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Isopropylidene malonate is an important reagent in synthetic chemistry and involved in the formation of new C-C bonds, rings, amides, esters, and acids. The presence of carbonyl groups at C-4 and C-6 positions favors the alkylation and acylation reactions due to its acidic nature. It is also employed as an antimicrobial agent. It is used in the preparation of 4-pyridyl-substituted heterocycles, 2-substituted indoles, isofraxidin and macrocyclic beta-keto lactones. Further, it is involved in the Knoevenagel condensation reaction with aldehydes.
Malonate ester which is an unusually strong acid (pKa = 9.97) in comparison with, e.g. Diethyl malonate, A15468 : J. Am. Chem. Soc., 70, 3426 (1948). The mild conditions required for alkylation, acylation, etc. and the ease with which the products undergo alcoholysis or hydrolysis-decarboxylation make Meldrum's acid a valuable and versatile synthetic intermediate. Reviews: Chem. Soc. Rev., 7, 345 (1978); Heterocycles, 32, 529 (1991); Synlett, 1649 (2004).
For phase-transfer alkylation using K2CO3 as base, see: Synthesis, 452 (1982); Bull. Soc. Chim. Belg., 104, 643 (1995). Phase-transfer addition to Michael acceptors also occurs: Synthesis, 224 (1984). Mitsunobu dialkylation with an alcohol and DIAD/Ph3P is also possible: J. Org. Chem., 62, 1617 (1997).
Knoevenagel condensation with aldehydes gives ylidene derivatives which are solvolyzed by alcohols to give monoesters of alkylidene or arylidene malonic acids: J. Am. Chem. Soc., 74, 5897 (1952). For diastereoselective condensation with citronellal, followed by intramolecular Diels-Alder reaction, see: Org. Synth. Coll., 8, 353 (1993). With formaldehyde in pyridine gives the stable pyridinium methylide which, on treatment with acid, generates the useful reactive Michael acceptor and dienophile, methylene Meldrum's acid: Synthesis, 215 (1996).
With an aryl aldehyde in the presence of triethylamine and formic acid at ambient temperature, in situ reduction to the arylmethyl Meldrum's acid occurs, whereas at 70-80oC, the 3-arylpropionic acid is obtained: Synth. Commun., 25, 3067 (1995).
C-Acylation with acyl chlorides occurs in the presence of 2 equivalents of pyridine in high yield. Alcoholysis of the product provides a good route to ß-keto esters: J. Org. Chem., 43, 2087 (1978); Org. Synth. Coll., 7, 359 (1988), also obtainable by reaction of the Na salt with acid anhydrides in DMF: Synthesis, 451 (1982). Alternatively, mild hydrolysis and decarboxylation of the intermediate acyl Meldrum's acid gives the methyl ketone, providing an alternative to organometallic methods for conversion of acyl chlorides to methyl ketones: Synth. Commun., 10, 221 (1980):
See also: Org. Synth., 77, 114 (1999).
Condensation with lactim ethers, catalyzed by Nickel(II) 2,4-pentanedionate, 18811 , with alcoholysis of the resulting enamino Meldrum's acids, gives of cyclic ß-enamino esters, useful as alkaloid precursors: J. Org. Chem., 43, 4662 (1978); for an example, see: Org. Synth. Coll., 8, 263 (1993).
Kohl, F.; Schmitz, J.; Furtmann, N.; Schulz-Fincke, A. C.; Mertens, M. D.; Küppers, J.; Benkhoff, M.; Tobiasch, E.; Bartz, U.; Bajorath, J.; Stirnberg, M.; Gütschow, M. Design, characterization and cellular uptake studies of fluorescence-labeled prototypic cathepsin inhibitors. Org. Biomol. Chem. 2015, 13 (41), 10310-10323.
Häußler, D.; Gütschow, M. Synthesis of a Fluorescent-Labeled Bisbenzamidine Containing the Central (6, 7-Dimethoxy-4-coumaryl) Alanine Building Block. Heteroat. Chem. 2015, 26 (5), 367-373.
Hazard Statements: H315-H319-H335
Causes skin irritation. Causes serious eye irritation. May cause respiratory irritation.
Precautionary Statements: P261-P280a-P305+P351+P338-P304+P340-P405-P501a
Avoid breathing dust/fume/gas/mist/vapours/spray. Wear protective gloves and eye/face protection. IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. IF INHALED: Remove to fresh air and keep at rest in a position comfortable for breathing. Store locked up. Dispose of contents/container in accordance with local/regional/national/international regulations.