160031-05-0Relevant articles and documents
Boranes in synthesis - VII. Synthesis of 2-dialkylamino-6,6- dimethylbicyclo[3.1.1]heptan-3-ols from (R)-(+)-nopinone. Chiral auxiliaries for the addition of diethylzinc to aromatic aldehydes
Goralski, Christian T.,Chrisman, William,Hasha, Dennis L.,Nicholson, Lawrence W.,Rudolf, Philip R.,Zakett, Donald,Singaram, Bakthan
, p. 3863 - 3871 (1997)
The reaction of (1R,5S)-(+)-nopinone with secondary amines in cyclohexane with the azeoptropic removal of water afforded excellent yields of the corresponding enamines. Hydroboration of these enamines with BMS followed by methanolysis and oxidation with basic hydrogen peroxide gave the corresponding (1R,2S,3S,5R)-2-dialkylamino-6,6-dimethylbicyclo[3.1.1]heptan- 3-ols. These amino alcohols, in spite of their trans geometry, served as chiral auxiliaries for the addition of diethylzinc to aromatic aldehydes to give nearly quantitative yields of the corresponding (R)-1-aryl-1-propanols with 52 to 80% ee.
Dual stereoselectivity in the dialkylzinc reaction using (-)-β-pinene derived amino alcohol chiral auxiliaries
Binder, Caitlin M.,Bautista, April,Zaidlewicz, Marek,Krzeminski, Marek P.,Oliver, Allen,Singaram, Bakthan
supporting information; experimental part, p. 2337 - 2343 (2009/08/07)
(+)-Nopinone, prepared from naturally occurring (-)-β-pinene, was converted to the two regioisomeric amino alcohols 3-MAP and 2-MAP in very good yield and excellent isomeric purity. Amino alcohol 3-MAP was synthesized by converting (+)-nopinone to the corresponding α-ketooxime. This was reduced to the primary amino alcohol and was converted to the morpholino group through a simple substitution reaction. 3-MAP was characterized by X-ray crystallography, which displayed the rigidity of the pinane framework. Amino alcohol 2-MAP was prepared from its trans isomer 2, which in tum was synthesized via hydroboration/ oxidation of the morpholine enamine of (+)-nopinone. Two-dimensional NMR was used to characterize amino alcohol 2-MAP, and NOE was used to confirm its relative stereochemistry. These amino alcohols were employed as chiral auxiliaries in the addition of diethylzinc to benzaldehyde to obtain near-quantitative asymmetric induction in the products. The use of 3-MAP yielded (S)-phenylpropanol in 99% ee, and its regioisomer 2-MAP gave the opposite enantiomer, (R)-phenylpropanol, also in 99% ee. Other aromatic, aliphatic, and α,β-unsaturated aldehydes were implemented in this method, affording secondary alcohols in high yield and enantiomeric excess. Amino alcohols 2-MAP and 3-MAP were also found to be useful in the dimethylzinc addition reaction, both catalyzing the addition to benzaldehyde with nearly quantitative ee. Regioisomeric amino alcohols 2-MAP and 3-MAP, even though they were prepared from one enantiomer of nopinone, provide antipodal enantiofacial selectivity in the dialkylzinc addition reaction. This circumvents the necessity to synthesize amino alcohols derived from (-)-nopinone, which in tum requires the unnatural (+)-β-pinene. Possible mechanistic insights are offered to explain the dual stereoselectivity observed in the diethylzinc addition reaction involving regioisomeric, pseudo-enantiomeric amino alcohols 3-MAP and 2-MAP.
Enantiomerically pure zirconium and hafnium complexes containing a chiral cyclopentadiene derivative prepared from (-)-β-pinene
Rousset, Christophe J.,Iyer, Suresh,Negishi, Ei-Ichi
, p. 3921 - 3926 (2007/10/03)
Chirally homogeneous (1S,8R)-3,5,9,9-tetramethyltricyclo[6.1.1.02,6] deca-2,5-diene 1 has been prepared in five steps and 42% overall yield from (-)-β-pinene; its successive treatment first with n-BuLi and then with ZrCl4 or HfCl4 provides, in high yields with high π-facial selectivity, the corresponding dichlorobis{η5-(1S,8R)-3,5,9,9-tetramethyltricyclo [6.1.1.02,6]deca-3,5-dien-2-yl}zirconium or hafnium, respectively.
