Electrochemical synthesis of pentamethylenediazirine

Abstract

Electrochemical synthesis of pentamethylenediazirine at the Pt/Ti anode was conducted. The reaction is reversible. The rate constants of the direct and reverse processes were estimated. The product and current yields of the target compound approach to 100%.Diazirines are efficient sources of carbenes. 1 For in stance, photolysis of pentamethylenediazirine 1 under high pressure affords cyclohexene 2 in high yield (Scheme 1). 2 Scheme 1Usual methods for the synthesis of diazirines are the oxidation of the corresponding diaziridines with mercury oxide, bichromate, silver oxide, and others.In the present work, compound 1 was synthesized by the electrochemical oxidation of pentamethylenedi aziridine 3 (Scheme 2). 3,4 Scheme 2The oxidation products of compound 3 in an undi vided cell using the Pt/Ti anode were analyzed by 1 H, 13 С NMR and UV spectroscopy. The analysis showed that the oxidation of compound 3 affords up to 50% of compound 1 without formation of by products. The UV spectra of the electrolyte containing a mixture of com pounds 1 and 3 coincided with the published 5 spectra of compound 1. The UV spectra of a solution of compound 3 oxidized in an undivided cell upon passing different amounts of electricity are shown in Fig. 1. When the content of compound 1 increases monotonically, the con tent of compound 3 decreases, correspondingly, to some limiting value (Fig. 2) equal approximately to 50%, which can be due to reversibility of the process in an undivided cell. This conclusion was completely confirmed by the electrolysis of the initial compound in a diaphragm di vided cell loaded with a mixture of equal amounts of compounds 1 and 3. In the presence of a diaphragm, the initial substrate in this mixture can be oxidized with al most 100% conversion, i.e., until the initial substrate dis appeared completely (Fig. 3).Using the data presented in Fig. 3, we estimated the rate constant of substrate oxidation in the direct path way (k) by the first order equationwhere С 0 and С t are the initial concentration of com pound 3 and its concentration to the moment t. The k value was 0.12 h -1 . The curve for the consumption of compound 3 calculated by the first order equation with k = 0.12 h -1 is shown in Fig. 3. Since in the absence of a diaphragm and in equilibrium the contents of the initial * Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday.