56439-07-7Relevant academic research and scientific papers
Regulation of the flexibility of planar chiral [2.2]paracyclophane ligands and its significant impact on enantioselectivity in asymmetric reactions of diethylzinc with carbonyl compounds
Wu, Xun-Wei,Zhang, Tang-Zhi,Yuan, Ke,Hou, Xue-Long
, p. 2357 - 2365 (2004)
A series of planar chiral ligands derived from [2.2]paracyclophane were synthesized and applied as catalysts in enantioselective additions of diethylzinc to aldehydes and α,β-unsaturated ketones. When ligand 10 with a dimethyl hydroxymethyl as the substituent was used, the enantioselectivity of the reaction of diethylzinc with aldehydes was much higher than when using ligand 3c with diphenyl hydroxymethyl as the substituent. The situation was the same with the 1,4-addition of diethylzinc to α,β-unsaturated ketones with 63-83% ee being obtained when the hydroxymethyl substituted ligand 7b was used, while almost no enantioselectivity was afforded if ligand 3c was used. The role of planar chirality is also studied.
Oxazoline mediated routes to a unique amino-acid, 4-amino-13-carboxy[2.2]paracyclophane, of planar chirality
Marchand, Anne,Maxwell, Anderson,Mootoo, Baldwin,Pelter, Andrew,Reid, Alicia
, p. 7331 - 7338 (2007/10/03)
Efficient syntheses leading to 4-amino-13-carboxy[2.2]paracyclophane and derivatives are described. Novel oxazolinyl[2.2]paracyclophanes are used as intermediates and the oxazolinyl and amide groups are shown to be strong ψ-geminal directing groups. Compounds with potential as catalysts have been made. (C) 2000 Elsevier Science Ltd.
Transmission of Polar Effects. Part 15. Ionisation and Esterification with Diazodiphenylmethane of Paracyclophane-4-carboxylic Acid and its Pseudo-bromo-substituted Derivatives, and the Alkaline Hydrolysis of their Methyl Esters
Socrates, Acevedo,Bowden, Keith
, p. 2045 - 2048 (2007/10/02)
The pKa values of paracyclophane-4-carboxylic acid and its four pseudo-bromo-substituted derivatives have been determined in 80percent (w/w) 2-methoxyethanol-water at 25 deg C.The rate coefficient for the esterification of these acids with diazodiphenylmethane have been measured in 2-methoxyethanol at 30 deg C.The rate coeeficients for the alkaline hydrolysis of the corresponding methyl esters have been determined in 70percent (v/v) dimethyl sulphoxide-water at both 56.3 and 76.3 deg C.In the ionisation and esterification reactions both normal and reversed substituent polar effects were detected.Kirkwood-Westheimer calculations were carried out for the ionisation reaction and account for ΔpKa values both qualitatively and (for the pseudo-ortho, -meta-, and -para-isomers) quantitatively.In the alkaline hydrolysis of the esters, significant steric retardation was observed for the pseudo-gem-isomer.
