Organic Chemistry Portal
Organic Chemistry Highlights

Monday, September 11, 2017
Douglass F. Taber
University of Delaware

Reactions of Alkenes: The Li Synthesis of Aflavazole

Koji Nemoto of AIST generated (Tetrahedron Lett. 2016, 57, 3199. DOI: 10.1016/j.tetlet.2016.06.036) a Ni catalyst in situ for the hydrocyanation of 1 to 3, using the inexpensive 2 as the HCN donor. Cancheng Guo of Hunan University oxidized (Tetrahedron Lett. 2016, 57, 80. DOI: 10.1016/j.tetlet.2015.11.064) the alkene 4 to the nitro alkene 5. Donald A. Watson of the University of Delaware prepared (Chem. Eur. J. 2016, 22, 15654. DOI: 10.1002/chem.201603677) the amide 8 by coupling the boronate 6 with the primary amide 7. Georgii I. Nikonov of Brock University showed (ACS Catal. 2016, 6, 7350. DOI: 10.1021/acscatal.6b01694) that the hydrosilylation of 9 proceeded with high diastereocontrol to give 10. Douglas W. Stephan of the University of Toronto demonstrated (Chem. Commun. 2016, 52, 8291. DOI: 10.1039/C6CC03970G) that a stable carbocation could catalyze the addition of benzyl mercaptan to the alkene 11, leading to 12.

Xian-Jin Yang of the East China University of Technology devised (Eur. J. Org. Chem. 2016, 4526. DOI: 10.1002/ejoc.201600709) conditions for converting 13 to the halo amide 14. Prodeep Phukan of Gauhati University reported (J. Org. Chem. 2016, 81, 5423. DOI: 10.1021/acs.joc.6b00785) a protocol (not illustrated) for converting an alkene to the complementary regioisomer of the halo amide.

Yian Shi of Colorado State University developed (J. Am. Chem. Soc. 2016, 138, 14864, DOI: 10.1021/jacs.6b10297; Org. Chem. Front. 2016, 3, 1131, DOI: 10.1039/C6QO00187D) a procedure for the hydroformylation of 4 to 15 using formic acid as the source of carbon monoxide. The reaction can be directed toward either the aldehyde or the carboxylic acid. Yao Fu of the University of Science and Technology of China used (Chem. Eur. J. 2016, 22, 11161. DOI: 10.1002/chem.201602486) 17 to deliver an alkyl group to 16, leading to 18. Ryan A. Shenvi of Scripps/La Jolla established (J. Am. Chem. Soc. 2016, 138, 12779. DOI: 10.1021/jacs.6b08507) that a Ni catalyst could couple an aryl iodide 20 with an alkene 19 to give 21. Magnus Rueping of RWTH Aachen University used (ACS Catal. 2016, 6, 4438. DOI: 10.1021/acscatal.6b00801) a Ni catalyst to couple an alkyl borane 22 with an aryl pivalate 23 to give 24. Jieping Zhu of the Ecole Polytechnique Fédérale de Lausanne added (Angew. Chem. Int. Ed. 2016, 55, 9249. DOI: 10.1002/anie.201604528) acetonitrile to the alkene 25 to give, after hydrolysis, the lactone 26. Longer chain nitriles worked as well.

Chen Zhu of Soochow University observed (Angew. Chem. Int. Ed. 2016, 55, 10821. DOI: 10.1002/anie.201605130) that under free radical conditions, the cyanohydrin of 27 could serve as a nitrile donor. The result was the elegant conversion of 27 to 28 with both regio- and diastereocontrol.

Aflavazole (31) is an antiinsectan carbazole isolated from Aspergillus flavus. En route to 31, Ang Li of the Shanghai Institute of Organic Chemistry reduced (J. Am. Chem. Soc. 2016, 138, 15555. DOI: 10.1021/jacs.6b10880) the methylene of 29 stereoselectively to the axial methyl group of 30.

D. F. Taber, Org. Chem. Highlights 2017, September 11.