Bromocrotonates, Reformatsky reactions

The 3,4-dihydrodiol of BcP was synthesized from 4-oxo-l,2,3,4-tetrahydro-BcP (15) by Method I (66). The ketone L was itself prepared from 4-oxo-l,2,3,4-tetrahydrophenanthrene via a multistep sequence entailing Reformatsky reaction with methyl bromocrotonate, dehydration of the resulting alcohol, isomerization to the aryl-butyric acid, and cyclization of its acid chloride with SnCl - Full... 

Methyl crotonate reacts with NBS and brominates is allylic position giving methyl 3-bromocrotonate, a valuable synthetic reagent used in Reformatsky reaction. 

The influence of a Lewis acid in favouring the ring closure was confirmed by the use of a catalytic amount of CpiTiCL in imino-Reformatsky reactions with a-bromoesters, -bromocrotonates and a-bromomethylacrylates the corresponding cis /9-lactams were obtained in excellent yields in THF at rt129. 

TABLE 5. Reformatsky reaction of 4-bromocrotonate 191b with benzalacetone... 

Reformatsky reaction.5 The Reformatsky reaction of y-bromocrotonic acid with aldehydes or ketones in THF gives rise to a mixture of branched and linear unsaturated hydroxy acids. The former are the kinetic products and, on equilibration, rearrange to the latter products. 

Two simple applications may be mentioned. With cyclohexene, 3-bromo-cyclohexene is obtained in a satisfactory yield (Expt 5.68), the latter upon dehydrobromination with quinoline affords an 80-90 per cent yield of cyclo-hexa-1,3-diene (Expt 5.13). Methyl crotonate yields the valuable synthetic reagent methyl y-bromocrotonate (Expt 5.69) this latter compound permits the introduction (in moderate yield) of a four-carbon atom chain at the site of the carbonyl group by the use of the Reformatsky reaction (compare Expt 5.170) ... 

Fig (23) Acid (193) prepared from bromoanisole (190) by standard organic reactions, undergoes cyclization with polyphosphoric acid leading the formation of tetralone (194). A Reformatsky reaction on compound (194) with methyl g-bromocrotonate followed by aromatization produces compound (195). It is converted to compound (196) by treatment with methylmagnesium and cyclization. The corresponding phenol was oxidized to miltirone (197). 

Reformatsky reaction of A-bromocrotonate. The regioselectivity of the Refor-matsky reaction of ethyl 4-bromocrotonate with cyclopentanone (equation I) is markedly dependent on the solvent and catalyst, a-Addition is favored in ether, whereas y-addition... 

The Reformatsky reaction of 4-bromocrotonate esters with conjugated enones can conceivably give four regioisomers, as shown in equation (27). Several workers have applied such reactions to the synthesis of vitamin A and related compounds. In most cases, 8-lactones derived from 1,2-7-adducts were obtained, as exemplified by results with -cyclocitral (equation 28). ... 

Uses Solvent for paints, electrochemistry, polymer and boron chemistry, physical processes such as gas absorp., extraction, stabilization, industrial prods, such as fuels, lubricants, textiles, pesticides process solvent/solubilizer pharmaceutical solvent, vehicle in the Reformatsky reaction with methyl bromocrotonate Manuf./Distrib. Aldrich Brand-Nu Eabs Ferro/Grant Fluka Sigma Spectrum Quality Prods. 

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