Thiophene analogues

Examples of the remaining potential 3,4-dihydroxy heterocycles are presently restricted to furan and thiophene. Although the parent 3,4-dihydroxyfuran apparently exists as the dioxo tautomer (86), derivatives bearing 2-alkyl or 2,5-dialkyl substituents prefer the keto-enol structure (87) (71T3839, 73HCA1882). The thiophene analogues also prefer the tautomeric structure (87), except in the case of the 2,5-diethoxycarbonyl derivative which has the fully aromatic structure (88) (71T3839). 

A notable utilization of the Hinsberg procedure was executed in the synthesis of a thiophene analogue of porphyrin. A previous synthesis of the tetrathioporphyrin dication of 7 found this material to be unsuitable for chemical exploration as a result of its limited accessibility and solubility. Efforts by Vogel et al. were then directed toward... 

If the displacement reaction is carried out between imidazole derivative and thiophene analogue the antifungal agent tiaconazole (40) results. A rather slight variant of... 

The thiophene analogue (51) of the natural antifeedant product tonghaosu has been prepared <96TL893>. Several acetylenic thiophene derivatives including 52 have been isolated from Blumea obliqua and characterized <96MI733>. 

Thienoimidazothiazole 34 and two isomers were synthesized <1998JHC923> as thiophene analogues of the immune modulator TILOMISOL by cyclizing appropriate 3-oxo thioethers of thienoimidazoles. In contrast to the benzene analogue, no intermediates were observed at this step. 

A similar reaction of thiophene analogues of Troger s base with formaldehyde was carried out by Kobayashi et al. <2002J (P1)1963>. 

If the displacement reaction is carried out between imidazole derivative and thiophene analogue the antifungal agent tiaconazole (40) results. A rather slight variant of this sequence produces antifungal sulconazole (41).Obvious variants of the route explicated above for ketoconazole (34) lead to parconazole (42)and doconazole (43),instead. 

Formylbenzeneboronic acid reacts with hydroxylamine to give a cyclized oxime (200), and the thiophene analogue (201) was prepared in a similar way. These fused 3//-1,2,3-azoxaborines are analogs of the above-mentioned 2,3-dihydro-l,2,3-diazaborines. Compound (200) is resistant to hydrolysis and air, but cannot be converted to its 5-methyl derivative. 

Furan[10] and its 2-formyl derivative (Eq. 5) [11] are arylated at 2- and 5-posi-tions, respectively. Arylation of 3-ethoxycarbonylfuran and its thiophene analogue occurs selectively at the 2-position in toluene, whereas the 5-position is attacked preferentially in NMP (Eq. 6) [12], It has been proposed that paths b and a, respectively, predominantly participate in the former and latter reactions. 

Thienyldihydrothiophene is the thiophene analogue of the phenyl-cyclohexadiene intermediate deduced by Fields and Meyerson (1966c) from scrambling of protium and deuterium in pyrolysis of deuteriated benzene. Both intermediates account for the formation of dimeric species unaccompanied by highly energetic free hydrogen atoms. 

Reaction of the thiophene analogue of the Troger s base 15a with 3 molar equivalents of BuLi, followed by quenching with D20, resulted in the regioselective formation of 2,7-dideuterio derivative 15c in 53% yield. 

The presence of a proton-acceptor site external to the ring such as an aldimine group at the 3-position leads to the possibility of four tautomeric forms, 251-254 (Scheme 21) <1970GHE1232>. A similar behavior is also observed in the corresponding benzo[3]thiophene analogues <1974JPR970>. 

In earlier investigations by the author [1] poly thiophene analogues containing phenylene, (1), were prepared and used as semiconducters in thin film field effect transistors. 

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