2- Thienylmagnesium bromide, reaction with

In a similar sequence, reaction of ketoester 52 with 2-thienylmagnesium bromide gives a modest yield of the benzilic ester 53. Transesterification of this with aminoalcohol 51, prepared analogously to 45 by starting with methylamine, gives, after quaternization with methyl bromide, heteronium bromide... 

Advantage has been taken of the aforementioned observations in the synthesis of a terthiophene natural product, arctic acid (147) [123]. Pd-catalyzed carbonylation of bromobisthiophene 25, obtained from the Kumada coupling of 2-thienylmagnesium bromide and 2,5-dibromothiophene, gave bithiophene ester 144, which was converted to iodide 145 by reaction with iodine and yellow mercuric oxide. Subsequent propynylation of 145 was then realized using the Sonogashira reaction with prop-l-yne to give bisthienyl alkyne 146, which was subsequently hydrolyzed to 5 -(l-propynyl)-2,2 -bithienyl-5-carboxylic acid (147), a natural product isolated from the root of Arctium lappa. 

Rossi and associates described a Kumada coupling of 2-bromofuran with 2-thienylmagnesium bromide to assemble thienylfuran 11 [19], The reaction proceeded readily at room temperature. 

Grignard compounds in the thiophene series were studied (20) and used for the synthesis of some thienylbutenols. The product obtained by the reaction of alpha-thienylmagnesium bromide with butadiene monoxide has been identified as 4-(2-thienyl)-buten-2-ol-l formed by 1-4 addition. Furthermore, the Grignard compounds were utilized for... 

Di(3-benzo[6]thienyl)methane is obtained by treatment of 3-benzo-[6]thienylmagnesium bromide with 3-chloromethylbenzo [ thiophene.486 Two molecules of 3-benzo[6]thienylmagnesium iodide may be coupled by treatment with cupric chloride,305 but not with cupric bromide or nickel bromide,349 to yield 3,3 -di(benzo[6]thienyl). A claim349 to have prepared the same compound by the Ullmann reaction is probably not justified.305 The Ullmann reaction otherwise seems to be of general application in the benzo [6]thiophene series.87-483 Halobenzo[6]thiophenes76 105 511 can be selectively metallated in the 2-position by the use of w-butyllithium (Section VII). 

The relatively inactive vinyl halides have been employed with some success in this reaction. a>Thienylmagnesium bromide is coupled with vinyl chloride in the presence of cobaltous chloride to give a-vinylthio phene (29%). Also, the coupling of vinyl and allyl bromides by mag nesium-coppet alloy produces the diolefin, 1,4-pentadiene, in 15% yield. Other diolefins have been prepared by this method. Biallyl is... 

Thienylmagnesium bromide is reported to undergo an exothermic coupling reaction with 3,6-dichloropyridazine in the presence of catalytic bis(l,3-diphenylphosphino)propane nickel(II) to give... 

The preparation of 2-thienylcerium reagent has been referred to in Section 2.10.4.7.1. This reagent reacts with spirodiketones to form the corresponding alcohols <91CC1614>. Apparently 2-thienyllithium fails in this reaction, but excess 2-thienylmagnesium bromide can be used instead of the cerium reagent. 

Several tricyclic monomers required for oxidative (electrochemical or chemical) polymerization have been prepared by coupling reactions. Thus, l,4-diiodo-2,5-dimethylbenzene was coupled with 2-thienylmagnesium bromide in the presence of nickel(II) bis(diphenylphosphino)propane dibromide (NidpppBr2). However when methoxy groups were present in the benzene ring ortho to the site of coupling, the decreased electrophilicity necessitated the use of a more nucleophilic thiophene derivative, 2-thienylcopper (Equation (60)). 

Thienylmagnesium or zinc derivatives can be coupled with vinyl halides, bromo- or iodo-benzene, or ethynyl bromide under Ni or Pd catalysis (Equation 8). The reaction can be extended to the synthesis of (3-styrylthiophene in this case the double-bond configuration is retained in the product. 

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