• CAS Science Spotlight Home
• Most Requested Documents 3Q02-Chemistry and Related
• About
• What's New

Home   •   Spotlight  •  rlist3q02  •  Most Requested Documents 3Q02-Chemistry and Related (10)

Most Requested Documents 3Q02-Chemistry and Related

Following is one of the documents most requested by researchers using CAS electronic products.

---

CAS indexed 181 chemical substances from this document. CAS subject entries for this document include: Ketones, preparation; Oxidation kinetics; Chemoselectivity; and 5 additional concepts.

CAPLUS COPYRIGHT 2002 ACS

TITLE:	Iodine(V) Reagents in Organic Synthesis. Part 4. o-Iodoxybenzoic Acid as a Chemospecific Tool for Single Electron Transfer-Based Oxidation Processes
AUTHOR(S):	Nicolaou, K. C.; Montagnon, T.; Baran, P. S.; Zhong, Y.-L.
CORPORATE SOURCE:	Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
SOURCE:	Journal of the American Chemical Society (2002), 124(10), 2245-2258 CODEN: JACSAT; ISSN: 0002-7863
PUBLISHER:	American Chemical Society
LANGUAGE:	English

ABSTRACT:
Cyclic and acyclic ketones undergo selective oxidn. with the hypervalent iodine reagents o-iodoxybenzoic acid (IBX) to give .alpha.,.beta.-unsatd. carbonyl compds. Depending on the no. of equiv. of IBX present, cyclic and acyclic ketones can be selectively oxidized to give either the mono-.alpha.,.beta.-unsatd. or the bisunsatd. dienones. Primary and secondary alcs. may also be oxidized selectively to either ketones and aldehydes or .alpha.,.beta.-unsatd. carbonyl compds. IBX was used as a selective oxidant in the expeditious prepns. of cyclohepta-2,6-dien-1-one, tropinone, and a [3.3.1]azabicyclononane analog of tropinone. Medium- and large-ring unsatd. ketones can also be prepd. stereoselectively from te corresponding ketones by treatment with IBX; the stereoselectivity varies with ring size. Ring-opened products isolated from the oxidn. of a diphenylcyclopropylacetaldehyde and Hammett correlations of the oxidns. of 1,2-diaryl-1-propanones support the presence of radical intermdiates in the oxidns. and suggest a single electron transfer mechanism for the oxidn. of ketones with IBX. Arenes can also be selectively oxidized to aryl aldehydes and ketones in the presence of IBX. Only arenes with open ortho-positions undergo benzylic oxidn. with IBX. Electron-deficient arenes do not undergo benzylic oxidn. with IBX; arenes possessing alkoxy substituents undergo oxidn. more slowly than arenes with other substituents. Aryl monoaldehydes and monoketones can be selectively prepd. by oxidn. of sym. arenes. Hammett correlations of 4-substituted toluenes and their oxidns. with IBX were performed to study the mechanism of benzylic oxidn. of arenes with IBX. The rate of IBX-mediated oxidn. of ketones occurs much more rapidly than the oxidn. of benzylic positions by IBX. The relative rates of benzylic oxidn. and of IBX-mediated radical cyclization can be tuned by changing the solvents; in DMSO alone, benzylic oxidn. occurs readily, while in a 10:1 mixt. of THF and DMSO, radical cyclization is preferred. In the presence of an acid promoter, IBX-mediated oxidn. of ketones and aldehydes to their .alpha.,.beta.-unsatd. counterparts is preferred to radical cyclization in a multifunctional substrate.

View full-text pdf document from the American Chemical Society, a participating ChemPort publisher.