-
[show abstract]
[hide abstract]
ABSTRACT: A series of novel C 1 symmetric thiazole ligands with a tetrahydroisoquinoline (TIQ) backbone were synthesized. Their application in the catalytic asymmetric Henry reaction was investigated with comparison to a corresponding TIQ oxazoline ligand. The Cu(II)-oxazoline complex was more reactive and furnished moderate enantioselectivities up to 61:36 (syn:anti) with 75:25 diastereomeric excess, while the Cu(II)-thiazole complexes had lower selectivity. This is the first example where a direct comparison between an N, N-type thiazole and oxazoline ligands has been studied. KEYWORDS Tetrahydroisoquinoline, thiazole, oxazoline, Henry reaction, enantioselectivity.
S. Afr. J. Chem. 01/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: A series of novel TIQ based N,N'-oxide ligands were synthesized and screened for their catalytic activity in the enantioselective conjugate addn. of thioglycolate to chalcones. Bulky groups on the side chain of the TIQ backbone provided the highest enantioselectivity of up to 88% with 10 mol % catalyst loading. It was also obsd. that these reactions proceeded optimally in the presence of dichloromethane as a solvent. Screening of various metals emphasized La(OTf)3 as the ideal pre-catalyst for this particular reaction. [on SciFinder(R)]
Tetrahedron Asymmetry 01/2012; 23(8):616-622. · 2.65 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The title compound, C(18)H(21)NO(3)·2.33H(2)O, is the fourth reported member in a series of (1R,3S)-6,7-dimeth-oxy-1-phenyl-1,2,3,4-tetra-hydro-isoquinoline derivatives used in catalysis as ligands (or their precursors). The N-heterocycle in the structure adopts a half-chair conformation. The dihedral angle between the benzene rings is 77.29 (13)°. There are three ill-resolved water molecules of crystallization in the structure (one of them rotationally disordered about a threefold axis) involved in short contacts probably due to hydrogen bonding.
Acta Crystallographica Section E Structure Reports Online 01/2011; 67(Pt 3):o700. · 0.35 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The structure of the title compound, C13H14O2, a pentacycloundecane cage derivative, exhibits unusual Csp3—Csp3 single-bond lengths ranging from 1.505 (3) to 1.607 (2) Å and strained bond angles as small as 88.7 (1)° and as large as 121.0 (2)°. In this meso compound, an internal non-crystallographic mirror plane exists, bisecting the molecule. In the crystal, weak C—H...O hydrogen bonds link the molecules into an infinite spiral about a twofold screw axis along the [100] direction.
Acta Crystallographica Section E. 01/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: The structure of the title compound, C(13)H(14)O(2), a penta-cyclo-undecane cage derivative, exhibits unusual Csp(3)-Csp(3) single-bond lengths ranging from 1.505 (3) to 1.607 (2) Å and strained bond angles as small as 88.7 (1)° and as large as 121.0 (2)°. In this meso compound, an inter-nal non-crystallographic mirror plane exists, bis-ecting the mol-ecule. In the crystal, weak C-H⋯O hydrogen bonds link the mol-ecules into an infinite spiral about a twofold screw axis along the [100] direction.
Acta Crystallographica Section E Structure Reports Online 01/2010; 66(Pt 8):o1901-2. · 0.35 Impact Factor
-
Annalen der Chemie und Pharmacie 12/2009; 2010(5):972 - 980. · 3.10 Impact Factor
