Practical enantioselective Diels-Alder and aldol reactions using a new chiral controller system

Abstract

of activation suggests that N2 loss from 4 to give 5 is not a concerted process and probably involves a rate-determining ligand rearrangement (perhaps ring expansion with formation of a Zr-0 bond) before N2 extrusion occurs, 5 is reactive toward a number of other small molecules, and elaboration of this reaction chemistry will be the topic of a future publication.Acknowledgment. Financial support from the National Science Foundation (CHE-8818607) and an Alfred P. Sloan Foundation Research Fellowship (1989-1991 is sincerely appreciated by G.L.H. A summer fellowship under the N.S.F. Research Experiences for Undergraduates Program (NSF 8713014) is gratefully acknowledged by C.D.S. The NMR facilities were supported in part through the University of Chicago Cancer Center Grant (NIH-CA-14599).Supplementary Material Available: Experimental, spectroscopic ( , l3C NMR, and IR), analytical, and crystallographic details and tables of atomic coordinates, bond angles and distances,

The Chemistry of Vicinal Diamines

“…Diastereomeric aminals also allow the determination of the enantiomeric composition of chiral aldehydes and substituted cycloalkanones, either by NMR spectroscopy or by a chromatographic technique (HPLC or GC). [19a, b] Alexakis et al then introduced phosphorus derivatives such as 28, which were obtained from C 2 -symmetric diamines, for the determination of the enantiomeric composition of chiral alcohols, thiols, and amines by 31 [19f] were also employed for such a purpose by other authors.…”

“…As shown in Scheme 11, syn-aldol products (57) were also obtained with high diastereomeric and enantiomeric excesses from diethyl ketone (55), in reactions mediated by the boron reagent 56. [31] The allylborane derivative 58 (Scheme 12) was shown to be an excellent reagent for the enantioselective allylation of aldehydes (ee 95 ± 98 %). The adducts 59 are useful pre- cursors of b-hydroxy-and g-hydroxycarboxylic acid derivatives.…”

Generation and cycloaddition of semi-stabilized 2-azaallyllithiums via electrocyclic ring-opening or cycloreversion reactions

“…Nonetheless, this experiment showed that diamines may be used as starting materials for 2-azaallyl anion chemistry. To avoid the dimerization of the imine by-product of the imidazolidine cycloreversion, we synthesized the N-isopropyl diamine 37 from (d,l-)-stilbenediamine 35 20 by a reductive amination approach (Scheme 10). We hoped that imidazolidines derived from 37 would form N- benzylidineisopropylamine as a by-product, which might not dimerize, owing to steric considerations.…”

The Influence of Ligand Side Chain on the Enantioselectivity of Lewis Acid Catalyzed Diels-Alder Reactions.

“…1). In order to test the influence of the side chain at 2-position of chiral oxazolines, we examined the Lewis acid-catalyzed Diels-Alder reactions of well-used 3-(2-propenoyl)-1,3-oxazolidin-2-one 8 [18][19][20][21][22] as a dienophile with cyclopentadiene using moxes 2-6 as chiral ligands.…”