Benzaldehydes, reactions

Searching for other oscillatory autoxidation reactions led Druliner and Wasserman to use cyclohexanone as a substrate instead of benzalde-hyde (168). Unlike the simple stoichiometry found for the benzaldehyde reaction, the ketone gives at least six or more products, and the relative amounts of these vary substantially with the experimental conditions (Scheme 7). 

Scheme 28. Proposed structure of intermediates in 135b Cu catalyzed aldol reaction of dienolsilane 411 and benzaldehyde (reaction monitored by in situ IR spectroscopy). [Adapted from (255).]...

Provided that the influence of the water-ethanol composition on the reaction involving addition of hydroxide ions to benzaldehydes can be characterized by any parameter Yj (the application of Y- used for benzoic acid dissociations in ethanol-water mixtures (28) might be doubtful), application of the relation pYt - pyo = C(Yi - Y0) would indicate that the value of C (0.638) for benzoic acids (28) and —0.573 for anilines (29) is close to zero for the benzaldehyde reaction (4). 

L-Prolinethioamides (39, R = alkyl including chiral alkyl), prepared from proline and amines, are effective in acetone-benzaldehyde reactions.110 Mechanistic studies focused in particular on suppression of non-enantioselective side-reactions, and also on the role of the side-chain of the catalyst acting as hydrogen bond donor, especially as the thioamides (with their more acidic N—H protons) are more catalytic than their amide analogues. 

IV -Benzyl-Af -prolylhydrazide (42), in its protonated form, gives high ee in the acetone-benzaldehyde reaction.114... 

Chloro-2-methylquinalin was converted into 3-(2-(7-chloro)-2-quinolinyl)ethenyl)benzaldehyde. Reaction was carried out according to a method described in U.S. Pat. No. 4,851,409... 

Houk next examined the aldol reaction of cyclohexanone with benzaldehyde (Reaction 6.20) and isobutyraldehyde (Reaction 6.21) with (6)-proline as the catalyst. Four diastereomeric TSs starting from the enamine formed from cyclohexanone and proline were optimized at B3LYP/6-31G for each reaction. These transitions states, 53 and 55, are shown in Fignre 6.23. In all of these TSs, proton transfer from the carboxylic acid group to the carbonyl oxygen accompanies the formation of the new C-C bond, creating a carboxylale and alcohol product. 

Since the measured yields of the phenolic products corresponded to 30% OH yield, the ipso adduct formation is limited to 10% OH yield. Since the combined G value of m- and -hydroxybenzaldehydes in NjO-saturated solutions in the presence of IrCl is 1.7, only 30% OH seems to add to the ring. The reason for low phenolic yields in the case of benzaldehyde is the possibility of another reaction channel leading to the formation of the exocyclic OH adduct (structure 5) from the addition of OH to the carbonyl group of benzaldehyde [reaction (4)]. 

The addition of the phthalimido anion to triesters of 2-phosphonopropenoic acid at room temperature gives an initial adduct, which is unexpectedly inert to benzaldehyde reaction but which adds to a second molecule of the phosphonic diester to form a second carbanion the latter undergoes an intramolecular WEH condensation to give the heterocyclic system 371 indolizine and quinolizine phosphonic diesters have been similarly obtained from maleimide, succinimide and glutarimide anions ". The ability of piperidine to add to the compounds 372 decreases in the order R R = (BuO)H (exothermic reaction) > (BuO)2 > (BuO)Me > Bu2 (the last requires heat) ". Ethenylphosphonic diamides (372 R = r2 = NR2) are unreactive to nucleophiles (by virtue of reduced electrophilic character at phosphorus and thus reduced electron attraction from the carbon-carbon double bond) but are reactive to electrophilic reagents. ... 

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