Malonyl dichloride

Malonyl dichloride has been prepared from malonic acid and thionyl chloride,4-9 and from carbon suboxide and anhydrous liquid hydrogen chloride.10 This procedure is based on that of Staudinger and Bereza 6 and of Backer and Homan.8... 

Di-fer -butyl malonate has been prepared by the reaction of malonyl dichloride and fer/-butyl alcohol in the presence of a base,8,11 and of malonic acid with isobutylene in the presence of sulfuric acid.3 The present procedure was based on the former method and developed from studies initiated by P. C. Mukharji of the University College of Science and Technology, Calcutta. 

Malonyl dichloride, 33, 20 2-Mercaptobenzimidazole, 30, 56 2-Mercaptobenzoxazole, 30, 57 Mercuric cyanide, 32, 31 Methallyl chloride, 32, 90 MeTHANEPHOSPHORIC ACID, DnSOPRO-PYL ESTER, 31, 33 Methanesulfonic acid, 30, 58 Methaneshlfonyl chloride, 30, 58 Methanol, 30, 31 32, 79 Methone, 31, 40... 

Malonic ester syntheses, 30, 7 Malononitrile, 37, 53 Malonyl dichloride, 33, 20 Mandelic acid, 36, 3 Mandelic acid, />-bromo, 35,11 Mannich reaction, with acetone, 37,18 Mercaptoacetaldehyde, diethyl ACETAL, 35, 51... 

Diesters are malonates, and are often used for the synthesis of barbiturates. Malonyl dichlorides can be used in place of a malonyl diesters, in which case the reaction can be performed at room temperature, as demonstrated by the synthesis of A-phenyl and A -pyridyl 2-thiobarbituric acids 666 from malonyl dichloride 664 and A, iV -diarylureas 665 <2002AJC287>. 

In 1998, Evans published an improved synthesis of bu-box 3 starting from the same amino acid. The updated synthesis began with sodium borohydride-iodine reduction to afford amino alcohol 23 followed again by treatment with dimethyl-malonyl dichloride 24 to afford 25 in 88% yield (from 23). Cyclization was achieved by treatment of 25 with toluenesulfonyl chloride and triethylamine in the presence of a catalytic amount of dimethylaminopyridine to afford bu-box 3 in 82% yield (Fig. 9.6). 

The base-catalyzed self-condensation of diketene is a similar type of reaction and yields dehydroacetic acid together with the tripyranone (322) (49JOC460, B-68MI22400). Ring opening of diketene and attack of the oxyanion on a second molecule of diketene followed by an intramolecular condensation accounts for the formation of the pyranone. The selfcondensation of malonyl dichloride in the presence of a ketone, which acts as a weak base, is a similar reaction (52JCS4109). 

The reaction of ethyl acetoacetate with malonyl dichlorides has been used to synthesize a range of substituted 4-hydroxypyran-2-ones (58CB2849). Yields and purity of the products were best using benzene as solvent either without a catalyst or using magnesium acetate in this role. Hydrolysis of the C-5 ester function and subsequent decarboxylation are both feasible. 

Diketones are converted into pyranones on treatment with malonyl dichloride, involving both C- and O-acylation (63JCS4483). The reaction between benzoylacetone and the acid chloride gives only one pyranone in accordance with a preferred direction of enolization consequent upon the unsymmetrical nature of the diketone a 5-acetyl-6-phenylpyranone results rather than the 5-benzoyl-6-methyl isomer. There is still some uncertainty as to whether the product is the 4-hydroxypyran-2-one (409) or the tautomer, but the former is considered to be the more likely. There is yet further controversy, since... 

Catalyzed carbonylation (CO) reactions lead to formation of either chloroacelyl chloride or malonyl dichloride. 

Malonyl dichloride furnishes 2-aryl-5,6-dihydro-4//-l,3-thiazine-4,6-diones (4) (68USP3408348). The condensation of carbon suboxide, C302, with arenethiocarboxamide also leads to thiazinediones (4) or 4-hydroxy-6//-l,3-thiazine-6-ones (5) (Scheme 4) (62M26 64M1061). 

Phloroglucinols Malonyl dichloride reacts with keto enol ethers to form phlo-roglucinols (2) and/or 4-hydroxy-2H-pyran-2-ones (3), which are readily convertible into phloroglucinols. 

Chromium carbene complexes. phloroglucinols Malonyl dichloride. phthalides Thallium(III) trifluoroacetate. pinacols Samarium(II) iodide. Tetra-w-butylammonium fluoride. 

Preparation from malonic acid, isobutene, and a catalytic amount of coned, sulfuric acid in ether at a pressure of about 40 p.s.i. " Preparation via malonyl dichloride the first step requires heating at 45-50° for 3 days. 

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