Radicals from fragmentation of benzyloxymethoxycarbenes in solution

Abstract

2-Benzyloxy-2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazolines, including the parent as well as p-substituted analogues, undergo thermolysis at 100°C in benzene to afford a mixture of products. Two primary fragmentations of the oxadiazolines were identified. The major pathway involves 1,3-dipolar cycloreversion to N2 and the corresponding carbonyl ylides. The latter dissociate to acetone and the corresponding benzyloxy(methoxy)carbenes, which undergo fragmentation to ArCH2 and MeOCO radical pairs that recombine to afford methyl arylacetates. Carbene dimers were not observed, showing that the fragmentation process is faster than carbene dimerization. A second fragmentation pathway observed for the oxadiazolines is an alternative cycloreversion to the corresponding benzyl methyl carbonate and 2-diazopropane. Products from diazopropane included acetone azine and, in some instances, traces of propene.Key words: benzyloxy(methoxy)carbene, carbene, radical pair, rearrangement.

Synthesis of Ketones and Esters from Heteroatom-Functionalized Alkenes by Cobalt-Mediated Hydrogen Atom Transfer

“…19 F NMR (375 MHz, CDCl 3 ) δ −62.6. 1 H and 13 C NMR data for methyl 2-(4-(trifluoromethyl)­phenyl)­acetate ( 12h ) prepared in this way were in agreement with those previously described …”

“…1 H and 13 C NMR data for methyl 2-(4-(trifluoromethyl)phenyl)acetate (12h) prepared in this way were in agreement with those previously described. 58 Hydrolysis of 1-(2,2-Dibromovinyl)naphthalene (11k; Table 3, Entry 11). Following general procedure A using 1-(2,2-dibromovinyl)naphthalene (11k, 78.0 mg, 250 μmol, 1 equiv).…”

Investigation of the mechanism of 1,2-migrations in methoxysiloxycarbene with the electron localization function

“…10 Similar findings have been reported recently for p-substituted benzyloxy(methoxy)carbenes 11 and benzyloxy(benzyloxy)carbenes. 12 Methoxytriphenylsiloxycarbene generated from an oxadiazoline precursor in benzene at 110 o C was recently reported to rearrange by 1,2-triphenylsilyl migration from oxygen to the carbene carbon, yielding methyl triphenylsilylformate.…”

Probing the Nature and Extent of Stabilization within Foiled Carbenes: Homoallylic Participation by a Neighboring Cyclopropane Ring

“…The compound was identified by scaling up the reaction of the thermolysis of 6b in pentane, which gave 11 in an isolated yield of 11%. The azine can derive either from the reaction of carbene 3 with diazo compound 10 , which is formed by the loss of methyl acetate from oxadiazoline 6, or from a bimolecular reaction of 10 with itself followed by the loss of N 2 (Scheme b) . These processes can occur simultaneously wherein the dominating one depends on the solution’s concentration.…”