Thermolysis and photolysis of arylchlorodiazirines in allyl bromide

Cyclopropanation of Alkenes with Halodiazirines as Halocarbene Precursors in Continuous Flow

“…Importantly, when a lower yield was obtained, e. g. in the reaction of 3-(chloro)-3-(4-chlorophenyl)-3H-diazirine 1 b with various alkenes leading to 2 bb-2 be, no by-products could be identified, e. g. the corresponding azine or dimeric 1,2-dichloro-1,2-diarylethene which were isolated in thermolysis and photolysis conditions. [30] Notably, when diazirine 1 a was reacted with dimethyl maleate in the same conditions, only a very low yield of corresponding cyclopropanes was obtained (less than 9 %, with no traces of any trans-diastereoisomer). [31] This result seems in line with the stabilization of the singlet state of these halocarbenes leading to a stereospecific reaction.…”

Halodiazirines as Valuable Reagents for the Synthesis of Halocyclo­propanes

“…The formation of this side product was rationalized by the attack of the carbene on the bromine atom to generate a brominium ylid followed by an intramolecular allylic rearrangement. 12 Scheme 5 Thermolysis and photolysis of arylchlorodiazirines with allyl bromide…”

“…In 1994, Bonneau et al reported the synthesis of chlorocyclopropanes from the reactions of various arylchlorodiazirines with allyl bromide (Scheme 5 ). 12 An azine was also formed as a by-product when p -chlorophenylchlorodiazirine was used. 12 It was suggested by the authors that the cycloaddition of the corresponding carbene with allyl bromide is a slow reaction.…”

“…12 An azine was also formed as a by-product when p -chlorophenylchlorodiazirine was used. 12 It was suggested by the authors that the cycloaddition of the corresponding carbene with allyl bromide is a slow reaction. In the case of p -nitrophenylchlorocarbene, a small amount of insertion product was also afforded in addition to the cyclopropanes.…”

“…The formation of this side product was rationalized by the attack of the carbene on the bromine atom to generate a brominium ylide followed by an intramolecular allylic rearrangement. 12 The reaction of C 60 with an equimolar amount of chlorophenyldiazirine in refluxing toluene afforded a C 60 -chlorophenylcarbene 1:1 adduct (Scheme 6). 13 The [6,6] adduct to C 60 was shown to possess the cyclopropane structure and was obtained in a moderate yield.…”