Alkenes effect

Mechanistically related to Mn, is the use of Fe as an epoxidation catalyst. Recently, iron complexes with a tetradentate amine core were reported, that were capable of activating H202 without the involvement of hydroxyl radicals [72]. For a variety of substituted as well as terminal alkenes, effective epoxidation... 

Application of Various Chiral Reagents Derived from IpciBH. Diisopinocampheylborane does not normally yield satisfactory ee s in hydroboration reactions of 1,1-disubstituted alkenes, /rans-alkenes, or trisubstituted alkenes. This problem has been partially solved by the introduction of Monoisopinocam-pheylborane, IpcBHa, which is derived from IPC2BH. IpcBH2 handles frans -alkenes and trisubstituted alkenes effectively, since... 

Mechanism Formation of (E)-alkenes (E)-Selectivity, effect of phosphonate size Formation of (Z)-alkenes Effect of bases... 

Tertiary amines. Using a secondary amine to decompose an ozonide derived from 1-alkene effects its alkylation. The amine initiates an eliminative fragmentation of the ozonide to generate an aldehyde and dialkylammonium formate. Schiff base formation from the aldehyde and another molecule of the amine is then followed by reduction by the formate ion. 

In both epoxidation examples, the stereoselectivity is due to the cyclic nature of the transition state the fact that there is a hydrogen bond or O-metal bond delivering the reagent to one face of the alkene. Effectively we have moved on from the tethered nucleophiles of the last section to (transiently) tethered reagents. This is a very important concept, and we revisit it in the next chapter cyclic transition states are the key to getting good stereoselectivity in reactions of acyclic compounds. 

Frontier molecular orbital analysis validates the proposed transition state 133, where the predisposed arrangement of the enamine secures a favorable interaction between C-N c and n of alkene effectively lowering the LUMO energy of this conformation. ... 

Lately, Kuwano and coworkers reported on the 1,2-migration in the rhodium catalyzed reaction of alkenyl acetates and arylboron reagents, producing the isomerized frani-alkenes effectively. The catalytic system proved less sensitive to the steric interactions of the Cl substituent resulting in a broad scope and good regioselectivities (Scheme 2.5) [16]. 

Cossu S, Peluso P, Alberico E, Marchetti M. Rhodium catalyzed hydroformylation of 2-phenylsulfonylbicyclo[2.2.1] alkenes effect of the phenylsulfonyl group. Tetrahedron Lett. 2006 47 2569-2572. 

---