90809-23-7Relevant academic research and scientific papers
Synthesis of Optically Active Bifunctional Isoprenoid Building Blocks by Rhodium(I)-Catalyzed Asymmetric Allylamine to Enamine Isomerization
Schmid, Rudolf,Hansen, Hans-Juergen
, p. 1258 - 1275 (2007/10/02)
The application of the known asymmetric allylamine to enamine isomerization methodology to bifunctional C5-isoprenoid allylic amines of types IId and IIe (Scheme 1) is described.It is shown that a number of such substrates can be isomerized with enantioselectivities of >90percent ee using cationic RhI complexes containing (6,6'-dimethylbiphenyl-2,2'-diyl)bis(diphenylphosphine) (BIPHEMP; 9) as asymmetry-inducing ligand (Scheme 2, Tables 1 and 2).Synthetically most useful is the isomerization of the benzyloxy derivative 10a into the (E)-enamine 11a.This isomerization proceeds with very high enantioselectivity (98-99percent ee) and affords, after enamine hydrolysis, the optically active 4-(benzyloxy)-3-methylbutanals ((R)- or (S)-12) in chemical yields of ca. 90percent.In conjunction, a short synthetic route to the starting material 10a has been developed which has a Pd-catalyzed amination of isoprene epoxide (30) as the key step.Thus, convenient and practical access to the optically active aldehydes (R)- and (S)-12 is now at hand.These aldehydes are useful optically active bifunctional building blocks for isoprenoid homologation.
Phosphorus compounds
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, (2008/06/13)
Novel chiral phosphorus compounds of the general formula STR1 wherein R signifies substituted or unsubstituted phenyl, R1 and R2, which can be the same or different, signify hydrogen, lower alkyl, lower alkoxy, di-lower alkylamino or protected hydroxymethyl or R1 and R2 together signify the group STR2 in which m represents a number 3 to 5, R4 represents lower alkyl, substituted or unsubstituted phenyl or benzyl and R5 represents lower alkyl or both R5 's together represent lower alkylene, R3 signifies methyl, lower alkoxy, di-lower alkylamino or fluorine and n signifies the number 0, 1, 2 or 3, are described. The compounds of formula I are useful in the form of complexes with a metal of Group VIII as catalysts for asymmetric hydrogenations and enantioselective hydrogen displacements in prochiral allylic systems.
