Get Asymmetric Organocatalysis PDF

By Benjamin List

ISBN-10: 3642028152

ISBN-13: 9783642028151

As nucleophiles, basic alkenes tend to be so unreactive that purely hugely lively electrophiles, resembling carbocations, peroxides, and halogens will react with them. For the new release of carbon-carbon bonds, milder tools will frequently be required. thankfully, it really is attainable to extend the reactivity of alkene-type p-nucleophiles through introducing electron-donating substituents. Substitution of 1 H with an OH or OR offers an enol or a vinyl ether, that are already far better nucleophiles. utilizing nitrogen rather than oxygen, one obtains even larger nucleophiles, enamines. Enamines are one of the so much reactive impartial carbon nucleophiles, displaying charges which are even equivalent to a few charged nucleophiles, reminiscent of enolates [1, 2]. such a lot enamines, regrettably, are delicate to hydrolysis. The mum or dad enamine, N, N-dimethylvinylamine, has in truth been ready [3], yet seems to be uns- ble. Enamines of cyclic ketones and lots of aldehydes can simply be remoted, notwithstanding [4-7]. The instability of enamines may well initially seem to curb the software of enamines as nucleophiles, yet truly this estate will be considered as an additional advantage: enamines may be with no trouble and swiftly generated catalytically through the use of an appropriate amine and a carbonyl compound. The condensation of aldehydes or ketones with amines at the beginning gives an imine or iminium ion, which then swiftly loses a proton to have enough money the corresponding enamine (Scheme 1).

Show description

Read or Download Asymmetric Organocatalysis PDF

Similar inorganic books

Download e-book for kindle: The Structure and Properties of Water by D. Eisenberg, W. Kauzmann

The authors have correlated many experimental observations and theoretical discussions from the clinical literature on water. issues coated contain the water molecule and forces among water molecules; the thermodynamic houses of steam; the constructions of the ices; the thermodynamic, electric, spectroscopic, and shipping homes of the ices and of liquid water; hydrogen bonding in ice and water; and types for liquid water.

Get The Porphyrin Handbook. Applications of Phthalocyanines PDF

The Porphyrin guide, quantity 19: functions of Phthalocyanines presents info pertinent to each point of the chemistry, synthesis, spectroscopy, and constitution of phthalocyanines. This ebook examines the biology and scientific implications of porphyrin platforms. geared up into 5 chapters, this quantity starts with an outline of the fundamental photobiology of phthalocyanines, their structure–activity relationships, mechanisms of motion in numerous organic platforms, and their strength functions for numerous scientific reasons.

Download PDF by P. Powell: The Chemistry of the Non-Metals

This e-book is a brand new try and interrelate the chemistry of the non-metals. within the early chapters, easy compounds of the non-metals with the halogens, hydrogen, and oxygen are surveyed, allowing a wide region of chemistry to be mentioned with out the load of too many proof. The structural relationships within the elemental kinds of the non-metals are then used as an advent to the catenated compounds, together with the boron hydrides.

Extra info for Asymmetric Organocatalysis

Example text

L. Moore, T. Rovis The observed diastereoselectivity of the protonation event may be explained by Model C (Scheme 13). In Model C, an intermolecular proton transfer would yield the minor diastereomer. Alternatively, the proton transfer may be intramolecular and occur from the more sterically hindered face of the enolate, providing D. Bn H R EtO N O O N N Ph Bn EtO O H R H O O H O c N N Ph N d Scheme 13 Intramolecular protonation The mechanistic hypothesis was tested with experiments involving a pair of substrates differing only in olefin geometry about the a,b-unsaturated ester.

The reaction scope is quite general and tolerates both aromatic and aliphatic aldehydes (Table 9). Carbene Catalysts 97 O H O 20 mol% catalyst Me CO2Et Me PhMe, 23 oC, 24h CO2Et O H O 93 94 N Bn BF4 N N Ph Bn 76a 85-88% 90% ee 3:1 to 15:1 dr (8) N N Ph N 95 88% 90% ee 15:1 dr Table 9 Highly diastereoselective intramolecular Stetter reaction O H R O Bn EWG a O H CO2Et 95 O 20 mol% 98 Yield ee (%) (%) dr Entry 97 Product N N 92 O 97 Yield ee (%) (%) dr d O Et b O H CO2Et 80 84 20:1 5 e 95 c O 95 18:1 O O H H CO2Et O 94 99 50:1 80 88 15:1 H O O 80 O Bn 3 O H H O 2 EWG R Entry 97 Product 35:1 4 H CF3 PhMe, 23 oC, 24h 96 1 N 83 13:1 6 f O O H H N Ph O 98 J.

L. Moore, T. Rovis Nicolaou and co-workers recently published a formal synthesis of (±)-platensimycin utilizing Stetter methodology [102]. Aldehyde 162 was treated with achiral N-pentafluorophenyl pre-catalyst 164 and readily underwent cyclization to yield 163 as a single diastereomer (Scheme 26). After an additional seven steps late stage intermediate 165 was formed to complete the formal synthesis. O F N N N F BF4 F F 100 mol% 164 H Br O O F O Br Et3N, CH2Cl2, 45 C 162 163 64% OH O O O 7 steps O H OH OH Me 165 Me O N H O (±)-platensimycin Me Scheme 26 Nicolaou et al.

Download PDF sample

Asymmetric Organocatalysis by Benjamin List


by Michael
4.0

Rated 4.43 of 5 – based on 3 votes