Carbon suboxide, reaction

Carbon suboxide —, reactions with — 17, 652 —, ring closures to heterocyclics 17, 652 Carbonyiation —, aldehydes by — 17, 729 Carbonyl chloride s. Phosgene... 

Liquid carbon suboxide added to a solution of 2-ethylaminothiarole in anhydrous ether at 0°C gives immediate formation of a white precipitate of the mesoionic xanthine (121) (R=H) (130), otherwise prepared by reaction between 2-ethylaminothiazole and phenoxycarbonyl isocyanate (see p. 65 and Ref. 304),... 

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

Figure 3-14 shows an induction period in the reaction of carbon suboxide (O=C=C=C=0) with triethylamine. This reaction is complex and is not yet... 

Figure 3-14. Absorbance-time plots for the reaction of carbon suboxide and triethylamine in ether solution in the presence of acetic anhydride. The initial C3O2 concentration was 2.03 X I0 - M the amine concentrations were 3 X lO " M, 5 x 10 M, and 7 X lO " M.

Published sources do not mention any dangerous reactions with carbon suboxide, which is hardly ever used. 

The first synthesis of derivatives (77) of pentatetraene-carboxylic acid has been reported using a Wittig reaction of 1-H-allene-l,3-dicarboxylate monoester chlorides (76) in the presence of triethylamine.60 In one case an intermediate was obtained and was converted to (77) by further treatment with base. The reaction of carbon suboxide with phosphonium ylides has also... 

Reaction of urazoles 359 with carbon suboxide in dilute solutions (dioxane-MeCN 1 1, acetone, MeCN) provides 360, while in more concentrated solutions small yields (<25%) of 361 are also obtained (Scheme 54) <1995H(41)303>. 

Thiolactams 622 treated with carbon suboxide provide mesoionic compounds 623. Their 1,4-dipolar cycloaddition reaction with highly reactive PTAD gives compounds 624, formed by the cycloaddition followed by extrusion of COS, in quantitative yield (Scheme 100) <1995T6651, 1995H(41)1631>. 

Carbon Suboxide Photoiysis. In principle, carbon suboxide (1) can be used as a precursor to atomic carbon and two molecules of carbon monoxide as shown in Eq. 2. However, this reaction is endothermic by 141 kcal/mol and can only be realized in the vacuum ultraviolet (UV) at wavelengths that destroy most organic substrates. However, photolysis of 1 at 1470 A produces C atoms in a low-temperature matrix. The short wavelength flash photolysis of 1 coupled with atomic absorption has been used to measure the rate constants for various spin states of carbon with simple substrates. 

Carbonylcarbene reacts with oxetane in a complex manner, giving cyclopropane and propene by a deoxygenation process and ketene plus ethylene as apparent insertion-fragmentation products (equation 66). The reaction is carried out by irradiation of a solution of carbon suboxide in oxetane under these conditions, photodecomposition of intermediates is possible. The initial attack is believed to be at the ring oxygen atom to give a zwitterionic species (78JA6425). 

Ketene itself is commercially prepared in this manner. In a similar reaction, carbon suboxide is produced by heating malonic acid with P2Oj ... 

Dihydro-2//-pyrimido[2,l-a]isoquinoline-2,4-dione (93, R = R1 = H) was also prepared in the reaction of 1-aminoisoquinoline and carbon suboxide in diethyl ether in 10% yield (72CB108). 

A promising new method for the preparation of thiobarbituric acids (112) involving the reaction of carbon suboxide with various arylthio-ureas was reported by Baranova et al.2il... 

The heteroaromatic betaine (110) is formed in the reaction of 4,6-dimethyl-2-methyl-aminopyrimidine (234) with carbon suboxide (73JOC3485). 

The 2 + 2-cycloaddition reaction of a-alkoxyketene-derived imines yields /l-lactams with quaternary stereogenic centres at C(4).33 The 2 + 2-cycloaddition of chiral aminoketenes with chiral imines yields cis-fi-lactams with the absolute stereochemistry of file C(3) and C(4) positions being controlled by the ketene partner only.34 The 2 + 2-cycloaddition of ketenes with (W)-2-/-butyldihydrooxazole (19) yields predominately the regioisomer (20) from steric control rather than the expected electronic control (Scheme 7).35 The double 2 + 2-cycloaddition reaction between ketenylidenetriphe-nylphosphorane (21) and carbon suboxide (22) produces the bis(ylidic) spirocyclobut-anedione (23) (Scheme 8).36 Semiempirical and ab initio calculations have been used to investigate the Lewis acid-promoted 2 + 2-cycloaddition leading to the formation of jS-lactones.37... 

A very promising procedure deserves to be mentioned, the reaction of carbon suboxide (592) with hexamethyldisilazane (595)216 which affords in the first step 2,4-dioxo-6-trimethylsiloxy-l-TMS-l,2,3,4-tetrahydro-3-pyridine[N,N-bis(TMS)-car-boxamide] (395) or an isomer of 395 that can directly be converted to yield a variety of piperidine (397, 398, 400) and pyridine compounds (399a, 399b). 392 and 394... 

Hydroxy-2H-pyranones-2. These heterocycles are formed on reaction of si-lyl enol ethers with carbon suboxide in ether at — 20 - 250.1... 

Pyrimidino[l,5]diazepin-2,4-diones are formed by the treatment of 1,2-diaminopyrimidines with carbon suboxide <95H(4l)303>. The reaction may be extended to the formation of... 

The ground state C atoms are produced by the photolysis of carbon suboxide. They can be monitored by optical absorption at 1657 A. Reactions of C(3P) atoms with molecules have been studied by Husain and Kirsch (497,498) and Braun et al. (141). 

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