Academic literature on the topic 'Palladium-catalyzed cascade reactions'

The reduction of pyridines offers an attractive approach to piperidine synthesis, and now Toshimichi Ohmura and Michinori Suginome of Kyoto University have developed (J. Am. Chem. Soc. 2012, 134, 3699) a rhodium-catalyzed hydroboration of pyridines, including the reaction of 1 to produce 3. Timothy J. Donohoe at the University of Oxford has found (Org. Lett. 2011, 13, 2074) that pyridinium silanes 4 undergo intramolecular hydride transfer by treatment with TBAF to produce dihydropyridones (e.g., 5) with good diastereoselectivity. Enantioselective amination of allylic alcohols has proven challenging, but Ross A. Widenhoefer at Duke University has reported (Angew. Chem. Int. Ed. 2012, 51, 1405) that a chiral gold catalyst can effect such intramolecular cyclizations with good enantioselectivity, as in the synthesis of 7 from 6. Alternatively, Masato Kitamura at Nagoya University has developed (Org. Lett. 2012, 14, 608) a ruthenium catalyst that operates at as low as 0.05 mol% loading for the conversion of substrates such as 8 to 9. Efforts to replace transition metal catalysts with alkaline earth metal-based alternatives have been gaining increasing attention, and Kai C. Hultzsch at Rutgers University has found (Angew. Chem. Int. Ed. 2012, 51, 394) that the magnesium complex 12 is capable of catalyzing intramolecular hydroamination (e.g., 10 to 11) with high enantioselectivity. Meanwhile, a stereoselective Wacker-type oxidation of tert-butanesulfinamides such as 13 to produce pyrrolidine derivatives 14 has been disclosed (Org. Lett. 2012, 14, 1242) by Shannon S. Stahl at the University of Wisconsin at Madison. Though highly desirable, Heck reactions have rarely proven feasible with alkyl halides due to competitive β-hydride elimination of the alkyl palladium intermediates. Sherry R. Chemler at the State University of New York at Buffalo has demonstrated (J. Am. Chem. Soc. 2012, 134, 2020) a copper-catalyzed enantioselective amination Heck-type cascade (e.g., 15 and 16 to 17) that is thought to proceed via radical intermediates. David L. Van Vranken at the University of California at Irvine has reported (Org. Lett. 2012, 14, 3233) the carbenylative amination of N-tosylhydrazones, which proceeds through η3-allyl Pd intermediates constructed via carbene insertion. This chemistry was applied to the two-step synthesis of caulophyllumine B from vinyl iodide 18 and N-tosylhydrazone 19.

Benjamin List at the Max-Planck-Institute in Mülheim reported (Angew. Chem. Int. Ed. 2013, 52, 3490) that the chiral phosphoric acid TRIP catalyzed the asymmet­ric SN2-type intramolecular etherification of 1 to produce tetrahydrofuran 2 with a selectivity factor of 82. The coupling of alkenol 3 with 4 to give the α-arylated tetra­hydropyran 5 via a method that combined gold catalysis and photoredox catalysis was disclosed (J. Am. Chem. Soc. 2013, 135, 5505) by Frank Glorius at Westfälische Wilhelms-Universität Münster. Mark Lautens at the University of Toronto reported (Org. Lett. 2013, 15, 1148) the conversion of cyclohexanedione 6 and phenylboronic acid to bicyclic ether 8 using rhodium catalysis in the presence of dienyl ligand 7. Propargylic ether 9 was found (Org. Lett. 2013, 15, 2926) by John P. Wolfe at the University of Michigan to undergo conversion to furanone 10 upon treatment with dibutylboron triflate and Hünig’s base followed by oxidation with hydrogen peroxide. Tomislav Rovis at Colorado State University demonstrated (Chem. Sci. 2013, 4, 1668) that the spirocyclic compound 13 could be prepared in enantioenriched form from 11 by a photoisomerization- coupled Stetter reaction using carbene catalyst 12. Antonio C. B. Burtoloso at the University of São Paulo reported (Org. Lett. 2013, 15, 2434) the conversion of ketone 14 to lactone 15 using samarium(II) iodide and methyl acrylate. The merger of diketone 16 and pyrone 17 in the presence of Amberlyst-15 to pro­duce (−)- tenuipyrone 18 was disclosed (Org. Lett. 2013, 15, 6) by Rongbiao Tong at the Hong Kong University of Science and Technology. Joanne E. Harvey at Victoria University of Wellington in New Zealand found (Org. Lett. 2013, 15, 2430) that tricy­clic ether 20 could be generated efficiently from dihydropyran 19 and pyrone 17 via a palladium-catalyzed double allylic alkylation cascade. Two rings and four stereocenters were generated in the construction of bicyclic ether 23 from dienol 21 and acetal 22 via a Lewis acid-mediated cascade, as reported (Org. Lett. 2013, 15, 2046) by Christine L. Willis at the University of Bristol.