Catalytic asymmetric hydroboration with oxazaborolidines

The cyclic secondary boranes derived from ephedrine and pseudoephedrine undergo rhodium complex-catalysed hydroboration of styrenes; both the regiochemistry and derived enantiomeric excess depend strongly on the structure of the catalyst with the ferrocenebiphosphine complex (12d) the most promising to date.     

Catalytic asymmetric fluorinations

The appearance of structurally diverse fluorinating reagents displaying a large spectrum of reactivity has been critical to the development of the catalytic asymmetric fluorination processes known to date. In this article, we discuss how this area of research emerged and which strategies have allowed for the successful development of both nucleophilic and electrophilic catalytic enantioselective fluorinations. We also present the fundamental understanding of catalytic activity and enantioselectivity for the most efficient processes and highlight the first synthetic application with the preparation of a complex fluorinated target.     

Catalytic asymmetric Michael addition with curcumin derivative

Catalytic asymmetric Michael additions with curcumin derivatives were achieved by a new series of tertiary amine-thiourea organocatalysts to afford the Michael adducts in high yields and excellent enantioselectivities.     

Catalytic asymmetric epoxidation of alkenes with arabinose-derived uloses

Four l-erythro-2-uloses were readily prepared from l-arabinose via a reaction sequence involving Fischer glycosidation, acetalization and oxidation. Bulky steric sensors at the anomeric center could enhance the stereoselectivity of the dioxirane epoxidation and one of the uloses performed with good enantioselectivity towards trans-stilbene (up to 90% ee). However, the catalysts decomposed during the epoxidation and the maximum chemical yield was only 13% under the basic conditions. Three l-threo-3-uloses could overcome the decomposition problem based on the electron withdrawing effect of the ester group(s) α to the ketone functionality. The best chemical yield was up to 93% using a ketone with two flanking ester groups. One of the improved uloses displayed moderate enantioselectivity towards trans-disubstituted and trisubstituted alkenes (40-68% ee).     

Catalytic asymmetric diastereodivergent deracemization

Your wish is my command: Deracemization is a powerful strategy wherein a racemate is converted into a 100?% yield of a single enantiopure product. A new concept in catalytic deracemization is presented, in which a racemate with n?stereogenic elements can be selectively converted into each one of 2(m) (m = number of chiral centers of the product) different enantiopure products, by simple tuning of the reaction conditions.     

Catalytic asymmetric Pictet-Spengler reaction

A catalytic asymmetric Pictet-Spengler reaction has been developed, wherein treating substituted tryptamines with an aldehyde in the presence of a catalytic amount of a chiral phosphoric acid provides the corresponding tetrahydro-beta-carboline derivatives in high yields and enantiomeric excesses. The reaction works well with both aliphatic and aromatic aldehydes.     

Catalytic asymmetric olefin metathesis

This paper provides a survey of the first examples of efficient catalytic enantioselective olefin metathesis reactions. Mo-catalyzed asymmetric ring-closing (ARCM) and ring-opening (AROM) reactions allow access to myriad optically enriched compounds that are otherwise difficult to access.     

Catalytic asymmetric Henry reaction

The classical Henry reaction, the coupling of a nitroalkane with a carbonyl compound in the presence of a base, is an important C–C bond forming reaction in organic chemistry giving β-nitroalcohols, which are useful synthons in organic synthesis. However, an asymmetric version of the reaction, that has been developed recently, gives a new dimension to the classical Henry reaction whereby the control of stereochemistry of two newly generated carbon centres has become possible. In this review, the various catalytic methods for this purpose are discussed.     

催化不对称Friedel-Crafts反应

傅-克反应是有机化学中最基本的反应之一,但是对于催化的不对称傅-克反应的研究则处于起步阶段。最近这方面的研究获得了突破,本文简要介绍了催化不对称傅-克反应的最新动态,包括各种手性Lewis酸催化体系的开发及其在不对称合成中的应用。     

Catalytic asymmetric formation of beta-sultams

beta-Sultams, highly strained sulfonyl analogues of beta-lactams, were prepared enantio- and diastereoselectively by tertiary amine catalyzed [2 + 2] cycloaddition reactions. The title compounds are practical precursors of highly enantioenriched biologically interesting beta-aminosulfonyl derivatives.     

Catalytic asymmetric hydrogenation of aldehydes

Racemic alpha-arylaldehydes provide the corresponding primary alcohols via dynamic kinetic resolution in excellent enantioselectivities and yields upon hydrogenation using a Noyori ruthenium catalyst; for example, the biologically active (S)-enantiomer of the non-steroidal anti-inflammatory drug ibuprofen could be synthesized via catalytic enantioselective hydrogenation of aldehyde followed by oxidation with potassium permanganate in 76% isolated yield and 96 : 4 er.     

Condensation of 2,3,3-trimethylindolenine with salicylaldehydes

2,3,3-Trimethylindolenine undergoes condensation with aromatic aldehydes to give the corresponding 2-styrylindolenines. It is shown by means of spectroscopic data that hydroxystyrylindolenines rather than the corresponding merocyanines or spiropyrans are formed in the reaction with salicylaldehydes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1221–1223, September, 1978.     

Catalytic asymmetric heterodimerization of ketenes

In this Communication we describe an unprecedented catalytic asymmetric heterodimerization of ketenes of wide substrate scope. The alkaloid-catalyzed method provides access to ketene heterodimer β-lactones and allows even two different monosubstituted ketenes to be cross-dimerized, with excellent enantioselectivity (17 examples with ≥90% ee) and excellent heterodimer regioselectivity observed in all cases.