Dimethyl diazomalonate reaction with benzaldehyde

The reaction of dimethyl diazomalonate with an excess of benzaldehyde with or without metal catalyst furnished the diastereomeric 1,3-dioxolanes (156) and the oxirane (155 Scheme 35). The reaction was proposed to proceed via the intermediacy of a carbonyl ylide dipole.135 Benzaldehyde plays a double role... 

Transition-metal mediated carbene transfer from 205 to benzaldehyde generates carbonyl ylides 211 which are transformed into oxiranes 216 by 1,3-cyclization, into tetrahydrofurans 212, 213 or dihydrofurans 214 by [3 + 2] cycloaddition with electron-deficient alkenes or alkynes, and 1,3-dioxolanes 215 by [3 + 2] cycloaddition with excess carbonyl compound120 (equation 67). Related carbonyl ylide reactions have been performed with crotonaldehyde, acetone and cyclohexanone (equation 68). However, the ylide generated from cyclohexanone could not be trapped with dimethyl fumarate. Rather, the enol ether 217, probably formed by 1,4-proton shift in the ylide intermediate, was isolated in low yield120. In this respect, the carbene transfer reaction with 205 is not different from that with ethyl diazoacetate121, whereas a close analogy to diazomalonates is observed for the other carbonyl ylide reactions. 

Only a limited number of examples have been reported. The reactivity of sulfonium ylide 98a, prepared by the reaction of thiepine 96 and dimethyl diazomalonate (Section 13.03.6.1), was examined <20060BC2218>. The reactivity of the stabilized sulfonium ylide 98a was restricted to the highly reactive Michael acceptor, tetracya-noethylene 152 (the ylide failed to react with benzaldehyde or dicyanoethylene). Reaction of ylide 98a with tetracyanoethylene 152 led to the consumption of the ylide 98a (Equation 22). Thiepine 96 was produced in the reaction and the formation of cyclopropane 153 was suggested. 

The mechanism of the reaction between dimethyl diazomalonate with an excess of benzaldehyde has been shown to proceed via carbonyl ylide (57) 1 ylide undergoes either electrocyclic ring closure to (58) or further reaction... 

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