Carbon-Carbon Bond Construction: The Baran Synthesis of (+)-Chromazonarol
Daniel J. Weix of the University of Rochester effected (Org. Lett. 2012, 14, 1476. ) the in situ reductive coupling of an alkyl halide 2 with an acid chloride 1 to deliver the ketone 3. André B. Charette of the Université de Montréal (not illustrated) developed (Nature Chem. 2012, 4, 228. ) an alternative route to ketones by the coupling of an organometallic with an in situ activated secondary amide. Mahbub Alam and Christopher Wise of the Merck, Sharpe and Dohme UK chemical process group optimized (Org. Process Res. Dev. 2012, 16, 453. ) the opening of an epoxide 4 with a Grignard reagent 5. Ling Song of the Fujian Institute of Research on the Structure of Matter optimized (J. Org. Chem. 2012, 77, 4645. ) conditions for the 1,2-addition of a Grignard reagent (not illustrated) to a readily-enolizable ketone.
Wei-Wei Liao of Jilin University conceived (Org. Lett. 2012, 14, 2354. ) of an elegant assembly of highly functionalized quaternary centers, as illustrated by the conversion of 7 to 8. Antonio Rosales of the University of Granada and Ignacio Rodríguez-García of the University of Almería prepared (J. Org. Chem. 2012, 77, 4171. ) free radicals by reduction of an ozonide 9 in the presence of catalyic titanocene dichloride. In the absence of the acceptor 10, the dimer of the radical was obtained, presenting a simple alternative to the classic Kolbe coupling.
Marc L. Snapper of Boston College found (Eur. J. Org. Chem. 2012, 2308. ) that the difficult ketone 12 could be methylenated following a modifed Peterson protocol. Yoshito Kishi of Harvard University optimized (Org. Lett. 2012, 14, 86. ) the coupling of 15 with 16 to give 17. Masaharu Nakamura of Kyoto University devised (J. Org. Chem. 2012, 77, 1168. ) an iron catalyst for the coupling of 18 with 19.
The specific preparation of trisubsituted alkenes is an ongoing challenge. Quanri Wang of Fudan University and Andreas Goeke of Givaudan Shanghai fragmented (Angew. Chem. Int. Ed. 2012, 51, 5647. ) the ketone 21 by exposure to 22, to give the macrolide 23 with high stereocontrol.
Fernando López of CSIC Madrid and José L. Mascareñas of the Universidad Santiago de Compostela developed (Org. Lett. 2012, 14, 2996. ) a Pd catalyst for the conjugate addition of an alkyne 25 to an enone 24. Yong-Min Liang of Lanzhou University constructed (Angew. Chem. Int. Ed. 2012, 51, 1370. ) the highly functionalized quaternary center of 29 by combining the diazo ester 28 with the ester 27. Mariappan Pariasamy of the University of Hyderabad effected (Org. Lett. 2012, 14, 2932. ) enantioselective assembly of the allene 33 by combining 30 and 31 in the presence of the recyclable chiral auxiliary 32. Gojko Lalic of the University of Washington prepared (Org. Lett. 2012, 14, 362. ) the trisubstituted allene 36 by coupling 34 with 35.
Phil S. Baran of Scripps La Jolla prepared (J. Am. Chem. Soc. 2012, 134, 8432. ) the crystalline borane 38 by hydroboration of 37. Coupling with benzoquinone delivered the meroterpenoid (+)-Chromazonarol (39).