3- thienylmanganese bromide

We reported a facile synthesis of 3-bromo-4-thienylmanganese bromide and 4-substituted 3-thienylmanganese bromides via the direct oxidative addition... 

The preparation of 3-thienylmanganese bromide 123 is possible via the direct oxidative addition of Rieke manganese to 3,4-dibromothiophene 116 (Scheme 50)... 

Notably, Rieke manganese is able to take part in oxidative addition even where Rieke zinc or Rieke magnesium is insufficiently reactive [258]. The 3-thienylmanganese bromide intermediate 123 can be coupled effectively with both aryl iodides and aroyl chlorides via palladium catalysis to give the products 124 and 125 in moderate to high yields (Scheme 50, Table 28) [343, 344],... 

As shown in Table 8.18, 3-bromo-4-thienylmanganese bromide was formed as a major product from the reaction of 1 equiv of 3,4-dibromothiophene and 2equiv of Mn [47]. This reagent easily underwent a cross-coupling reaction with acid chlorides and aryl iodides. According to the high-resolution mass spectra of the products of entries 1,4,5, and 6 in Table 8.18, the second bromine atom of the thiophene ring is still retained. 

Table 8.18 Coupling reaction of 3-bromo-4-thienylmanganese bromide.

The same strategy was applied to 4-substituted 3-bromothiophenes to make unsymmetrical 3,4-disubstituted thiophenes. As shown in Table 8.19, crosscoupling products were obtained in moderate yields (36-66%) under mild conditions. Oxidative additions of Mn to the 4-substituted bromothiophenes were performed at rt in 5 h, and the successive coupling reactions of thienylmanganese bromides with benzoyl chlorides afforded unsymmetrical 3,4-disubstituted thiophenes at rt in 30 min without a catalyst (Table 8.19, entries 1 and 2). 

With a Pd(0) catalyst, the C—C bond formation was completed from the reaction of the thienylmanganese bromide with 4-iodobenzene (Table 8.19, entry 3). 

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