1.1- Diphenylethylene, reaction with

Diphenylcyclopropenone, 47, 62 Dii henyldiacetylene, 45, 39 Diphenyl disulfide, oxidation to methyl benzenesulfinate, 46, 62 1,1-Diphenylethylene, reaction with N,or diphenylmtrone, 46,129 N,N -Diphi iiyli tiiyleni diamine, condensation with triethyl orthoformate, 47, 14... 

The necessary vicinal dihalides are themselves readily available by addition of Br2 or Cl2 to alkenes. Thus, the overall halogenation/dehvdrohalogenation sequence makes it possible to go from an alkene to an alkyne. for example, diphenylethylene is converted into diphenylacetylene by reaction with Br2 and subsequent base treatment. 

For some of these reactions detailed mechanistic studies were carried out. As an example, in Scheme 5 the pathway suggested for 1.1-diphenylethylene oxidation with O2 into benzophenon [23] is shown. 

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... 

Already, at an early stage of the studies on the captodative effect, Viehe s group (Lahousse et ai, 1984) measured relative rates for the addition of t-butoxyl radicals to 4,4 -disubstituted 1,1-diphenylethylenes and to substituted styrenes. This study did not reveal a special character of captodative-substituted olefins in such reactions. It might be that the stability of the radical to be formed does not influence the early transition state of the addition step. The rationalization of the kinetic studies mentioned above in terms of the FMO model indicates, indeed, an early transition state for these reactions, with the consequence that product properties should not influence the reactivity noticeably. 

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 structure-reactivity behavior found for similar organosodium polymerization initiators of styrene [27] or that for addition reactions with 1,1-diphenylethylene [28] is almost identical with that found for the lithium initiators of Table 3.1. It is interesting to note from Table 3.1 that the reactivity of lithium... 

This has been studied much less frequently and appears to be a rather more complex reaction. The first results obtained, for the butyl-lithium, styrene reaction in benzene have already been described. In a similar way the addition of butyllithium to 1,1-diphenylethylene shows identical kinetic behaviour in benzene (26). Even the proton extraction reaction with fluorene shows the typical one-sixth order in butyllithium (27). It appears therefore that in benzene solution at least, lithium alkyls react via a small equilibrium concentration of unassociated alkyl. This will of course not be true for reactions with polar molecules for reasons which will be apparent later. No definite information can be obtained on the dissociation process. It is possible that the hexamer dissociates completely on removal of one molecule or that a whole series of penta-mers, tetramers etc. exist in equilibrium. As long as equilibrium is maintained, the hexamer is the major species present and only monomeric butyllithium is reactive, the reaction order will be one-sixth. A plausible... 

Scission of the cyclopropane rr-bond is also observed in the intermediate cyclopropyl-methyl dilithio derivative obtained from 2-cyclopropyl-1,1-diphenylethylene upon reaction with lithium metal affording the open-chain dilithio-diphenylpentenyl salt (equation 41)91. Again, no experimental evidence for the presence of such intermediate was found though the analogous dilithioalkyne derivative was observed (see below)91. 

To overcome the difficulty in the crossover step a general methodology has been developed in our laboratory for the synthesis of block copolymers when the second monomer is more reactive than the first one. It involves the intermediate capping reaction with non-(homo)polymerizable monomers such as i) 1,1-diphenylethylene (DPE) and its derivatives and ii) 2-substitut-ed furans. 

There are other possibilities of suppressing side reaction II. Thus the addition of 1,1-diphenylethylene 18 22) or oxirane 18 23> causes a decrease of the nucleophilicity of the living sites prior to their reaction with VBC. This was especially tested by... 

Differing from the reaction with dinitrogen tetroxide/iodine (see following section), the addition of nitryl iodide to ( )-l,2-diphenylethylene gave a mixture of diastereomers, as determined by H-NMR spectroscopy129. 

Transmetabttwn activator (2, 403). Mctalations of certain secondary benzyl-amines occur more efliciently using TMEDA-activated n-butyllithium than in mctalations with n-hutyllithium alone. Thus N-methylbenzylamine undergoes dimetalation with n-butyllithium-TMEDA predominantly at the nitrogen and o-benzyl positions. Metalation of olefins. Metalation of 1,1-dime hyl-2,2-diphenylethylene (1) with n-BuI.i-TMEDA complex gives the anion (2) in good yield as shown by the reaction... 

Under conditions that are not strictly nonaqueous, the oxidized dimer may be trapped by water, as was observed during the oxidation of 1,1-diphenylethylene catalyzed by the radical cation of dibenzo-1,4-dioxin [91]. The dimer dication upon reaction with water undergoes a 1,2-phenyl shift, resulting finally in 1,2,4,4-tetraphenyl-3-buten-l-one [Eq. (42)], reminiscent of the 1,2-shifts observed during anodic oxidation of 1-phenyl- and 1,4-diphenylnaphthalene in acidic dime thy Iformamide (DMF) [92]. 

Metalation of olefins,3 Metalation of 1,1 -dimethyl-2,2-diphenylethylene (1) with n-BuLi-TMEDA complex gives the anion (2) in good yield as shown by the reaction... 

Chiral bisoxazoline 219 supported on a modified PEG were prepared and employed in combination with CuOTf in the cyclopropanation of styrene and ethyl diazoacetate [140]. As shown in Scheme 3.73, the cyclopropane adduct 221 was obtained in 63% yield and 91% ee trans cis = 77 23). The same reaction with 1,1-diphenylethylene gave the adduct in 45% yield and 93% ee. 

As mentioned earlier, in fluorimetric detection, the amines may be monitored either by natural fluorescence or after derivatization reaction with either 1,2-diphenylethylene-diamine (DPE), trihydroxyindole o-phthalaldehyde (OPA) or fluor-... 

Depending on the nature of the substrate, the polar mechanism may become the only likely possibility. This is the case when non stereospecific functionalisation is observed, as in the reaction of HTIB with stilbenes (142). Another case is the formation of rearranged products, such as in the reaction of 1,1-diphenylethylene (143) with HTIB.240,241 (Scheme 5.19)... 

---