esters. A mechanism has been proposed to explain the sequential process and the stereoselectivity observed. The Royal Society of Chemistry.
- Concellon, Jose M.,Rodriguez-Solla, Humberto,Diaz, Pamela
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experimental part
p. 2934 - 2940
(2009/02/02)
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- One-pot process in phosphonium-iodonium ylides: Nucleophilic substitution and the Wittig reaction
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The nucleophilic substitution in mixed phosphonium-iodonium ylides was investigated. The iodonium group is replaced by such S-containing nucleophiles as the thiocyanate anion or thiourea, as well as by halide ions. The structure of the reaction product with the thiocyanate ion was established by X-ray diffraction. A one-pot process involving the nucleophilic substitution and the Wittig reaction was developed.
- Matveeva,Podrugina,Pavlova,Mironov,Zefirov
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experimental part
p. 400 - 405
(2009/06/05)
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- Stereoselective preparation of (E)-α-bromoacrylates from mixtures of brominated ando phosphonates
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We prepared 69:31-11:89 mixtures of phosphonates 6b and 7b containing two phenoxy substituents, a CO2Et group, and 1 or 2 bromine atoms, respectively, at the interspersed methylene group. Deprotonating 64:36 mixtures of these reagents with NaH
- Olpp, Thomas,Brueckner, Reinhard
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p. 2135 - 2152
(2007/10/03)
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- Efficient electrosynthesis of α-chloro-α,β-unsaturated carboxylic and phosphonic esters using magnesium electrochemical activation
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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
- Goumain, Sophic,Jubault, Philippe,Feasson, Christian,Collignon, No?l
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p. 981 - 984
(2007/10/03)
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- Carbanions phosphonate prepares par voie electrochimique: formation et reactivite vis-a-vis d'un aldehyde
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Reactivity towards p-methoxybenzaldehyde (ArCHO) of electrochemically generated phosphonate carbanions has been investigated.Electrolyses were carried out at a mercury cathode in DMF and two routes to the desired carbanion have been compared: (i) Deprotonation of phosphonates of general formula (EtO)2P(O)CHYW (Y = W = Cl; Y = H, W = Cl; Y = Cl, W = CO2Et; Y = H, W = CO2Et; Y = CH3, W = CO2Et; Y = Cl, W = CH3), by the bases resulting from the electroreduction of azobenzene; addition of the carbanion formed onto the carbonyl group takes place and leads to the adduct (EtO)2P(O)CYW(Ar)O-. (ii) Two-electron reduction of halophosphonates (EtO)2P(O)CXYW (X = Cl, Y and W as above; X = Br, W = CO2Et, Y = Cl, Br, or CH3); when no H atom is present on the carbon bearing the phosphonate group (Y and W no = H), the same evolution leading to the above adduct is observed, on the contrary, when Y = H, the electrogenerated carbanion deprotonates the substrate and the resulting carbanion (EtO)2P(O)CXW reacts with the aldehyde; giving the adduct (EtO)2P(O)CXW(Ar)O-.Evolution of the intermediate adduct depends on the substituents Y (or X) and W: when W = CO2Et, whatever the nature of Y (or X), diethyl phosphate is eliminated with formation of the ethylenic ArCH=CWY (or X) (Wittig-Horner reaction); the same evolution is observed when Y = W = Cl.When W = Cl and Y = H or CH3, the final product is the phosphonate epoxyde resulting from chloride elimination (Darzens reaction).Chemo- and stereoselectivity depend only on the nature of Y and W but are independent of the mode of generation of the carbanion.Yields are limited by side-protonation reactions, which are related to the basicity of the phosphonate carbanions.Analysis of the results permits selection of the optimal electrolysis conditions for purposes of synthesis.Key words: electrosynthesis, electrogenerated bases, phosphonates, Wittig-Horner.
- Le Menn, Jean-Christophe,Sarrazin, Jean,Tallec, Andre
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p. 1332 - 1343
(2007/10/02)
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