1191-24-8Relevant articles and documents
1,2-BIS (DIPHENYLPHOSPHINO)ETHANE TETRAHALIDE: A CONVENIENT REAGENT FOR THE CONVERSION OF ALCOHOLS TO THE CORRESPONDING HALIDES
Schmidt, Steven P.,Brooks, Dee W.
, p. 767 - 768 (1987)
Efficient and rapid conversion under mild conditions of various alcohols and tetrahydro-2-pyranyl (THP) protected alcohols into the corresponding halide (Br or I) are described using the corresponding 1,2-bis (triphenylphosphino)ethane tetrahalide.Tert-butyldimethylsilyl ethers, esters and olefins are stable to these conditions.
Catalytic phosphorus(V)-mediated nucleophilic substitution reactions: Development of a catalytic appel reaction
Denton, Ross M.,An, Jie,Adeniran, Beatrice,Blake, Alexander J.,Lewis, William,Poulton, Andrew M.
experimental part, p. 6749 - 6767 (2011/10/02)
Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.
Solvent and Counterion Effects on the Stereochemistry and the Competition between Electron-Transfer and SN2 Mechanisms in the Reaction of (Trimethylstannyl)alkalies with Bromides
Alnajjar, Mikhail S.,Kuivila, Henry G.
, p. 416 - 423 (2007/10/02)
Recations of (trimethylstannyl)alkalies (Me3SnM, M=Li, Na, K) with bromides have been studied in solvents including tetraglyme and tetrahydrofuran, in mixtures of tetrahydrofuran with ether and with benzene, and with added crown ether, 18-C-6.Product distributions and stereochemistry have been examined.Dicyclohexylphosphine (DCPH) was used as a trap for intermediate free radicals to detect participation of an electron-transfer (ET) process which occurs in competition with the SN2 mechanism.The effect of the nature of the cation on the course of the reaction depends upon the medium.The effects is not usually in simple relation to the size of the cation.The SN2 mechanism competes most effectively in a good coordinating medium but is not the exclusive one with 2-bromooctane even in THF containing 18-C-6.In the poorly coordinating mixed solvents, 2-bromooctane reacts virtually exclusively by an ET process.Even the primary 1-bromooctane and 6-bromo-1-hexene show ET contributions in the mixed solvents of low cation coordinating ability.In the latter case the ET component was established both by DCPH trapping experiments and by formation of the cyclic substitution product, (cyclopentylmethyl)trimethylstannane.The mechanistic implications of these and other observations are examined.
