Ring closing metathesis reaction (RCM) is an elegant strategy for synthesis of cyclic compounds. In contrast to most other cyclization reactions, RCM succeeds even under conditions of unfavourable ring sizes (>7, 8). Concerning this fact it is no surprise, that a lot of recent total syntheses use RCM as a key step, since macrocycles of the above mentioned size are often part of natural substances. Aim of this work was to investigate, if RCM is capable to transform N,N'-dialkenyl thiophenedi-carboxamides 1 into the corresponding nitrogen heterocycles 2. All combinations of alkenyl chains n,m=1...3 were synthesized. Using ruthenium based catalysts, the influence of substitution pattern and chain length on yield and configuration of the newly formed C-C double bond was investigated. Structures of RCM products 2 were unambiguously resolved by means of 1H and 13C nmr spectroscopy. In some cases, single crystal X-ray measurements were performed additionally. During the studies it turned out, that no reliable synthetic protocol has been published for thiophene-3,4-dicarb-oxylic acid 3, which was required as a key intermediate. So a robust protocol was developed, which does not use laborious separation techniques and therefore is very suitable for multigram syntheses of dicarboxylic acid 3. As alternatively 3 can also be synthesized via the corresponding dicarbonitrile, a practicable synthesis for this intermediate was looked for, too. Nickel catalysed cyanation of 3,4-dibromothiophene turned out to be the method of choice.
Bearing in mind, that heteroaryl carbonitriles are important synthetic intermediates, scope and limitations of the used protocol were investigated. Issues of interest were the influence of the type of the halogen, electronic and steric properties of R, type of cyanide source and the use of ultrasonic irradiation.