Monday, September 14, 2015
Douglass F. Taber
University of Delaware
C-H Functionalization: The Shaw Synthesis of E-δ-Viniferin
Thomas Lectka of Johns Hopkins University reported (J. Org. Chem. 2014, 79, 8895. ) a simple protocol for free radical monofluorination, exemplified by the conversion of 1 to 2. Michael K. Hilinski of the University of Virginia used (Org. Lett. 2014, 16, 6504. ) a catalytic amount of the ketone 4 to mediate the oxidation of 3 to diol 5. Oxidation of 3 with DMDO gave the regioisomeric tertiary alcohol (not illustrated).
Jeung Gon Kim and Sukbok Chang of KAIST used (Chem. Commun 2014, 50, 12073. ) an Ir catalyst to convert 6 selectively to the primary sulfonamide 7. Paul J. Chirik of Princeton University employed (J. Am. Chem. Soc. 2014, 136, 12108. ) a Co catalyst to effect the migration of the internal alkene of 8 to the terminal alkene, that then underwent dehydrogenative silylation to deliver the allyl silane 10.
Jiang Cheng of Changzhou University developed (J. Org. Chem. 2014, 79, 9847. ) conditions for the aminoalkylation of cyclohexane 11 to 13. Ilhyong Ryu of Osaka Prefecture University and Maurizio Fagnoni of the University of Pavia observed (Chem. Sci. 2014, 5, 2893. ) high selectivity in the addition of 14 to 15. Of the five possible regioisomers, 16 dominated.
In another light-mediated transformation, Shin Kamijo of Yamaguchi University and Masayuki Inoue of the University of Tokyo added (Chem. Sci. 2014, 5, 4339. ) 17 to 18 to give 19. Huw M. L. Davies of Emory University established (J. Am. Chem. Soc. 2014, 136, 17718. ) conditions for the enantioselective alkylation of a methyl ether 21 with 20 to give the ester 22. Selective methyl insertion was observed even with much more complex substrates. The trichloroethyl ester was critical for this transformation.
James A. Bull of Imperial College London effected (Org. Lett. 2014, 16, 4956. ) selective cis-arylation of the proline-derived amide 23 with 24 to give 25. E. Peter Kündig of the University of Geneva coupled (Chem. Eur. J. 2014, 20, 15021. ) the amine 27 with 26, then cyclized that product to the indoline 28. The enantiomeric Pd catalyst delivered the regioisomeric C-H insertion product. Jieping Zhu of the Ecole Polytechnique Fédérale de Lausanne observed (Angew. Chem. Int. Ed. 2014, 53, 1818. ) the efficient cyclization of 29 to 30. Chi-Ming Che of the University of Hong Kong converted (Angew. Chem. Int. Ed. 2014, 53, 14175. ) the ketone of 31 into the dialkyl diazo compound in situ, then used a Ru catalyst to cyclize that with high diastereocontrol to 32.
The reversatrol dimer E-δ-Viniferin (35) is induced in grapes by fungal infection. En route to 35, Jared T. Shaw of UC Davis oxidized (J. Am. Chem. Soc. 2014, 136, 15142. ) the hydrazone of 33 to the diaryl diazo intermediate, then cyclized that with a Rh catalyst to 34 in high ee.
D. F. Taber, Org. Chem. Highlights 2015, September 14.