Triphenylphosphine dihalides

II. Halides from Alcohols and Phenols by Triphenylphosphine Dihalide... 

Triphenylphosphine reacts with carbon tetrachloride14 or carbon tetrabromide15 in the absence of alcohols to form the corresponding triphenylphosphine dihalomethylene ylide and triphenylphosphine dihalide. 

Oxidation of thiochroman-4-ol to thiochroman-4-one can be achieved without competing Pummerer rearrangement using triphenylphosphine dihalides in DMSO (Equation 92) <2002TL8355>. This oxidation has also been achieved using polymer-bound periodinane (82% yield) <1999T6785> and 2-iodoxybenzoic acid is also effective (92%) <1995JOC7272>. 

Alkyl halides N,N -Carbonyldiimidazole. Dimethyl formamides. Trimethylsilylsilyl polyphosphate. Triphenylphosphine dihalides. Triphenylphosphine-Diethylazodicar-boxylate-Zinc halide. Vilsmeier reagent. 

Epoxides react with triphenylphosphine dihalides to give r/c-dihalides. Some of the reactions are depicted in Scheme 2, but the stereochemical features... 

Acid amide-triphenylphosphine dihalide adducts (4) have found wide application in organic synthesis. - Synthetic equivalents are adducts (5) from acid amides and triphenylphosphine/CCU, which are prepared in situ from the educts. - With these reagents the following transformations have been performed dehydration of amides or aldoximes to nitriles, preparation of isonitriles from secondary form-amides, preparation of imidoyl halides from amides or acylhydrazines and preparation of ketene imines from amides. Using polymer-supported triphenylphosphine the work-up procedure is much easier to achieve. Triphenylphosphine can be replaced by tris(dialkylamino)phosphines. - Instead of CCI4 hexa-chloroethane, hexabromoethane or l,l,2,2-tetrabromo-l,2-dichloroethane can be used " the adducts thus formed are assumed to be more effective than those from the triphenylphosphine/CCU system. 

Uses of Phosphoranes in Organic Synthesis.— Triphenylphosphine dihalides (107) have been used to achieve cis-trans isomerization of simple alkenes, as shown in Scheme 9. The key to the sequence is that epoxides undergo a net c/j-addition of halogen on... 

ISOMERIZATION, ALKENES Polyphosphotic acid. Sodium iodide-Dimethyl-formamide. Triphenylphosphine dihalides. 

Triphcnylphosphinc-4)icthyl azodicai-boxyUte, 404-406 Ttiphenylphosphine-Iodine, 407 Triphenylphosphine dihalides, 407 Ttiphenylphosphite ozonide, 408... 

Olefin inversion via epoxides is reported by two groups of workers. One sequence involves epoxidation with peracid, which occurs with retention of stereochemistry, followed by deoxygenation with hexamethyldisilane and potassium methoxide in HMPT at 65 °C. The alternative procedure utilizes reaction of the episode with triphenylphosphine dihalides to give vicinal dihalides. Zinc reduction of the dihalides is specifically trans, and thus the sequence epoxidation-bromination-reduction gives overall inversion of olefin configuration. ... 

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