Pyrroles alkene coupling

The cycloaddition reactions of isoquinolinium species produce fused isoquinoline products. The Af-ylide of 53, formed with base addition, couples with alkenes <99S51> or imines <99T7279> to afford tricyclic products, such as 54. Pyrrole-fused isoquinolines result from the reaction between mUnchnone imine intermediates and a,yff-ethylenic esters <99EJOC297>. N-Arylimides undergo 1,3-dipolar cycloaddition with strained frani-cyclooctenes, as opposed to common cycloalkenes, to tdford the pyrazolidine-fused ring system <99H(50)353>. 

Ranu, B.C. and Hajra, A., Synthesis of alkyl-substituted pyrroles by three-component coupling of carbonyl compound, amine and nitro-alkane/alkene on a solid surface of silica gel/alumina under microwave irradiation, Tetrahedron, 2001, 57, 4767-4773. 

Pyrrole and iV-methylpyrrole form exciplexes with a variety of arylalkenes and arylalkynes. When pyrrole is irradiated in the presence of styrene the adduct (27) is formed in 67% yield. The reaction is brought about by an electron-transfer process with the amine as the donor and the alkene as the acceptor. Ultimately coupling affords the final product. An analogous addition is seen with 1-methylstyrene when the adduct (28, 52%) is produced. Other examples of such additions were also described. ... 

Topics reviewed during the year include the photochemistry of indoles, sulfoxides, pyrazoles and isothiazoles, (S-hetero)cyclic unsaturated carbonyl compounds, photoinduced single electron transfer (SET) reactions of amines and of azo compounds, SET reactions of organosilanes and organostannanes with Qo and ketones, photochromic polypeptides and di(hetero)arylethenes, processes in chromophore sequences on a-helical polypeptides,aryl-aryl coupling in furans, thiophenes and pyrroles," [3+2]cycloaddition of aromatic nitriles (and esters) with alkenes, and reactions of benzylsilane derivatives. ... 

Regjoselective C—H alkenylation of N-methyl-4-aryl-lH-pyrrole carboxylates (88) with alkenes—primarily acrylamides, acrylates and acrylonitrile—was observed by Lin, Yao, and coworkers to be dependent on the solvent used in the coupling (2014OL4884). As such, C-2 selectivity (89) was achieved when toluene was used as the solvent while inclusion of DMSO favored the C-5 product (87). The authors postulated that the carboxylate-assisted chelation of the palladium catalyst, which occurs readily in toluene, is overridden in the strongly coordinating solvent DMSO and results in an electrophibc C—H activation at the more electron-rich C-5 position. An apphcation of this work to the total synthesis of (it)-rhazinilam was also described in this account. 

The coupling of alkynes and iminocarbene complexes (e.g., 4, Scheme 17.2) affords pyrrole ring systems (e.g., 6) in a formal [3-1-2]-cycloaddition process [2,3]. The pyrroles obtained are analogous to those obtained from nitrile ylide cycloadditions. A mechanism was proposed involving a net metalla-[4- -2] cycloaddition to afford azametallacycle 7 followed by reductive elimination and alkene isomerization. The regiochemistry arises through a nonconcerted addition to the triple bond via... 

Similarly, Huestis and Fagnou reported a cationic Rh-catalyzed preparation of unsymmetrically substituted pyrroles from the coupling of enamides with enynes in good yield (Eq. (5.24)) [5c]. In this reaction, alkenes were selectively introduced at the C2 position of the corresponding pyrroles by using a Rh-catalyzed vinylic... 

The CDC reaction of arenes and alkenes can be applied to heteroaromatic compounds. Coupling with furan, thiophene, pyrrole, benzofuran. 

Heteroaromatic compounds show similar behavior to benzene derivatives. Furan, pyrrole, thiophene, benzofuran, indole, benzothiophene, and their related compounds undergo CDC reactions with alkenes. In the case of furan, the coupling reactions with acrylates, acrylonitrile, styrenes, and... 

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