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[1] [2] [3] An example is the synthesis of dibenzylideneacetone ((1E, 4E)-1,5-diphenylpenta-1,4-dien-3-one). [ 4 ] Quantitative yields in Claisen–Schmidt reactions have been reported in the absence of solvent using sodium hydroxide as the base and plus benzaldehydes . [ 5 ]
The pinacol reaction is extremely well-studied and tolerates many different reductants, including electrochemical syntheses.Variants are known for homo- and cross-coupling, intra- and inter-molecular reactions with appropriate diastereo- or enantioselectivity; [2] as of 2006, the only unsettled frontier was enantioselective cross-coupling of aliphatic aldehydes. [3]
The Baeyer–Drewsen indigo synthesis (1882) is an organic reaction in which indigo is prepared from 2-nitrobenzaldehyde and acetone [1] [2] The reaction was developed by von Baeyer and Viggo Drewsen in 1880 to produce the first synthetic indigo at laboratory scale. This procedure is not used at industrial scale.
Benzylideneacetone can be efficiently prepared by the base-induced condensation of acetone and benzaldehyde: [3]. CH 3 C(O)CH 3 + C 6 H 5 CHO → C 6 H 5 CH=CHC(O)CH 3 + H 2 O. However, the benzylideneacetone formed via this reaction can undergo another Claisen-Schmidt condensation with another molecule of benzaldehyde to form dibenzylideneacetone.
An example is shown below. [9] Scheme 2. An intramolecular benzoin addition. Since the products of the reaction are thermodynamically controlled, the retro benzoin addition can be synthetically useful. If a benzoin or acyloin can be synthesized by another method, then they can be converted into the component ketones using cyanide or thiazolium ...
This can be economically viable if the products can be separated and both have a value; the commercial conversion of furfural into furfuryl alcohol and 2-furoic acid is an example of this. [6] Alternatively, higher yields of one product (usually the alcohol) can be achieved in the crossed Cannizzaro reaction , in which a sacrificial aldehyde is ...
Chalcone is usually prepared by an aldol condensation between benzaldehyde and acetophenone. [ 6 ] This reaction, which can be carried out without any solvent, is so reliable that it is often given as an example of green chemistry in undergraduate education.
An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to give a conjugated enone.