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Monday, September 9, 2013
Tristan H. Lambert
Columbia University

Synthesis and Reactions of Alkenes

Christine L. Willis and Varinder K. Aggarwal at the University of Bristol have developed (Angew. Chem. Int. Ed. 2012, 51, 12444. ) a procedure for the diastereodivergent synthesis of trisubstituted alkenes via the protodeboronation of allylic boronates, such as in the conversion of 1 to either 2 or 3. An alternative approach to the stereoselective synthesis of trisubstituted alkenes involving the reduction of the allylic C-O bond of cyclic allylic ethers (e.g 4 to 5) was reported (Chem. Commun. 2012, 48, 7844. ) by Jon T. Njardarson at the University of Arizona.

A novel synthesis of allylamines was developed (J. Am. Chem. Soc. 2012, 134, 20613. ) by Hanmin Huang at the Chinese Academy of Sciences with the Pd(II)-catalyzed vinylation of styrenes with aminals (e.g. 6 + 7 to 8). Eun Jin Cho at Hanyang University showed (J. Org. Chem. 2012, 77, 11383. ) that alkenes such as 9 could be trifluoromethylated with iodotrifluoromethane under visible light photoredox catalysis.

David A. Nicewicz at the University of North Carolina at Chapel Hill developed (J. Am. Chem. Soc. 2012, 134, 18577. ) a photoredox procedure for the anti-Markovnikov hydroetherification of alkenols such as 11, using the acridinium salt 12 in the presence of phenylmalononitrile (13). A unique example of "catalysis through temporary intramolecularity" was reported (J. Am. Chem. Soc. 2012, 134, 16571. ) by André M. Beauchemin at the University of Ottawa with the formaldehyde-catalyzed Cope-type hydroamination of allyl amine 15 to produce the diamine 16.

A free radical hydrofluorination of unactivated alkenes, including those bearing complex functionality such as 17, was developed (J. Am. Chem. Soc. 2012, 134, 13588. ) by Dale L. Boger at Scripps, La Jolla. Jennifer M. Schomaker at the University of Wisconsin at Madison reported (J. Am. Chem. Soc. 2012, 134, 16131. ) the copper-catalyzed conversion of bromostyrene 19 to 20 in what was termed an activating group recycling strategy.

A rhodium complex 23 that incorporates a new chiral cyclopentadienyl ligand was developed (Science 2012, 338, 504. ) by Nicolai Cramer at the Swiss Federal Institute of Technology in Lausanne and shown to promote the enantioselective merger of hydroxamic acid derivative 21 and styrene 22 to produce 24. Vy M. Dong at UC-Irvine reported (J. Am. Chem. Soc. 2012, 134, 15022. ) a catalyst system that allowed for the hydroacylation of unactivated alkenes such as 26 with salicaldehyde 25 with high linear to branched selectivities.

F. Dean Toste at UC-Berkeley found (Angew. Chem. Int. Ed. 2012, 51, 8082. ) that an oxorhenium compound was a superior catalyst for the deoxygenation of polyols to form alkenes, such as with the conversion of D-sorbitol (28) to 1,3,5-hexatriene (29). Our group reported (J. Am. Chem. Soc. 2012, 134, 18581. ) the organocatalytic ring-opening carbonyl-olefin metathesis of cyclopropene 31 with benzaldehyde (30) to produce enal 33, using the simple bicyclic hydrazine catalyst 32.

Lastly, the synthesis of the longest conjugated polyene 36 yet prepared, was reported (Org. Lett. 2012, 14, 5496. ) by Hans-Richard Sliwka at the Norwegian University of Science and Technology and Ana Martínez at the National Autonomous University of Mexico by way of a microwave-assisted double Wittig reaction of dialdehyde 35 and phosphonium salt 34.

T. H. Lambert, Org. Chem. Highlights 2013, September 9.