Carbonates diphenylethylene

Norton s group has demonstrated that the insertion of chiral C2-symmetric diphenylethylene carbonate into the Zr-C bond of a zirconaaziridine led to the asymmetric synthesis of an amino acid methyl ester after a subsequent treatment with NaOH in methanol. Since the zirconaaziridine enantiomers interconverted, the reaction was a DKR. It was shown that the efficiency of this process was determined by the balance between the rate of enantiomer interconversion and the rate of insertion. A slow addition of the inserting enan-tiopure carbonate was often required to maximise the stereoselectivity of the reaction, allowing a diastereoselectivity of up to 90% de combined with a quantitative yield to be obtained, as shown in Scheme 1.59. 

These occur readily between electron-rich alkenes and electron-poor carbonyl compounds. The first example, reported in 1959 (64HC(19-2)729), was the formation of 4,4-diaryloxetane-2,2-dicarbonitriles by the room temperature reaction of 1,1-diarylethylenes and carbonyl cyanide. Continued investigation of this reaction shows that a telomerization product is also formed, the tetraphenylpentadienedinitrile (55) from 1,1-diphenylethylene and carbonyl cyanide. This may be interpreted to indicate that carbon-carbon bond formation may commence somewhat ahead of carbon-oxygen bond formation (75MI51302). This... 

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... 

The treatment of alkenes with iodine(III) reagents usually results in functionalization of the carbon-carbon double bond. However, 1,1-diphenylethylene affords a low yield of (l,l-diphenylethenyl)phenyliodonium tosylate with HTIB (equation 181)11,138. The cyclic dithiolylidene derivative of malonic acid, shown in equation 182, undergoes decarboxylation with [bis(trifiuoroacetoxy)iodo]benzene in methanol and gives an unusual vinyliodo-nium trifluoroacetate139. Finally, when the allenylphosphonate shown in equation 183 is added to a mixture of (difluoroiodo)benzene and BF3-etherate in dichloromethane, a... 

The major part of the reactions of a-arylation which have been reported were performed on substrates containing active methylene groups, such as p-diketones, p-ketoesters, P-ketonitriles and malonic acid derivatives. Less activated compounds, such as P-ketosulfides have also been efficiently arylated on the a-carbon. (Table 5.3) The yield of the arylated product can be increased by addition of 1,1-diphenylethylene, acting as a free radical trap. For example, in the reaction of phenylation of ethyl cyclohexanonecarboxylate, addition of 1,1-diphenylethylene reduced the radical chain decomposition in such a way that an 80% yield was obtained instead of 55% in absence of 1,1-diphenylethylene. ... 

These two systems of phenol 0-phenylation [0-phenylation with tetraphenylbismuthonium trifluoroacetate (6) or with triphenylbismuth diacetate (47)] may be ligand coupling reactions involving hexavalent transient intermediates, but no proof of such structures was ever detected. The former reaction does not involve free radicals, as addition of 1,1-diphenylethylene (72) (DPE), did not affect the overall yield. These reactions were explained by a direct aromatic Sn2 displacement, facilitated by the partial charge on the carbon bonded to the bismuth atom.24 (see section 6.6)... 

Noyori was subsequently able to show that triethylamine salts of formic acid (TEAF) could be used to reduce ketones to alcohols and imines to amines with high enantioselectivities [4]. The byproduct of this reaction is carbon dioxide gas and this prevents the possibility of the reverse reaction. Strangely, aminoalcohol ligands are poor in this reaction, whilst unsymmetrical 1,2-diamines have proven very effective. A particularly effective ligand is mono-N-tosyl-l,2-diphenylethylene-diamine. 

Pd-doped organic and carbon aerogels containing between 20 and 40 wt% Pd were demonstrated to be good catalysts in the Mizoroki-Heck reaction of iodobenzene with styrene and 3-butene-2-one in liquid phase to yield franv-l,2-diphenylethylene and frani-4-phenyl-3-butene-2-one, respectively [52], Finally, Eu-doped organic and carbon aerogels were active as catalysts in two Michael addition reactions the reaction of ethyl 2-oxocyclopentanecarboxylate with 2-butenone and with cyclopentenone. Moreover, these catalysts could be recovered and reused [53],... 

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