213987-19-0Relevant academic research and scientific papers
Asymmetric addition of dimethylzinc to alkylidenmalonates mediated by phosphorous ligands: A new synthetic route to floral fragrances
Superchi, Stefano,Marchitiello, Valeria,Pisani, Laura,Scafato, Patrizia
body text, p. 761 - 767 (2012/01/13)
Six new phosphite ligands were prepared and their efficiency as chiral ligands was investigated in the copper-catalyzed asymmetric conjugate addition of dimethylzinc to diethyl 3-phenylpropylidenmalonate (5), affording the addition product with ees up to 74%. Moreover, a simple and straightforward route to floral fragrances Phenoxanol, Citralis, and Nitrile Citralis in optically active form through the above cited reaction was proposed. Chirality, 2011. 2011 Wiley-Liss, Inc. Copyright
Catalytic enantioselective allyl- and crotylboration of aldehydes using chiral diol·SnCl4 complexes. Optimization, substrate scope and mechanistic investigations
Rauniyar, Vivek,Zhai, Huimin,Hall, Dennis G.
supporting information; experimental part, p. 8481 - 8490 (2009/02/02)
We report a novel class of C2-symmetric chiral diols derived from the hydrobenzoin skeleton. The combination of these diols with SnCl 4 under Yamamoto's concept of Lewis acid assisted Bronsted acidity (LBA catalysis) leads to high levels of asymmetric induction in the allylboration of aldehydes by commercially available allylboronic acid pinacol ester 1a. The corresponding homoallylic alcohol products of synthetically useful aliphatic aldehydes are obtained in excellent yields with up to 98:2 er. This combined acid manifold is also efficient in catalyzing the diastereo- and enantioselective crotylboration of aldehydes, thus providing the propionate units in >95:5 dr and up to 98:2 er. The X-ray crystal structure of the optimal diol·SnCl4 complex, Vivol (4m)·SnCl 4, unambiguously shows the Bronsted acidic character of this LBA catalyst and its highly dissymmetrical environment. Further controls have ruled out a possible boron transesterification mechanism with the chiral diol and point to LBA catalyst-derived activation of the pinacol allylic boronates 1. Due to slow dissociation of the diol·SnCl4 complex, a small excess of diol is required in order to suppress a competing racemic cycle catalyzed by free SnCl4.
Catalytic enantioselective and catalyst-controlled diastereofacial- selective additions of allyl- and crotylboronates to aldehydes using chiral Bronsted acids
Rauniyar, Vivek,Hall, Dennis G.
, p. 2426 - 2428 (2007/10/03)
(Chemical Equation Presented) Towards the ideal: A chiral diol-SnCl 4 complex is applied to the allylboration of aldehydes (see scheme). This approach highlights the use of chiral Bronsted acid catalysis in the development of an ideal method for the allylation of aldehydes which would display high diastereo- and enantioselectivity, wide substrate scope, and high practicality (ease of use, low cost, and low environmental impact).
Titanium(IV) iodide promoted pinacol coupling
Hayakawa, Ryuuichirou,Shimizu, Makoto
, p. 724 - 725 (2007/10/03)
Pinacol coupling of aromatic aldehydes was efficiently promoted by titanium tetraiodide in propionitrile to give the 1,2-diol derivatives with high dl-selectivities in high yields.
Monobenzylether of (R,R)-1,2-diphenylethane-1,2-diol as chiral auxiliary in the diastereoselective reduction of α-ketoesters
Superchi, Stefano,Contursi, Michela,Rosini, Carlo
, p. 11247 - 11254 (2007/10/03)
The α-ketoester 4a, prepared in 3 steps from (R,R)-1,2-diphenylethane- 1,2-diol can be reduced with several agents providing the corresponding α- hydroxyester 5 with diastereoselectivities up to 56%. This selectivity has been interpreted as due to carbony
