209251-28-5Relevant articles and documents
Enantioselective total synthesis of the proposed structure of macrolide iriomoteolide-1b
Ye, Zhengqing,Gao, Tingyi,Zhao, Gang
experimental part, p. 5979 - 5989 (2011/09/19)
An enantioselective total synthesis of the proposed structure of macrolide iriomoteolide-1b has been achieved by a convergent protocol, which was featured by an enantioselective organocatalytic transfer hydrogenation of enal, a Julia-Kocienski olefination
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; scheme or table, 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.
Scope and limitations of the scandium-catalyzed enantioselective addition of chiral allylboronates to aldehydes
Gravel, Michel,Lachance, Hugo,Lu, Xiaosong,Hall, Dennis G.
, p. 1290 - 1302 (2007/10/03)
Scandium triflate catalyzes the addition of camphor-derived allyl-, methallyl-, and crotylboronates to aldehydes to provide homoallylic alcohols with excellent diastereo- and enantioselectivity. Aromatic, aliphatic, and propargylic aldehydes can be used successfully in this system. Additional advantages of the camphor-diol allylboronates are their ease of synthesis, their availability in both enantiomeric forms, and their stability towards silica gel chromatography. The usefulness of this methodology is further demonstrated by the gram-scale synthesis of various homoallylic alcohols of high enantiomeric excess and by the concise synthesis of the pheromone (4S)-2-methyloctan-4-ol. 1 Introduction 2 Results and Discussion 2.1 Optimization 2.2 Substrate Scope 2.3 Synthetic Applications 2.4 Mechanistic Considerations 3 Conclusion.
