2-Thienylmagnesium iodide

Alternative methods of preparing the starting acids can be used, but are generally less convenient. Benzo[6 ]thiophene derivatives were prepared from 2-methyl-3-(2 -thenoyl)propionic acid, which was obtained either by reacting 2-thienylmagnesium iodide with methylsuccinic anhydride, or by coupling 2-bromoacetylthiophene with the sodium salt of diethyl methylmalonate (45JA1645). 

Derivation A heterocyclic alcohol made by reaction of 2-thienylmagnesium iodide and formaldehyde. 

Thenaldehyde has previously been prepared by Steinkopf and Schmitt3 from 3-thienylmagnesium iodide and ethyl orthoformate in low yield. The first application of the method here described was reported by Campaigne and LeSuer.4... 

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). 

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. 

---