Geranyl bromide

The reaction mixture is poured into 1 1. of cold water, and the precipitated product is collected by filtration and washed with cold water until the wash water is colorless. The solid is then washed with cold methanol (500 ml.) and recrystallized from methanol using 25 g. of activated carbon. There is obtained 35.9, g. (63%) of a-furil as yellow needles melting at 165-166°. 

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The preparation of coenzyme Q usually iavolves either 2,3-dimethoxy-5-methylbenzoquinone or hydroquiaone as the starting material. Treatment of the hydroquiaone with geranyl bromide followed by oxidation affords (61, n = 2) (214). A facile and efficient preparation of ubiquiaone-10 (61, n = 10) has been developed (215). 

C2]-Squalene, 80, has been produced71 in the reaction sequence shown in equation 31 which involves alkylation of 3-13C-ethyl acetoacetate with geranyl bromide, followed by hydrolysis, decarboxylation and treatment with triethyl phosphonoacetate and then reduction of the ester 82 with LiAlHr, bromination with CBr4/PPh3 and coupling the farnesyl bromide with Cul/Li-pyrrolidine. Epoxidation of 80 has been effected by... 

Methyllithium (prepared from methyl chloride), available from Foote Mineral Company, can be used without further purification. Attention should be drawn to the following methyllithium purchased from Alfa Inorganics is prepared from methyl bromide and thus produces a mixture of geranyl bromide and chloride. 

A new synthesis of nerolidol (10) from geranyl bromide has been achieved by the use of the hydroxy-sulphoxide (9)/ a new prenylating agent (Scheme 3)7 ... 

Reagents i, PhSH-02 ii, BuLi iii, geranyl bromide iv, Li-EtNH2... 

Condensation of 2 fluoroacetoacetate with geranyl bromide leads, after basic hydrolysis, to 3-fluorogerany lacetone The latter is an intermediate for the synthesis of 4-fluorofarnesol [775] (equation 100)... 

Various approaches to the synthesis of menaquinones have been made, in which the aromatic component is activated to encourage nucleophilic attack upon a receptive prenyl fragment. Thus alkylation of the potassium salt of 2-methyl-1,4-naphthoquinol (236) or 4-methoxy-3-methyl-l-naphthol (237) with geranyl bromide (244) gave menaqui none-2 (246) in 20 and 45% yield, respectively, after oxidation. Hydrogenolysis of the dimethyl ether (238) of 1 -oxymenaquinol-2 [from... 

First, treat geraniol with PBr3 to form (CH3)2C=CHCH2CH2C(CH3)=CHCH2Br (geranyl bromide). 

A related selectivity question is answered with the reactions of (ii)-geranyl bromide (eqnation 135). Complexation gives a noncrystalline residne that conples with cyclohexyl iodide on heating in DMF, bnt the coupled product shows... 

Use of the 1 1 complex of N-bromosuccinimidc and dimethyl sulfide in place of (1) similarly converts allylic and benzylic alcohols into the corresponding bromides in 80-90% yield. For example, geraniol was converted into geranyl bromide in 82% yield. 

For example, the reagent reacts with frans-geranyl bromide (1) to give /i-ans-homo-geranyl cyanide (2) in 92% yield. The reaction is carried out in the following way. A cooled solution of n-butyllithium (2.0 ml., 1.3 Af) pentane is added to a solution of... 

Y,7-Dimethylallyl bromide and geranyl bromide are converted into the corresponding aldehydes in 75 and 82% yields, respectively, by heating at 100 °C with sodium dichromate in hexamethylphosphoramide in the presence of dicyclohexyl-18-crown-6 ether [614]. Similar results are achieved with polymer-supported chromic acid [540] (equation 192). 

Other applications of carbanions a to a sulfone in total syntheses have recently been reported. Most of them used allylic sulfones or allylic halides. Two examples are reported here. In the synthesis of a precursor of cembranolides, a sulfone derived from geranyl bromide was coupled with an allylic alcohol epoxide (Scheme 65). An interesting point was that the coupling reaction gave high yields only when the lithiated sulfone was allowed to react with the epoxymagnesio alkoxide (the lithium salt of the epoxy alcohol did not react at all with the lithiated sulfone). 

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