1.2-Phenyl shifts

Presumably, 9 is actually formed from carbene 8 in the pyrolysis zone by a P/C phenyl shift, but then apparently succumbs to fast transformation into the thermodynamically stable final products. Formation of the methane derivative 13 should be preceded by a 1,2-phenyl shift to give the shortlived 10, the production of fluorene (14) by the occurrence of diphenylcarbene (II), and the formation of benzophenone (15) by isomerization to the angle-strained three-membered heterocycle 12, which is followed by elimination of phenylphospbinidene. No direct evidence is available for the intermediacy of 10-12. 

In the presence of AgOTf, the reaction of 1,3,3-triphenylpropadienyl chloride with an amine in CH3CN resulted in the formation of iminium triflate 136 via a 1,2-phenyl shift process [67]. 

The oxazole-fused pyrimidinethione 149 has been used as a source for generation of heterocumulene 151, an imine of carbon suboxide82. Under FVP conditions at 900°C, ring opening accompanied by a 1,2-phenyl shift first gives 150, which then loses HNCS and HCN to give the product that was characterized by IR in a matrix at 18 K. 

Farnia and coworkers have described a novel 1,2-phenyl shift which takes place during the electrochemical reduction of the indenes 2 (equation 4)11. Mechanistic experiments demonstrated that rearrangement takes place at the dianion stage. 

Therefore, from epoxide 83 (Scheme 5.38), a 1,2-phenyl shift in intermediate MM would provide oxonium derivative NN, which would furnish, after rearrangement of the oxetane intermediate OO, the desired ketone 84. It is interesting to note that on the same substrates cationic gold derivatives (activated with silver salts) did not lead to the same final compounds, showing the unique reactivity of silver salts. 

TABLE 12.6. Conditions and Yields for the 1,2-Phenyl Shift in Diphenylallenyl Ketones... 

A reaction of acetyldimethylphenylsilane 166 with TBAF 3II20 in THF or with KF in DMS0/H20 gave [Me2SiO]v (167) and 1-phenylethanol 168 quantitatively (equation 100). The reaction was considered to involve a 1,2-phenyl shift followed by a Brook rearrangement (equation 101 )229. 

Zimmerman 103) applied the well known rearrangement of 4,4-disubstituted cyclohexa-2,5-dienones (e.g. the 4,4-diphenyl derivative tives the 3,4-disubstituted phenols l)). Using acetic anhydride and a small amount of concentrated sulfuric acid, 97.5 % of 3,4-diphenylphenolacetate is formed, which in turn is hydrolyzed to give 3,4-diphenylphenol. This is one of the easiest synthesis of this phenol. 2-Bromo-4,4-diphenylcyclohexa-2,5-dienone rearranges by a similar route to give a 49 % yield of 2-bromo-3,4-diphenylphenolacetate and 47 %2-bromo-4,5-diphenylphenolacetate U4). A [1.2]-phenyl shift of 4-methoxy-2,3,4,6-tetraphenyl-2,5-dienone in acetic anhydride and zinc chloride gives rise to 4-methoxy-2,3,5,6-tetraphenylacetate (m.p. 284 °C, 85% yield)115 . 

The results also gave a further support to the 1,2-phenyl shift mechanism since a random migration of the phenyl group via a symmetrical rt-complex (cf. [281] and [282]) contradicts the observed behaviour. The rate of the... 

The mechanism of this reaction involves formation of an intermediate carbo-cation, a 1,2-phenyl shift, and loss of a proton to form the product ... 

The 7-sultam derived from the four-membered ring having two /ra j-oriented phenyl groups is obtained in better yield because the /ra /-orientation favors the 1,2-phenyl shift (see Section 4.05.3.2.1) <1998T8941>. 

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]. 

A 1-2-phenyl shift occurs especially easily. In the acid fission of 2-(a-phenylethyl)-3-isopropyloxazirane (20) aniline was isolated as the sole basic fission component. Of the two available groups,... 

Five enol ethers are produced, two unrearranged (41), one 1,2-phenyl-shifted (42) and two 1,2-methyl-shifted (43). Unlike the corresponding thermal reaction (see Scheme 31 and Table 11), the product patterns are barely affected by the geometrical structure of 40 the ratio 41/42 -h 43 = 2.0 for -40 and 1.8 for Z-40. This indicates formation of a common intermediate, the primary vinyl cation 49, from both stereoisomers (Scheme 55). This cation gives 41 and rearranges to the more stable vinylic cations 46-48, which in turn give 42 and 43. 

We propose that the reaction of acetals of 2-bromopropiophenone constitutes a test to distinguish between the different types of acid sites in a metal ion exchanged large pore zeolite. Thus, while Bronsted or hard Lewis sites produce hydrolysis of the acetal moiety, 1,2-phenyl shift leading to 2-phenylpropanoate is catalyzed by soft and borderline Lewis sites. Moreover, the ratio between phenyl or alkoxy migration products appears to be controlled by the softness-hardness of the centers. A new large pore zeolite with two framework compositions (ETAS and ETS) have also been studied and it has been found that their chemical behavior is Intermediate between Y and X faujasite. 

The data on the 1,2-phenyl shift have been taken from M. I. Rudnev s diploma thesis (Novosibirsk, 1980) and specified by V. A. Bushmelev... 

It is interesting to note that the nine-membered macrocycle must be the result of homocouphng of the corresponding nine-membered bisboronate. With these macrocycles in hand, Jasti developed a reductive aromatization technique that circumvented the 1,2-phenyl shift observed under acidic or Lewis acidic conditions for similar systems (Fig. 22) [61]. 

Photolysis of arylalkyldiazo compounds by steady-state, triplet-sensitized, and LFP showed that 1,2-hydrogen and 1,2-phenyl shifts can be significantly accelerated by increasing solvent polarity and by a phenyl substituent at the carbon bearing the migrating group. ... 

III. Attack of the ruthenium center of species III at the remote benzyl carbon with a concomitant 1,2-phenyl shift would give rise to the cyclobutylmthenium species... 

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