3-bromo-3-phenylpropionic acid

Even more striking is the spectrum of 3-bromo-3-phenylpropionic acid, which first loses a bromine radical, then ketene. The rearrangement fragmentation is supported by a metastable peak at m/z 76.8 (107 /149 = 76.84). The stability of the benzylic product ion and the stability of the neutral ketene molecule provide the impetus for this rare rearrangement of a hydroxy group (Equation 2.87). 

Bnnton, C.A., Kamego, A.A., Ng, P. Micellar effects npon the decomposition of 3-bromo-3-phenylpropionic acid effect of changes in snrfactant structure. J. Org. Chem. 1974, 59(24), 3469-3471. 

Not unexpectedly, alkylation of the double carbonylated complex proceeds via a base-catalysed interfacial enolization step, but it is significant that the initial double carbonylation step also involves an interfacial reaction, as it has been shown that no pyruvic acid derivatives are obtained at low stirring rates. Further evidence comes from observations of the cobalt-catalysed carbonylation of secondary benzyl halides [8], where the overall reaction is more complex than that indicated by Scheme 8.3. In addition to the expected formation of the phenylacetic and phenylpyruvic acids, the reaction with 1-bromo-l-phenylethane also produces 3-phenylpropionic acid, 2,3-diphenylbutane, ethylbenzene and styrene (Scheme 8.4). The absence of secondary carbonylation of the phenylpropionylcobalt tetracarbonyl complex is consistent with the less favourable enolization of the phenylpropionyl group, compared with the phenylacetyl group. 

A similar sequence probably accounts for the formation of 50% (40%) 1-clilo-ro- (1-bromo-) -2-methoxy-2-phenylpropionic acid by electrolysis of cinnamic acid in CH30H/NH4C1 (NH4Br)as SSE 271 Electrolysis of irans-stilbene in me-thanol/NH4Br produces eryr ro-stilbene dibromide and l-methoxy-2-bromo-1,2-diphenylethane 1 °4-1 in fair yields. 

Bromo-4-methoxytoluene, 26, 51 o-Bromo- -methylanisole, 23, 12 -Bromo-/3-m ethylvaleric acid, 21, 61 a-Bromonaphthalene, 21, 89 6-BROMO-2-NAPHTHOL, 20, 18 wt-Bromophenol, 23, 12 a-BROMO-/3-PHENYLPROPIONIC ACID, 21, 100... 

This method is exemplified in Organic Syntheses519 by the synthesis of 2-bromo-3-phenylpropionic acid which is important for preparation of DL-phenylalanine.5 80... 

Phenylalanine has been prepared by the action of ammonia and hydrogen cyanide upon phenylacetaldehyde,1 by the reduction of the oxime of phenylpyruvic acid,2,3 by the action of ammonia on a-bromo-j3-phenylpropionic acid,4 and by the reduction of a-aminocinnamic add or its derivatives by means of sodium amalgam with water,5,6 or red phosphorus with hydriodic acid.7,8... 

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