New Methods for Carbocyclic Construction: The Kim Synthesis of Pentalenene

Daesung Lee of the University of Illinois, Chicago, taking advantage of the facile insertion of an alkylidene carbene into a C-Si bond, established (J. Am. Chem. Soc. 2010, 132, 6640) a general method for the conversion of an α-silyl ketone 1 into the silyl cyclopropene 3. Christopher D. Bray of Queen Mary University showed (J. Org. Chem. 2010, 75, 4652) that the sulfonyl phosphonate 5 converted the enantiomerically pure epoxide 4 into the cyclopropane 6. Paul Margaretha of the University of Hamburg observed (Organic Lett. 2010, 12, 728) smooth photochemical combination of 7 and 8 to give 9 with high diastereocontrol. Tõnis Kanger of the Tallinn University of Technology devised (Organic Lett. 2010, 12, 2230) the three-component coupling of 10, 11, and diethyl amine to give, after reduction, the highly substituted cyclobutane 12. Min Shi of the Shanghai Institute of Organic Chemistry uncovered (J. Org. Chem. 2010, 75, 902) an interesting new thermal rearrangement: the conversion of 13 to 14. José G. Ávila-Zárraga of the Universidad Nacional Autónoma de México applied (Tetrahedron Lett. 2010, 51, 2232) Pd catalysis to the cyclization of the epoxy nitrile 15, redirecting the reaction from the expected cyclobutane to the cyclopentanol 16. Ullrich Jahn of the Academy of Sciences of the Czech Republic effected (J. Org. Chem. 2010, 75, 4480) the oxidative radical cyclization of 17 to 18. Initial deprotonation of the substrate with t -BuMgCl switched the product to the trans diastereomer. Jonathan W. Burton of the University of Oxford employed (Organic Lett. 2010, 12, 2738) a related oxidative cyclization for the diastereoselective conversion of 19 to 20. E. J. Corey of Harvard University reported (Organic Lett. 2010, 12, 300) a new ligand for the enantioselective Ni-mediated reduction of 21 to 22. Shu-Li You, also of the Shanghai Institute of Organic Chemistry, established (J. Am. Chem. Soc. 2010, 132, 4056) that the alcohol 23, readily prepared by oxidation of p -cresol, could be cyclized to the crystalline 25 in high ee.

Stereocontrolled Carbocyclic Construction: The Mulzer Synthesis of (-)-Penifulvin A

Tanmaya Pathak of the Indian Institute of Technology, Kharagpur devised (J. Org. Chem. 2009, 74, 2710) a preparation of enantiomerically-pure oxygenated cyclopropanes such as 3 from carbohydrate precursors. Andrei K. Yudin of the University of Toronto established (Organic Lett. 2009, 11, 1281) a route to aminated cyclobutanes such as 5 based on sigmatropic rearrangement of the β-lactam 4. Tanmaya Pathak of the Indian Institute of Technology, Kharagpur devised ( J. Org. Chem. 2009 , 74 , 2710) a preparation of enantiomerically-pure oxygenated cyclopropanes such as 3 from carbohydrate precursors. Andrei K. Yudin of the University of Toronto established (Organic Lett . 2009 , 11 , 1281) a route to aminated cyclobutanes such as 5 based on sigmatropic rearrangement of the β -lactam 4 . Stephen C. Bergmeier of Ohio University reported (Tetrahedron 2009, 65, 741) a study of the balance between five- and six-membered ring formation in the cyclization of aziridines such as 6. Professor Bergmeier also described (Tetrahedron Lett. 2009, 50, 1261) the bridging additions of enones to cyclic allyl silanes such as 8. This is particularly interesting, as 8 is easily prepared by Birch reduction of the corresponding phenyl silane. Ullrich Jahn of the Academy of Sciences of the Czech Republic observed (Chem. Eur. J. 2009, 15, 58) that the free-radical cyclization of 11 proceeded to give mainly the diastereomer 12 (~ 1:1 at the secondary allylic position). Daesung Lee of the University of Illinois at Chicago reasoned (J. Am. Chem. Soc. 2009, 131, 8413) that the stereochemical relationship between the O and the adjacent C-H of 13 was such that the C-H would be deactivated. The cyclization of the alkylidene carbene derived from 13 indeed proceeded to give 14, setting the stage for the synthesis of platensimycin. Marco A. Cufolini of the University of British Columbia found (Organic Lett . 2009, 11, 1539) an easy protocol for the generation of a nitrile oxide and subsequent dipolar cycloaddition, by oxidation of the oxime.