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Monday, June 13, 2011
Douglass F. Taber
University of Delaware

Substituted Benzenes: The Kirsch Synthesis of Cybrodol

Stephen L. Buchwald of MIT established (J. Am. Chem. Soc. 2010, 132, 14076. ) a Pd-catalyzed protocol for conversion of an aryl triflate 1 to the halide 2. Jie Wu of Fudan University prepared (Tetrahedron Lett. 2010, 51, 6646. ) aromatic halides from the corresponding carboxylic acids.

Yong-Chua Teo of Nanyang Technological University described (Tetrahedron Lett. 2010, 51, 3910. ) the Mn-mediated conversion of 3 to 5, suggesting a benzyne intermediate. Takanori Shibata of Waseda University effected (Synlett 2010, 2601. ) the direct Ru-mediated coupling of aryl halides with amines, and Paul Helquist of the University of Notre Dame prepared (J. Org. Chem. 2010, 75, 4887. ) anilines by coupling aryl halides with NaN3.

Chao-Jun Li of McGill University devised (Tetrahedron Lett. 2010, 51, 5486. ) the Pd-catalyzed decarbonylative Heck coupling of 6 with 7 to give 8. Mats Larhed of Uppsala University showed (Angew. Chem. Int. Ed. 2010, 49, 7733. ) that Pd could also catalyze the decarboxylative coupling of an aromatic acid 9 with a nitrile to give the ketone 10.

Dennis G. Hall of the University of Alberta found (Tetrahedron Lett. 2010, 51, 4256. ) that an areneboronic acid could promote the Zr-catalyzed ortho condensation of a phenol 11 with an aldehyde, leading to 12, that could then be carried on to a range of other products. Professor Hall also showed (Angew. Chem. Int. Ed. 2010, 49, 2883. ) that areneboronic acids are stable to many standard organic transformations, and that the product boronic acids can be readily purified by extraction into sorbitol/Na2CO3. Professor Buchwald reported (J. Am. Chem. Soc. 2010, 132, 14073. ) an optimized source of Pd for the Suzuki-Miyaura coupling, allowing the room temperature participation even of unstable boronic acids such as 13.

Wing-Yiu Yu of the Hong Kong Polytechnic University observed (J. Am. Chem. Soc. 2010, 132, 12862. ) that 17 was an effective donor for the Pd-catalyzed ortho C-H amination of 16. Nicholas C. O. Tomkinson of Cardiff University uncovered (Synlett 2010, 2471. ) the facile rearrangement of 19 to 20.

Professor Buchwald described (J. Am. Chem. Soc. 2010, 132, 9990. ) the coupling of 21, prepared from the aryl halide, with 22 to give the benzofuran 23. Professor Yu devised (Org. Lett. 2010, 12, 3926. ) the Pd-catalyzed ortho C-H coupling of 24 with an aldehyde 25 to give the ketone 26.

For highly-substituted benzene derivatives, it is sometimes more effective to construct the benzene ring. In the course of a synthesis of Cybrodol (29), Stefan F. Kirsch of the Technische Universität München cyclized (Angew. Chem. Int. Ed. 2010, 49, 4661. ) the alkyne 27 to 28 with N-iodosuccinimide.

D. F. Taber, Org. Chem. Highlights 2011, June 13.