1,1-Diphenylethylene preparation

DiphenyhnethyUithium [881-42-5] can be prepared by the metalation reaction of butyUithium with diphenyknethane in addition, the adduct of butyUithium and 1,1-diphenylethylene is convenientiy prepared in either hydrocarbon or polar solvents such as THF as shown in equation 18. 

This reaction can also be utili2ed to prepare functionali2ed initiators by reaction of butyUithium with a substituted 1,1-diphenylethylene derivative. For example, polymers end functionali2ed with primary amine, tertiary amine, phenol, and bis(phenol) groups have been prepared in essentiaUy quantitative yield by using the reaction of butyUithium with the corresponding substituted (or protected) 1,1-diphenylethylene (87). 

In this case the ylide was not isolated but allowed to react with ben2ophenone to give, after hydrolysis with hydrochloric acid, 1,1-diphenylethylene, diphenylacetaldehyde, and triphenylarsine (160). An excellent method for preparing arsonium ylides involves the reaction between a stable dia2o compound and triphenylarsine in the presence of a copper catalyst such as bis(acetylacetonato)copper(II) (161). Rather than a dia2o compound, an iodonium yhde can be used again a copper catalyst is necessary for an optimum yield of product. An example of the use of a dia2o compound is shown in the formulation of triphenyl arsonium 2,3,4-triphenylcyclopentadienyLide [29629-32-17, C H As ... 

Shortly after, Doetschman and Hutchison reported the first example of a reactive carbene in the crystalline solid state, by preparing diphenylcarbene from diphenyldi-azomethane in mixed crystals with 1,1-diphenylethylene 84 (Scheme 7.23). When the mixed crystals were irradiated, carbene 85 was detected by electron paramagnetic resonance (EPR) and the disappearance of the signal was monitored to determine its kinetic behavior. Two reactions were shown to take place under topochemical... 

S-b-MM was prepared according to the published procedures (4-6). Molecular weights in the desired range and with narrow, unimodal distibutions were obtained without resorting to extensive monomer purification (ljL) or capping of the styrene block with diphenylethylene (4,5,7-10). The S-b-MM contained about 10 mol% MM, and was conveniently characterized by 1H NMR and IR spectroscopy. 

Diphenylcyclopropane has been prepared in 24% yield by the Simmons-Smith reaction,2 in 78% yield by treatment of 3,3-diphenylpropyltrimethylammonium iodide with sodium or potassium amide,3 in 61% yield by reaction of 1,1-diphenyl-ethylene with dimethylsulfonium methylide,4 and in unspecified yields from 1,1-diphenylethylene by reaction with diazomethane followed by pyrolysis of the resulting pyrazoline or by reaction with ethyl diazoacetate followed by distillation of the corresponding acid over calcium oxide.5... 

Phenylcinnamic acid has been prepared previously by a variety of methods, the best of which appear to be the dehydration of ethyl j3-hydroxy-/3,(3-diphenylpropionate by treatment with sodium acetate in acetic acid6 and the reaction of 1,1-diphenylethylene with oxalyl chloride.7... 

Dialkyl methyl phosphonate derivatives 37a-c of mannopyranosides may be prepared from cyclic sulfate 36 by reaction with the appropriate lithiated methylphosphonate, prepared by titration of the corresponding methyl-phosphonate with butyllithium in the presence of 1,1-diphenylethylene as indicator (Equation 4) <2002TL4017>. 

In addition to its interesting structure, the triethylsilylium-aromatic complex has proved useful in preparing other cations. Reaction with 1,1-diphenylethylene, for example, provided the cation 95, the first example of a persistent p-silyl substituted carbocation (i.e., where decomposition by loss of the silyl group did not occur). 

The transfer hydrogenation of a-keto- S -unsaturated esters, catalyzed by Ru(p-cymene)(TsDPEN) (TsDPEN monotosylated l,2-diphenylethylene-l,2-dia-mine) with 2-propanol as the hydrogen source, has been developed as an efficient method for the preparation of a-hydroxy-)S, y-unsaturated esters or acids. 

Another convenient method for the preparation of functionalized cyclobutanol derivatives is by treatment of 1,2-diphenylethylene acetals containing a 1,3-dithiane moiety in the y-position, e.g. 14c. with butyllithium. The isolation of 2,2-(propane-l,3-diyldisulfanyl)cyclobutanol (15c) together with benzyl phenyl ketone in 90 and 92 % yield, respectively, indicates that the reaction mechanism should involve the intramolecular attack of the metalated dithiane on the acetal carbon atom with concomitant hydride shift at the acetal group.15... 

In a paper edited in 1953, concerned with the preparation of the stereoisomeric forms of pentaphenylphosphorus, Wittig and GeiBler described the reaction of methylene-triphenylphosphorane 1 and benzophenone 2, forming 1,1-diphenylethylene 3 and triphenylphosphine oxide 4 (Scheme 1). Soon afterwards, it could be demonstrated that alkylidenephosphoranes (phosphine alkylenes, phosphorus ylides) generally react with carbonyl compounds such as aldehydes and ketones to give alkenes with the formation of phosphine oxide 1,2). 

A method for preparing polymers in a narrow molecular weight distribution by controlled radical polymerization in an aqueous solution using (3-cyclodextrin as the macroinitiator intermediate and 1,1 -diphenylethylene as the regulator is described. Since this method requires considerably lower amounts of both initiator and regulator, polymers contain limited amounts of regulator and initiator decomposition products. 

The preparation of other stereospecific hydrogenation catalysts such as ruthenium dichloride((S)-(6,6 -dimethoxybiphenyl-2,2 -diyl)bis[bis(3,5-dimethyl-xylene)((R,R)-2-diphenylethylene-diamine)] is provided (2). Other suitable ligands such as l,2-bis(2,5-dimethylphospholano)benzene are described (3). 

Dilithium reagents derived by reductive coupling of alkenes such as styrene and 1,1-diphenylethylene are important for the preparation of ring compounds (equation 7). 

Commercially, the best way to prepare 1,1-DPE is probably to react styrene and benzene with one another and then to dehydrogenate the resulting 1,1-diphenylethane to 1,1-diphenylethylene. This has been developed to the pilot plant stage in BASF [7]. 

On a laboratory scale, 1,1-diphenylethylene may be prepared using the Grignard reaction between phenylmagnesium bromide and acetophenone [6]. 

Simpler procedures are of course available for the preparation and characterisation of carbenium ions in solution, particularly for the more stable ones. Concentrated sulphuric acid was extensively used as protogenic medium before the superacid mixtures were shown to be superior, but many of the spectroscopic assignements in those earlier studies were later proved erroneous, particularly in the case of such reactive entities as the 1-phenylethylium ion Model monomers which cannot polymerise because of steric hindrance can generate fairly stable carbenium ions by interacting with Lewis or Br nsted acids in normal cationic polymerisation conditions. Thus, 1,1-diphenylethylene and its dimer, and 1,1-diphenylpropene give rise to typical visible absorption bands from which the concentration of the corresponding diphenyl-methylium ions can be accurately calculated. As for carbenium ions capable of forming stable salts, their synthesis and characterisation is obviously easy. 

If complexation between TiCl4 and the olefin (and with arcxnatic dimers and polymers) does take place to such a degree that the catalyst complexed is not available for initiation, as suggested by Sauvet et al. for 1,1-diphenylethylene, then obviously the inverse catalyst efficiency, expressed as the number of its molecules consumed to prepare one active species, will be higher tiian three, although again the stoicheiometiy of the initiation step remains simply one to one. 

Solution-phase studies are more important preparatively. Two main mechanisms seem to operate in solution. The first is attack of the radical cation of a heteroaromatic donor on a tz nucleophile, as happens in the arylation reactions reported above. Other examples include photochemical reactions in which the heterocycle participates as a donor—for example the formation of 2- and 3-(l,2-diphenylethyl)-pyrroles (yield 44 and 10 %, respectively) from the irradiation of ( )-stilbene in the presence of pyrrole, a reaction which evidence implies is initiated by SET from pyrrole [88]. 2-(2, 2 -Diphenylethyl)furans are cleanly formed on irradiation of the corresponding furans in the presence of 1,1-diphenylethylene and an electron-accepting sensitizer [89]. Likewise, irradiation of naphthalene and benzothiophene in the presence of pyrrole results in electron transfer from the latter and leads eventually to pyrrolyldihydronaphthalene or benzothiophene, 44, respectively (Scheme 29) [90]. 

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