Synthesis of Heteroaromatics

Peter Wipf at the University of Pittsburgh utilized (J. Org. Chem. 2013, 78, 167. DOI: 10.1021/jo3022605) an alkynol-furan Diels-Alder reaction to convert 1 into the hydroxyindole 2. An intramolecular Larock indole synthesis was employed (Angew. Chem. Int. Ed. 2013, 52, 4902. DOI: 10.1002/anie.201300571) by Yanxing Jia at Peking University for the conversion of aniline 3 to tricyclic indole 4.

The reaction of boronodiene 5 with nitrosobenzene to produce pyrrole 6 was reported (Chem. Commun. 2013, 49, 5414. DOI: 10.1039/C3CC42227E) by Bertrand Carboni at CNRS-University of Rennes and Andrew Whiting at Durham University. The merger of imine 7 with propargyl amine 8 in the presence of strong base, leading to pyrrole 9, was disclosed (Org. Lett. 2013, 15, 3146. DOI: 10.1021/ol401369d) by Boshun Wan at the Chinese Academy of Sciences. Bin Li and Baiquan Wang at Nankai University found (Org. Lett. 2013, 15, 136. DOI: 10.1021/ol303159h) that pyrrole 12 could be prepared by the oxidative annulation of enamide 10 with alkyne 11 via ruthenium catalysis in the presence of copper(II). Naohiko Yoshikai at Nanyang Technological University demonstrated (Org. Lett. 2013, 15, 1966. DOI: 10.1021/ol400638q) that N-allyl imine 13 could be cyclized to pyrrole 14 via dehydrogenative intramolecular Heck cyclization.

Rhett Kempe at the University of Bayreuth developed (Nature Chem. 2013, 5, 140. DOI: 10.1038/nchem.1547) a "sustainable" pyrrole synthesis in which iridium complex 17 catalyzed the dehydrogenative coupling of alcohol 15 and phenylalaninol (16) to produce pyrrole 18. In a related process, David Milstein at the Weizmann Institute of Science found (Angew. Chem. Int. Ed. 2013, 52, 4012. DOI: 10.1002/anie.201300574) that the ruthenium complex 20 effected the transformation of 2-octanol (19) and 16 to furnish pyrrole 21.

An alternative ruthenium-catalyzed pyrrole synthesis from readily available components was developed (Angew. Chem. Int. Ed. 2013, 52, 597. DOI: 10.1002/anie.201206082) by Matthias Beller, allowing for the preparation of 25 from ketone 22, diol 23, and amine 24. Meanwhile, with a bit of heteroaromatic alchemy, Huw M. L. Davies at Emory University converted (J. Am. Chem. Soc. 2013, 135, 4716. DOI: 10.1021/ja401386z) the furan 26 to pyrrole 28 by reaction with triazole 27 under rhodium catalysis.

Prof. Kempe also developed (Angew. Chem. Int. Ed. 2013, 52, 6326. DOI: 10.1002/anie.201301919) a method for the synthesis of pyridine 30 from amino alcohol 29 and propanol using an iridium catalyst closely related to 17. Copper and secondary amine "synergistic" catalysis was used (J. Am. Chem. Soc. 2013, 135, 3756. DOI: 10.1021/ja312346s) by Prof. Yoshikai for the construction of pyridine 33 from oxime 31 and cinnamaldehyde (32). Tomislav Rovis at Colorado State University developed (J. Am. Chem. Soc. 2013, 135, 66. DOI: 10.1021/ja3104389) a rhodium-catalyzed procedure to generate pyridine 35 from unsaturated oxime 34 and ethyl acrylate, which proceeded with very high regioselectivity. Finally, the copper-mediated preparation of furan 38 from propiophenone (36) and cinnamic acid (37) was reported (Org. Lett. 2013, 15, 3206. DOI: 10.1021/ol400912v) by Yuhong Zhang at Lanzhou University.