Enantio- and diastereoselective synthesis of highly substituted benzazepines by a multicomponent strategy coupled with organocatalytic and enzymatic procedures
Enantiomerically pure 4,5-dihydro-1H-benzo[c]azepines with three contiguous stereogenic centers have been assembled by convergent strategy with a good control of diastereoselectivity. The two steps are as follows: an asymmetric organocatalytic Mannich reaction performed on Boc-imines of o-(azidomethyl) benzaldehydes, followed by a one-pot Staudinger/aza-Wittig/Ugi-Joullie sequence. The latter reaction represents one of the first examples of diastereoselective Ugi three-component reaction on a seven-membered cyclic imine. The o-azidomethylbenzaldehydes have been synthesized employing a simple and efficient chemoenzymatic strategy from commercially available building blocks.
Click-connected ligand scaffolds: macrocyclic chelates for asymmetric hydrogenation
Click chemistry is used to construct ligand scaffolds for a series of chiral diphosphites. Enantioselectivity as high as 97% ee is obtained using these click ligands in rhodium-catalyzed asymmetric hydrogenation. Control experiments and spectroscopic data suggest that a 16-membered P,P-macrocyclic Rh(1) chelate is formed.
Qing, Zhang,Takacs, James M.
p. 545 - 548
(2008/09/17)
A simple one-pot procedure for the direct conversion of alcohols to azides via phosphate activation
(Equation presented) A one-pot procedure was developed to prepare efficiently alkyl azides from alkanus using bis(2,4-dichlorophenyl) phosphate activation. 4-(Dimethylamino)pyridine was used as a base, and phosphorylpyridinium azide is believed to be the activating agent under this condition.
Yu, Chengzhi,Liu, Bin,Hu, Longqin
p. 1959 - 1961
(2007/10/03)
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