[7270-63-5]  · C6H6N2O4  · 5-Diazo-2,2-dimethyl-1,3-dioxane-4,6-dione  · (MW 170.14)

(reagent for the synthesis of a-oxygenated ketenes for [2 + 2] cycloadditions with alkenes2)

Alternate Name: diazo Meldrum's acid.

Physical Data: solid with a melting point of 90-91 °C.

Solubility: sol ether, dichloromethane, and acetonitrile.

Preparative Methods: most commonly by diazo transfer to Meldrum's acid. A number of procedures involving the use of sulfonyl azide reagents have been reported.1 Typical procedures involve the addition of the sulfonyl azide to a solution of Meldrum's acid containing a tertiary amine base. Aqueous workup followed by chromatography on silica gel provide the diazo compound in yields ranging from 40 to 76%. A modification using KF on alumina is reported to provide a 90% yield of product.1a Diazo compounds are potentially explosive as are certain sulfonyl azides, such as tosyl azide. For this reason, extreme care must be observed in the synthesis and use of this compound, with all operations being conducted behind a blast shield in a fume hood.

Handling, Storage, and Precautions: in addition to the previously mentioned explosion hazard which this reagent presents, there are health related hazards that must also be considered. Diazo compounds, as a class, are toxic and irritating and can be sensitizers. They must be used in a well-ventilated fume hood and not come in contact with skin. For a description of the hazards associated with this class of compounds, see the handling and storage precautions listed for Diazomethane.


Diazo Meldrum's acid was at one time used for the synthesis of spiro activated cyclopropanes;2 however, after the original report, it was found that the adduct formed was not the expected cyclopropane, but a cyclobutane which was the result of ketene-alkene cycloaddition.3 Thus photolysis at 254 nm promotes extrusion of N2 to provide a carbene which undergoes a Wolff rearrangement to provide an a-alkoxy ketene. This then undergoes a [2 + 2] cycloaddition to provide the cyclobutane (eq 1). This reaction appears to work with a variety of alkenes including hindered alkenes such 1,3,3-trimethylcyclohexene (eq 2).

Related Reagents.

Dimethyl Diazomalonate; Ethyl Diazoacetate; Methyl Diazoacetate.

1. (a) Alloum, A. B.; Villemin, D. SC 1989, 19, 2567. (b) Baum, J. S.; Shook, D. A.; Davies, H. M. L.; Smith, H. D. SC 1987, 17, 1709. (c) Rao, Y. K.; Nagarajan, M. IJC(B) 1986, 25B, 735. (d) Hazen, G. G.; Weinstock, L. M.; Connell, R.; Bollinger, F. W. SC 1981, 11, 947. (e) Regitz, M.; Stadler, D. LA 1965, 687, 214. (f) Eistert, B.; Geiss, F. CB 1966, 99, 3128.
2. Livinghouse, T.; Stevens, R. V. JACS 1978, 100, 6479; Livinghouse, T.; Stevens, R. V. CC 1978, 754; Stevens, R. V. PAC 1979, 51, 1317.
3. Stevens, R. V.; Bisacchi, G. S.; Goldsmith, L.; Strouse, C. E. JOC 1980, 45, 2708.

Tarek Sammakia

University of Colorado, Boulder, CO, USA

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