2-Iodo 5 nitrothiophene

Toward the end of the distillation a small amount (0.5-2.0 g.) of 2-iodo-5-nitrothiophene is collected in the condenser and the receiver. The amount formed increases with increase in the temperature of the reaction mixture. 

Nitro-[2,2 5, 2"]terthiophene has been prepared by palladium-catalyzed Negishi cross-coupling between 2-iodo-5-nitrothiophene and the organozinc derivative of bithiophene. The latter was obtained from the corresponding lithio derivative (Scheme 66). 

P-Methylstyrene has been photooxidised to cinnamaldehyde by irradiating in the presence of 2-iodo-5-nitrothiophene, and a time-resolved study of the irradiation of a series of substituted styrenes embedded in acidic and non-acidic zeolites has appeared. ° In this latter case, the corresponding radical cation is produced for which the zeolite framework provides a stabilising effect whose strength is dependent upon the nature of the substituents. 

Photosubstitution of the nitro group in 2-nitrothiophene has been reported <94TL633>. Thus, photolysis of 2-nitrothiophene in the presence of indene in acetonitrile gave (495) in excellent yield. Similarly, photolysis of 2-iodo-5-nitrothiophene in the presence of indene gave a 3 1 mixture (total yield quantitative) of (496) and (495). 

Additionally, several donor/acceptor-substituted ter- and quaterthiophenes were synthesized in order to gain series with varying chain lengths. Thus, MeO-Tj-ZnCl 427 was cross-coupled with Br—Tj—H 50 and resulted in 5-methoxy terthiophene MeO-Ts-H 428 in 53% yield, the homo-coupling products MeO-T2-OMe 429, and H-T4—H 4 [Eq. (106)]. Subsequent coupling of MeO-T2-ZnCl 430 and MeO—T3-ZnCl 431 with 2-iodo-5-nitrothiophene... 

Addition-elimination (for the chloro compound) and elimination-addition (via an intermediate haloalkyne, for the bromo and iodo compounds) mechanisms account for the activation parameters determined for reaction of 2-(/3,/3-dihalovinyl)-5-nitrothiophenes with MeONa-MeOH. °°... 

A completely different behavior was reported for the photochemical interaction between halogenonitrothiophenes and arylalkenes. When 5-iodo-2-nitrothiophene (121) was irradiated in the presence of styrene, the formation of a mixture of nitrones 149 and 150 was observed. The same behavior was observed by using nitroarenes, such as nitrothiophene or nitrobenzene (94JPP(A)(79)67). The reaction can be explained on the basis of a work published in 1955 where an electron transfer mechanism was proposed. The radical thus formed can give the product of addition of the nitro group to the double bond that, then, can be converted into the product (55JOC1086). 

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