Bromination of y-butyrolactone

Bicyclo[2.2.1]hepta-2,5-diene, reaction with acetic acid to yield nortii-cyclyl acetate, 46, 74 Bicj clohexyl, 45, 61 2-Biphenylylmagnesium iodide, 46, 94 Bomyl chloride 46, 56 Bromination of y-butyrolactone, 46, 22 Bromine, reaction with i-butyrolactone in presence of red phosphorus, 46, 22... 

Bromine, reaction with y-butyrolactone in presence of red phosphorus, 46, 22... 

The formation of a-bromo-y-butyrolactone has been reported in 70% yield by uncatalyzed reaction of bromine at 160-170°, as well as by the catalyzed procedure used here. ... 

Myadera and Iwai (64CPB1338) have devised a convenient route to the bromide (139 R1 = R2 = R3 = H) starting with commercially available materials (Scheme 84). The anion formed from -y-butyrolactone by the action of sodium hydride was allowed to react with ethyl picolinate to yield the keto lactone (141) which, when heated with hydrobromic acid, undergoes decarboxylation as well as bromination, yielding the bromo ketone (139). Several substituted ethyl picolinates have been used successfully, and it has also been found that the anion of the keto lactone (141) may be alkylated. 

Selective oxidations with bromine. Bromine in combination with this Ni(II) alkanoate promotes the selective oxidation of primary, secondary 1,4-diols to y-butyrolactones (equation I).1... 

Generation of electrophilic halogen. The title reagent has found use in oxidation of KBr to initiate cyclization of homoallylic sulfonamides. The use of the p-anisyl congener to oxidize powdered KBr for benzylic bromination is also realized. 4-Aiylbutanoic acids are converted into y-aryl-y-butyrolactones by this method. ... 

Method Three, Livak et ad. (521). a-Bromo-y-butyrolactone (A) is prepared in 80% yield from y-butyrolactone (commercial avmlable), FBr, and bromine. a-Amino-y-hydroxybutyric acid (B) is prepared in 60% yield by amination of (A). 5-()8-Bromoethyl)-hydantoin (C) is prepared in 51% yield by the reaction of (B) with potassium cyanate to give y-hydroxy-a-ureidobutyric acid (D) and by the HBr hydrolyris of (D). 5-(j0-Methylmercaptoethyl)-hydantoin (E) is prepared in 73% yield from sodium methylmercaptide and (C). DL-Methionine is prepared in 95% yield by the Ba(OH)j hydrolysis of (E). The over-all yield is about 17%. 

Bromoetheriflcation of aikenes can be achieved using NBS in the desired alcohol as the solvent. The reaction of 1,3-dichloropropene with NBS in methanol yields an a-bromo dimethyl acetal in the first step in a convenient synthesis of cyclopropenone. Using propargyl alcohol the reaction depicted in eq 22 has been extended to an annulation method for the synthesis of a-methylene-y-butyrolactones. Intramolecular bromoetheriflcation and bromoamination reactions are generally very facile (eq 23). In natural products synthesis, bromoetheriflcation has been used for the s)mthesis of cyclic ethers (by subsequent de-bromination, see tributylstannane) and for the protection of alkene appendages as cychc bromoethers (regenerated by reaction with zinc). ... 

Regioselective oxidation of primary, secondary 1,4-dioIs with bromine and a nickel(ii) salt provides y-substituted butyrolactones in good yields. The tetrahydrofuran (104, R = Me) is also oxidized regioselectively with chromic anhydride to the lactone (105) in low yield, but the reaction has been used in the synthesis of compounds related to methylenomycin. However, the... 

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