Alkyl pyruvates

Pyruvic acid is the simplest homologue of the a-keto acid, whose established procedures for synthesis are the dehydrative decarboxylation of tartaric acid and the hydrolysis of acetyl cyanide. On the other hand, vapor-phase contact oxidation of alkyl lactates to corresponding alkyl pyruvates using V2C - and MoOa-baseds mixed oxide catalysts has also been known [1-4]. Recently we found that pyruvic acid is obtained directly from a vapor-phase oxidative-dehydrogenation of lactic acid over iron phosphate catalysts with a P/Fe atomic ratio of 1.2 at a temperature around 230°C [5]. 

CH3CH=C=C (2). Both reagents react with alkyl pyruvates to... 

Diastereoselective reactions with alkyl pyruvates. The reagent (1) reacts with pyruvates to form the an/i-substituted derivatives (2) selectively. The corresponding reaction with 2-butenyltributyltin in combination with BF, shows slight diastereoselectivity. 

Asymmetric reduction of a-keto esters.3 Alkyl pyruvates are rapidly reduced by this borane to alkyl (S)-lactates (equation I). The extent of asymmetric induction depends to some extent on the temperature and the size of the ester group. Quantitative optical... 

An electron transfer mechanism has been proposed to account for the formation of carbon dioxide on irradiation of alkyl pyruvates the yield of carbon dioxide is enhanced by the presence of electron acceptors such as methyl viologen. The dye-sensitized photo-oxidation of a-oxo-carboxylic acids and esters also leads to the production of carbon dioxide. An initial dye-substrate interaction rather than singlet oxygen appears to be responsible for this fragmentation. 

Since the formation of cyclic pyruvate acetals from alkyl pyruvates and diols under classical conditions (i.e. catalysis by acids) is expected to be unfavoured due to the necessity of the intermediate formation of a destabilized carbocation, early attempts to prepare 1-carboxyethylidene sugars used indirect procedures. Later, it was shown that under carefully controlled conditions the direct acetalation of a sugar diol with methyl pyruvate can also be used for preparative purposes. 

Hydrogenation of alkyl pyruvates to their corresponding lactates have received considerable attention both from a theoretical and experimental standpoint. Some example results are shown in Table 9.3. Enantioselectivity in these systems is measured in terms of enantiomeric excess (ee) which is defined as ([R] - [S])/([R] + [S]). 

Phosphoroisocyanatidites (e.g. 83) react with 3-alkylidene-2,4-pentanediones (e.g. 84a) or 2-alkylideneacetoacetic esters (e.g. 84b) to form phosphoranes (85,a,b) which decompose on heating to the cyclic phosphonates (86a, b)27. in an analogous study, dialkylalkynylphosphonates (87) have been shown to react with alkyl pyruvates (88) below 0°C to form mixtures of alkynyl phosphonates (90) and monocyclic tetraoxaphosphoranes (91) via (89)28. At 80°C, however, (89) reacts with excess (88) via (92) to form the bicyclic phosphorane (93). 

The synthetic potential of lanthanide catalysis has been recognized in high pressure chemistry mainly during the last decade although earlier work was concerned with the beneficial effect of the biactivation mode to overcome steric hindrance in hetero-Diels-Alder reactions [30]. In this way, alkyl pyruvates and aldehydes considered as dienophiles could react with 1-methoxy-l,3-butadiene yielding adducts which could serve as synthons in sugar synthesis [31]. 

Hydrogenation of alkyl pyruvates (Fig. 5.10) to their corresponding lactates has received considerable attention both from a... 

CATALYTIC ASYMMETRIC REDUCTION via HYDROSILYLATION OF ALKYL PYRUVATES AND ETHYL BENZOYLFORMATE [55]... 

Thalhammer, R, Schrank, K.H., Wernthaler, K., 1999. Preparation of Alkyl Pyruvate Derivatives, Cost Effective and Suitable for Plant Scale Production, DE patent 19756584 Al. 

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