Grignard compounds furan

The chemistry of benzo[Z>]furan-2(3//)-one (395) which exists in the keto form, is that expected of the lactone of 2-hydroxyphenylacetic acid. Grignard reagents bring about the expected ring opening. Condensations may be effected at the 3-position, especially with aromatic aldehydes. Methylation with iodomethane and potassium carbonate in DMF furnishes the 3-methyl and the 3,3-dimethyl compound. Methylation, with diazomethane,... 

Grignard reagents are difficult to prepare in both the furan and benzo[f ]furan series and their use has been superseded by the more tractable lithio compounds. Bromofurans are best converted into the Grignard reagents by treatment with a copper-magnesium alloy in THF (80JOC3125). 

Without the disadvantage of using diazo compounds in the first step, Wenkert s latest monoterpenoid syntheses would be most efficient approaches, and in any case represent novel routes to well-known materials. Nezukone (754) was the result of examining the reaction between butadiene and diazopyruvic ester catalyzed by rhodium tetraacetate. The major product of the addition was the cyclopropane 758 (Scheme 62). It was known that divinylcyclopropanes could be thermolyzed to cycloheptadienes (Vol.4, p.537, Ref.600). The Wittig product from 758 thus gives a cycloheptadiene, and subsequent steps are shown in the scheme. The last step involves Grignard addition to the ester function of the enolate, then loss of water and redistribution of the double bonds.(Further examples of the use of diazo compounds will be found under perillene in the section on furans.)... 

A mixture of 2-t-butylfuran and 2,5-di-t-butylfuran is obtained by the action of t-butyl chloride on furan in the presence of mesitylene nolybdenum tricarbonyl." The intermediate in the nitration of furan-2-aldehyde in acetic anhydride has been identified as compound (26). Treatment of 5-bromo-2-furoic acid with sulphur tetrafluoride in hydrogen fluoride yields the dihydrofuran (27). Bromo-furans are converted into aryl-furans by crosscoupling with aryl Grignard reagents in the presence of nickel(II)-phosphine complexes. 2-Furoic acid is lithiated at position 5, 3-furoic acid at C-2. 2-Methylfuran yields the 5-methylthio-derivative by lithiation and subsequent treatment with dimethyl disulphide. The corresponding phenylthio-compound (28) has been converted into a series of 4-substituted 2-methyl-furans (29 R = alkyl, MeaSi, CO2H, or RCHOH) by the sequence bromi-nation, lithiation, treatment with the appropriate electrophile, and, finally, desulphurization with Raney nickel. 2-Lithiofuran reacts with copper(II)... 

A great deal of carbanirms, generated from C-H-active compounds, the Grignard reagents, the cyanide ion, all kinds of organometallic carbon-lithium derivatives, aromatic amines, phenols, pyrroles, indoles, thiophenes, furans, and other organic compounds with electron-rich carbon atoms have been involved in the Sn reactions as C-nucleoplules [1, 2, 10, 11, 114—117]. 

The furan reaction was shown to be an equilibrium, and to be catalyzed by mercuric chloride 116). Tris(2-furyl)arsine has also been prepared by Wurtz-Fittig and Grignard procedures 119). The most recent use of mercury compounds has been in the preparation of dichloroperfluorovinyl-arsine 120,121). 

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