Selective Reactions of Alkenes

Fabio Doctorovich of the Universidad de Buenos Aires reported (/. Org. Chem. 2008, 73, 5379) that hydroxylamme in the presence of an Fe catalyst reduced alkenes such as 1, but not ketones or esters. Erick Carreira of ETH Zurich developed (Angew. Chem. Int. Ed. 2008, 47, 5758) mild conditions for the hydrochlorination of mono-, di- and trisubstituted alkenes. Ramgopal Bhattacharyya of ladavpur University established Tetrahedron Lett. 2008, 49, 6205) a simple Mo-catalyzed protocol for alkene epoxidation. 

Nitro alkenes are of increasing importance as acceptors for enantioselective organocata-lyzed carbon-carbon bond formation. Matthias Beller of the Universitat Rostock found Adv. Synth. Cat. 2008, 350, 2493) that an alkene such as 7 was readily converted to the corresponding nitroalkene 8 by exposure to of NO gas. The reaction could also be effected withNaNOj/HOAC. 

Several other methods for the functionalizing homologation of alkenes have been pul forward. Chul-Ho lun of Yonsei University assembled (J. Org. Chem. 2008, 73, 5598) a Rh catalyst that effected the oxidative acylation of a terminal alkene 13 with a primary benzylic alcohol, to give the ketone 14. For now, this approach is Umiled to less expensive alkenes, as the alkene, used in excess, is the reductant in the reaction. The other procedures outlined here require only stoichiometric alkene. Yasuhiro Shiraishi of Osaka University devised Organic Lett. 2008, 10, 3117) a simple photoprocess for adding acetone to a 

Continuing the investigation of tandem Ru-catalyzed reactions, Marc L. Snapper of Boston College effected Organic Lett. 2007, 9, 1749) metathesis with methacrolein 8a, then added Ph P and diazoacetate, to give the diene 11. A range of common Ru catalysts worked well for this transformation. In an alternative approach to trisubstituted alkene 

The construction of tetrasubstituted alkenes has been more challenging. Yaim Schrodi of Materia, Inc. (Organic Lett. 2007, 9,1589) has described a catalyst 17 that is particularly effective. Complex 17 was superior to a catalyst reported (Organic Lett. 2007, 9, 1339) shortly earher by Robert H. Grubbs of Caltech. 

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The presence of solids such as clays, zeolites, silica or ion-exchange resins may allow catalysis or control of organic reactions. Often, yields are higher and work-up procedures simpler than for the corresponding homogeneous reactions, and product distributions may also be improved. Examples of selective substitution reactions in aromatic and heteroaromatic systems and of selective reactions of alkenes are discussed, and the wider potential for synthesis of fine chemicals is discussed. 

Alkynes react slower with ozone than do alkenes and selective reaction of alkenes can be achieved in the presence of alkynes (eq 17). Conversely, the example of eq 18 shows that alkynes are more reactive toward ozone than aromatic rings. ... 

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