Nitrothiophenes structure

The nitration of 2-phenylthiophene gives two isomeric 2-phenyl-nitrothiophenes the structures of which have not been proved. ... 

Recently, nitration of organolithiums and Grignards with N204 has been developed for the preparation of certain kinds of nitro compounds (Eqs. 2.14 and 2.15).31 The success of this process depends on the reaction conditions (low temperature) and the structure of substrates. For example, 3-nitrothiophene can be obtained in 70% overall yield from 3-bromothiophene this is far superior to the older method. 3-Nitroveratrole cannot be prepared usefully by classical electrophilic nitration of veratrole, but it can now be prepared by direct o>7/ o-lithiation followed by low-temperature N204 nitration. The mechanism is believed to proceed by dinitrogen tetroxide oxidation of the anion to a radical, followed by the radical s combination. 

Some theoretical aspects of thiophene reactivity and structure have also been discussed, for example the kinetics of proton transfer from 2,3-dihydrobenzo[6]thiophenc-2-onc <06JOC8203>, the configuration of imines derived from thiophenecarbaldehydes <06JOC7165>, and the relative stability of benzo[c]thiophene <06T12204>. The kinetics of nucleophilic aromatic substitution of some 2-substituted-5-nitrothiophenes in room temperature ionic liquids have also been investigated <06JOC5144>. 

The regioselectivity of the VNS process is dependent mi substituents oti the thiophene ring, the structure of the carbanion and the reaction conditions. Nucleophilic addition to 2-nitrothiophene can occur at two positions C-3 and C-5, but the strong preference is for attack at C-3 [168]. 

Red crystals formed from the reaction of 2-nitrothiophen with aliphatic secondary amines in the cold are tentatively assigned the structure R2NCH=CHCH=C(N02) 2Sj a very similar cleavage reaction with amines involving a stable five-membered heteroaromatic system, 2-bromo-5-nitrothiazole, was reported some time ago. "... 

The reaction between 2-nitrothiophen and secondary aliphatic amines leads most probably to the ring-opened product (213). Raney-Nickel desulphurization continues to play an important role in the structure determination of thiophen derivatives, and for the synthesis of macrocyc-lic compounds, such as a-alkylcycloalkanones, amino-lactams of aliphatic diaminocarboxylic acids, and of dethiobiotin. The nickel boride catalyst (NiBo), prepared from nickel(ii) chloride and sodium borohydride in methanol, gives olefins in 50—55% yield. From (214) a mixture of methyl... 

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