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Monday, September 21, 2009
Douglass F. Taber
University of Delaware

Organic Functional Group Interconversion: (-)-β-Conhydrine (Barua) and (+)-6'-Hydroxyarenarol (Anderson)

V. T. Perchyonok and Kellie L. Tuck of Monash University found (Tetrahedron Lett. 2008, 49, 4777. ) that a concentrated solution of Bu4NCl and H3PO2 in water effected free radical reductions and cyclizations. Stéphane G. Ouellet of Merck Frosst demonstrated (Tetrahedron Lett. 2008, 49, 6707. ) that an oxazoline such as 3 could be converted to the alcohol 4 by acylation followed by reduction. Elizabeth R. Burkhardt of BASF developed (Tetrahedron Lett. 2008, 49, 5152. ) a protocol for scalable reductive amination using an easily metered liquid pyridine-borane complex. Mohammad Movassaghi of MIT devised (Angew. Chem. Int. Ed. 2008, 47, 8909. ) a strategy for conversion of an allylic carbonate 8 by way of the allylic diazene to the terminal alkene 9.

Philippe Compain of the Université d’Orleans uncovered (J. Org. Chem. 2008, 73, 8647. ) a practical procedure for oxidizing an inexpensive aldose such as 10 to the amide 12, a valuable chiral pool starting material. Karl A. Scheidt of Northwestern University extended (Org. Lett. 2008, 10, 4331. ) activated MnO2 oxidation to saturated aldehydes such as 13, leading to the ester 15. Tohru Fukuyama of the University of Tokyo showed (Org. Lett. 2008, 10, 2259. ) that halides such as 16 could be oxidized to the oxime 18 with the reagent 17. The product oximes are readily dehydrated to the corresponding nitriles. Chutima Kuhakarn of Mahidol University devised (Synthesis 2008, 2045. ) a simple protocol for the oxidation of a primary amine such as 19 to the nitrile 20.

Nasser Iranpoor and Habib Firouzabadi of Shiraz University developed (J. Org. Chem. 2008, 73, 4882. ) the reagent 22 for Mitsunobu coupling. The stereochemical course of this reaction with simple acyclic secondary alcohols such as 21 was not reported. Salvatore D. Lepore of Florida Atlantic University optimized (Angew. Chem. Int. Ed. 2008, 47, 7511. ) the quisylate 24 for the displacement with retention to give the azide 25. Hideki Yorimitsu and Koichiro Oshima of Kyoto University optimized (J. Am. Chem. Soc. 2008, 130, 11276. ) a Co catalyst for the conversion of a secondary halide such as 26 to the terminal alkene 27. Base-mediated elimination gave primarily the internal alkene. Christian E. Schafmeister of the University of Pennsylvania established (J. Am. Chem. Soc. 2008, 130, 14382. ) that acyl fluorides such as 28 couple efficiently even with unreactive amino acids such as 29.

In the course of a synthesis of (-)-β-conhydrine (33) (Tetrahedron Lett. 2008, 49, 6508. ), Nabin C. Barua of North East Institute of Science and Technology needed to reduce the nitro group of 31 to the amine without reducing the very reactive monosubstituted alkene. Zn/NH4Cl served well. James C. Anderson of the University of Nottingham solved (J. Org. Chem. 2008, 73, 8033. ) a similar problem in a synthesis of (+)-6'-hydroxyarenarol (36). In that case, Raney Ni reduced the carbon-sulfur bond without affecting the monosubstituted alkene.

D. F. Taber, Org. Chem. Highlights 2009, September 21.