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Monday, March 19, 2012
Douglass F. Taber
University of Delaware

C-H Functionalization: The Ono/Kato/Dairi Synthesis of Fusiocca-1,10(14)-diene-3,8β,16-triol

Theodore A. Betley of Harvard University devised (J. Am. Chem. Soc. 2011, 133, 4917. DOI: 10.1021/ja110066j) an iron catalyst for inserting the nitrene from 2 in to the C-H of 1 to give 3. Bernhard Breit of the Freiburg Institute for Advanced Studies uncovered (J. Am. Chem. Soc. 2011, 133, 2386. DOI: 10.1021/ja1108613) a Rh catalyst that effected the intriguing hydration of a terminal alkyne 4 to the allylic ester 5. Yian Shi of Colorado State University specifically oxidized (Org. Lett. 2011, 13, 1548. DOI: 10.1021/ol200261a) one of the two allylic sites of 6, to give 7. Kálmán J. Szabó of Stockholm University optimized (J. Org. Chem. 2011, 76, 1503. DOI: 10.1021/jo1024199) the allylic oxidation of 9 to 10, using the inexpensive sodium perborate.

Masayuki Inoue of the University of Tokyo specifically carbamoylated (Tetrahedron Lett. 2011, 52, 2885. DOI: 10.1016/j.tetlet.2011.03.128) the acetonide 12 to give 14. Stephen Caddick of University College London added (Tetrahedron Lett. 2011, 52, 1067. DOI: 10.1016/j.tetlet.2010.12.083) the formyl radical from 15 to 16 to give 17. Ilhyong Ryu of Osaka Prefecture University and Maurizio Fagnoni of the University of Pavia employed (Angew. Chem. Int. Ed. 2011, 50, 1869. DOI: 10.1002/anie.201004854) a related strategy to effect the net transformation of 18 to 20.

There are many examples of the oxidation of ethers and amines to reactive intermediates that can go on to carbon-carbon bond formation. Ram A. Vishwakarma of the Indian Institute of Integrative Medicine observed (Chem. Commun. 2011, 47, 5852. DOI: 10.1039/C1CC11094B) that with an iron catalyst, the aryl Grignard 22 smoothly coupled with THF 21 to give 23. Gong Chen of Pennsylvania State University effected (Angew. Chem. Int. Ed. 2011, 50, 5192. DOI: 10.1002/anie.201100984) specific remote C-H arylation of 24, leading to 26. Takahiko Akiyama of Gakushuin University established (J. Am. Chem. Soc. 2011, 133, 2424. DOI: 10.1021/ja110520p) conditions for intramolecular hydride abstraction, effecting the conversion of 27 to 28.

C-H functionalization in nature is often mediated by cytochrome P450 oxidation. Zhi Li of the National University of Singapore showed (Chem. Commun. 2011, 47, 3284. DOI: 10.1039/C0CC04706F) that a particular cytochrome P450 selectively oxidized 29 to the alcohol 30, leaving the chemically more reactive benzylic position intact. Yoshihito Watanabe of Nagoya University (Angew. Chem. Int. Ed. 2011, 50, 5315. DOI: 10.1002/anie.201007975) and Manfred T. Reetz of the Max-Planck-Institut Mülheim (Angew. Chem. Int. Ed. 2011, 50, 2720. DOI: 10.1002/anie.201006587) independently established that in the presence of long chain perfluoro acids, a P450 could be induced to accept a low molecular weight hydrocarbon, as illustrated by the oxidation of 31 to 32.

Harnessing the enzymes of natural product synthesis is an ongoing objective. Yusuke Ono and Tohru Dairi of Hokkaido University and Nobuo Kato of Osaka University found (J. Am. Chem. Soc. 2011, 133, 2548. DOI: 10.1021/ja107785u) that an enzyme derived from the cloned gene cluster of Alternaria brassicicola effected the specific oxidation of 33 to Fusiocca-1,10(14)-diene-3,8β,16-triol (34).

D. F. Taber, Org. Chem. Highlights 2012, March 19.