The Synthesis of Dichlorodiazirine and the Generation of Dichlorocarbene:  Spectroscopy and Structure of Dichlorocarbene Ylides

Abstract

Reaction of 2,4-dinitrophenoxychlorodiazirine (13) with chloride ions affords dichlorodiazirine (4). Photolysis of 4 generates dichlorocarbene. In laser flash photolysis (LFP) experiments, CCl2 forms chromophoric ylides or oxides with pyridine, 2-picoline, thioanisole, and oxygen. Spectroscopic and computational studies of the ylides are reported. The UV spectrum of CCl2 in solution, however, is not observed. It appears possible that CCl2 is rapidly captured by oxygen to afford a chromophoric dichlorocarbene carbonyl oxide. We present a theoretical analysis of this process.

Enthalpy versus Entropy in Chlorocarbene/Alkene Addition Reactions

“…7a-c Jorgensen also predicted entropic control for CCl 2 additions but computed an enthalpic barrier of 1.1 kcal/mol for its addition to ethene, based on MP2/6-31G(d) calculations. 7d Our syntheses of dichlorodiazirine 8 (1) and chlorofluorodiazirine 9 (2) afford spectroscopy-friendly precursors for CCl 2 and CClF which allow the LFP acquisition of kinetic data. Now, we report the first activation parameters for additions of these carbenes to alkenes, permitting us to evaluate some of the foregoing vintage predictions.…”

Dihalodiazirines and the photochemical generation of dihalocarbenes: new light on old problems

“…A successful approach features the conversion of R in diazirine 8 into a leaving group . Our preparation of dichlorodiazirine (DCD, 6 ) is outlined in Scheme , and begins with the Graham oxidation of phenylisourea mesylate ( 12 ) to phenoxychlorodiazirine ( 13 ) 35, 36. Dinitration of 13 with nitronium tetrafluoroborate in nitromethane then provides 2,4‐dinitrophenoxychlorodiazirine ( 14 ), in which the diazirine's ‘R’ group has been transformed into a leaving group.…”

Carbenes and Nitrenes

“…The same group reported a full study of the generation of dichlorocarbene. 28 Again, full details on the preparation of its diazirine precursor and also spectroscopic studies of dichlorocarbene ylides, corroborated by DFT calculations, were given.…”

“…In contrast, copper-bisoxazoline complexes ee very efficiently catalysed the O-H insertion on phenol yielding α-aryloxypropionate (27). 58 The reaction proved highly enantioselective when spirobox (28) was used as a ligand.…”