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Application of Tishchenko reaction to the direct synthesis of esters from aldehydes bears the shortcomings in being wasteful on part of aldehydes and compulsory predestination of the alkoxy moieties. More controllable routes are those via carboxylic acids and acetals. Several reagents have proven effective for oxidation of the latter, e.g., N-bromosuccinimide,1 peracids2, and ozone.3

The polymerizations of 2,3-epoxypropanal (glycidaldehyde) (1a) and its 2-methyl and 2,3-dimethyl derivatives (1b, 1c) were studied in the temperature range of 20–50°C in the presence of aluminum 2-propoxide as catalyst. The polymerization of these epoxyaldehydes was found to proceed in two stages. A Tishchenko reaction leading to the formation of the corresponding esters 2 was found to be predominant in the first stage of polymerization. In the case of aldehydes having a methyl group in the 2-position, the β-lactones 3 are formed. Polymer chain growth takes place in the second stage of the polymerization reaction with the participation of the epoxide groups of the dimers 2 produced in the first stage, which leads to the formation of non-crosslinked polyethers having short ester side chains with epoxide groups or side chains with β-lactone rings. The structure of the starting monomer was shown to determine directly the differences in polymerization rates and in the structure of the polymers and intermediate products. Es wurde die Polymerisation von 2,3-Epoxypropanal (Glyzidaldehyd) (1a) sowie dessen 2-Methyl- und 2,3-Dimethyl-Derivate (1b und 1c) in Anwesenheit von Aluminium-2-propylat bei Temperaturen von 20 bis 50°C untersucht. Dabei wurde festgestellt. das die Polymerisation dieser Epoxyaldehyde zweistufig verlauft. In der ersten Stufe fuhrt die Tischtschenko-Reaktion als Hauptreaktion zur Bildung der entsprechenden Ester 2. Im Fall der Epoxyaldehyde, die in der 2-Stellung eine Methylgruppe besitzen, entstehen die β-Lactone 3. Das Wachstum der Polymerkette findet in der zweiten Stufe der Reaktion unter Beteiligung der Epoxidgruppen des in der ersten Reaktionsstufe gebildeten Dimeren 2 statt. Dahei entstehen lineare Polyather mit kurzen Esterseitenketten, die eine Epoxidgruppe enthalten, oder kurze Seitenketten mit einem β-Lactonring. Es wurden Unterschiede der Polymerisationsgeschwindigkeit sowie Unterschiede der Struktur der Polymeren und Zwischenprodukte in Abhangigkeit von der Struktur der Ausgangsmonomeren festgestellt.

The effect of carboxylic acids and anhydrides on the Tishchenko reaction of benzaldehyde with aluminum benzyloxide have been studied kinetically by means of GLC. Acetic and benzoic acids and their anhydrides promote the reaction, but sulfonic acids, benzyl alcohol, water, sodium carboxylates do not. The rates vary with molar ratio of promoters vs aluminum benzyloxide and the corrected molar ratio of these promoters vs aluminum benzyloxide at maximum rate is ca. unity. Aluminum alkoxide undergoes dealkoxycarboxylation to give benzyl alcohol or benzyl carboxylates by carboxylic acids or anhydrides, respectively. Dialkoxyaluminum carboxylate is probably an active catalyst for the hydride transfer step.

Reactions between diethylaluminum s-butoxide and n-butyraldehyde have been carried out at several temperatures from −65 to 40°C. The reaction mixtures were then treated with glacial acetic acid and subjected to vapor-phase chromatographic analysis (vpc). The products analyzed by vpc were methyl ethyl ketone, butanol-1, s-butyl n-butyrate, n-butyl n-butyrate, 2-ethyl-2-hexenal, and 2-ethyl-1, 3-hexanediol 1-n-butyrate. The last two compounds were formed only at reaction temperatures above 20°C, and methyl ethyl ketone was not formed below −40°C. The reaction of the ethylaluminum group with the aldehyde group was not observed. Finally, the interrelationship of the three reactions involving aluminum alkoxide and aldehyde, the Meerwein-Ponndorf-Verley reduction, the Tishchenko reaction, and the aldehyde polymerization, has been discussed.

The esterification of b6nzaldehyde has been studiedi over solid NaOH, NaOH-SiO2, A120s, SrO2, BaOz, SrO and CaO. The catalytic'activity was found not. only to closely relate with the basic properties, but also to relate, with the acidic proPerties (Fig., 6). lt was o. bserv. ed that two d-hYdrogens of benzyl groups of benzyl benzoate (major product) and benzyl alcohol (miner product) produced by the esterification of ibenzaldehyde-a-at were deuterat. ed. and t-hqt there The catalytic activity was was no hydrogen isotope effect(kH/kD=1, o, 2)(Figs, 1and 2), decreased by the addition of benzoic acid or phenol, but not by. the addition of benzene or cyclohexane' (Figs.3, 4 and 5). Thg amount of benzylE alcohol formed was increased by the addition of aliphatic alcohols (Fig.4).On the basi's of the observed results, it has been concluded that the aetive sites for the esterification are metal bezylates and those for the formation of metal benzylate consist of both basic sites (surface OZ) and Lewis acid sites (Ca2" etc. ). The mechanism of the esterification has been N@discussed in detail and 'c'ompared, with those of Cannizzaro and Tishchenko reaction in homogeneous system

Reactions of n-butyraldehyde caused by tris(trimethylsiloxy)aluminum were examined and compared with those caused by aluminum t-butoxide. In the Tishchenko reaction of aldehyde caused by aluminum t-butoxide, the t-butoxy group was first transferred from aluminum to the carbonyl group of n-butyraldehyde to produce t-butyl n-butyrate. On the other hand, we observed no formation of trimethylsilyl n-butyrate by the transfer of the trimethylsiloxy group to n-butyraldehyde. However, esters of the n-butyric acid of n-butanol and the glycol derived from the aldol of n-butyraldehyde were found in the system with tris(trimethylsiloxy)aluminum: their formation was ascribed to the aluminum alkoxide species which was first formed between tris(trimethylsiloxy)aluminum and the aldol of n-butyraldehyde. The above assumption has been supported by the finding that aluminum t-butoxide caused the Tishchenko reaction of benzaldehyde, producing benzyl benzoate almost quantitatively, whereas tris(trimethylsiloxy)aluminum did no...

Tishchenko reaction of benzaldehyde with various aluminium alkoxides has been studied kinetically in benzene at 20°. The aluminium t-butoxide catalysed reaction shows a long induction period and gives benzyl benzoate (75–90%) together with a small amount of t-butyl benzoate and benzyl alcohol. The initial rate of reaction is decreased in the order: aluminium benzyl oxide > di-t-butoxyaluminium benzyloxide [a reaction mixture of PhCHOAl(O-t-Bu) 3 ] > aluminium isopropoxide > aluminium t-butoxide. The aluminium benzyloxide catalysed reaction is second-order in benzaldehyde. These results support a mechanism involving an alkoxide transfer from catalyst to aldehyde. A t-butoxide transfer to benzaldehyde is much slower than the benzyloxide transfer because of a large steric interaction between bulky t-butoxide and benzene ring. On the contrary, hydride transfer is rate-determining with aluminium benzyloxide. Electron-withdrawing substituents of aldehyde promote the Tishchenko reaction. Crossed Tishchenko reaction is discussed in terms of the alkoxide transfer and the hydride transfer.

The effect of ligands on hydride transfer to a carbonyl group (Tishchenko reaction and Meerwein-Ponndorf reduction) caused by ButOCu complexes is described.

The effect of ligands on hydride transfer to a carbonyl group (Tishchenko reaction and Meerwein-Ponndorf reduction) caused by ButOCu complexes is described.