97073-41-1

Upstream product

• 592-41-6 1-hexene 
• 88211-05-6 3-benzyl-3-chloro-3H-diazirine 
• 563-79-1 2,3-Dimethyl-2-butene 
• 88211-07-8 Benzylchlorocarbene 

Relevant academic research and scientific papers

Generation and study of benzylchlorocarbene from a phenanthrene precursor

The curved plots of (carbene adduct)/(carbene-rearrangement product) versus carbene trapping agent, tetramethylene [TME], reported with benzylchlorodiazirine 1 have been reproduced. However, with the use of a non- nitrogenous precursor, plots of this type are approximately linear over the range of [TME] employed. Thus, any complex formed between benzylchlorocarbene and TME must collapse to form cyclopropane faster then it can fragment with rearrangement to β-chlorostyrene and TME. Diazirine 1 does photoisomerize to diazo compound 7, but this process is inefficient (φ = 0.075) and is not likely to be responsible for the curvature in plots of adduct/styrene versus [TME] observed with the diazirine precursor. Thus, the second, noncarbene, pathway to β-chlorostyrene is neither a carbene-olefin complex nor a diazo intermediate. It is proposed that the second pathway involves a rearrangement in the excited state of the diazirine, although other explanations cannot be discarded.

Rearrangement of alkylchlorocarbenes: 1,2-H shift in free carbene, carbene-olefin complex, and excited states of carbene precursors

Photolysis of alkylchlorodiazirines (1) in the presence of olefins gives a cyclopropane (3) by addition of the generated carbene to the olefin and a vinyl chloride derivative (2) resulting from a 1,2-H shift rearrangement. This rearrangement may occur either in the carbene or in some excited state, precursor of the carbene (RIES mechanism), or in a 'carbene + olefin complex' on the way to the formation of 3 (COC mechanism). Results obtained by time-resolved photoacoustic calorimetry as well as by thermolysis and photolysis of ClCH2C(N2)Cl and CH3(CH2)2C(N2)Cl in the presence of tetramethylethylene clearly indicate that both the RIES and COC mechanisms play a role but with efficiencies which greatly depend on the nature of the diazirine. Reexamination of the results previously obtained with benzylchlorodiazirines indicates that, for this class of diazirines, the RIES mechanism is temperature dependent and has a very low efficiency at room temperature and below, whereas the nonlinearity of the plots [3]/[2] vs [olefin] is mainly due to the COC mechanism.

Benzylchlorocarbene: Kinetics parameters for 1,2-H migration, UV absorption spectrum, and mechanism for addition to alkenes

Laser flash photolysis (LFP) of 3-benzyl-3-chlorodiazirine, 1, in isooctane, produces benzylchlorocarbene which reacts with pyridine to form an ylide or undergoes 1,2-H migration to form the (Z)- and (E)-β-chlorostyrenes. The rate for the 1,2-H migration is determined by plotting the pseudo-first-order rate constants for the growth of the ylide vs [pyridine] and extrapolating to [pyridine] = 0. From such measurements, performed at various temperatures, the kinetic parameters Ei = 4.5 kcal/mol and Ai = 1011.1 s-1 are obtained, LFP of 1 in the absence of pyridine produces a transient absorption (280-330 nm) assigned to benzylchlorocarbene. Monitoring the carbene decay directly at 310 nm over the same temperature range gives similar values: Ei = 4.8 kcal/mol and Ai = 1011.3 s-1. Three independent methods-LFP, products ratios (Z/E and cyclopropane/chlorostyrenes) - yield a single value, (6.2 ±0.2) 108 M-1 s-1 for kt, the rate constant for the addition of benzylchlorocarbene to tetramethylethylene. These results are consistent with a mechanism involving the formation of a complex between benzylchlorocarbene and tetramethylethylene.

Benzylchlorocarbene: A New Ambiphile

Relative reactivites of benzylchlorocarbene towards electron-poor and electron-rich alkenes indicate the carbene to be ambiphilic.

Thermolysis and Photolysis of 3-Chloro-3-benzyldiazirines in Alkenes: Evidence for a Carbene-Alkene Complex

Photolysis and thermolysis of substituted 3-chloro-3-benzyldiazirines in alkenes yielded cyclopropanes and chlorostyrenes as products.The results suggest that the cyclopropanation of benzylchlorocarbenes is independent of substituents.However, 1,2-hydrogen migration is accelerated by OCH3 or CH3 substituents, and is decelerated by a Cl substituent on the phenyl ring.These results support the existence of an energy barrier to 1,2-H migration.Evidence is provided for carbene-alkene complexation.

Energy Barrier for 1,2-Hydrogen Migration in Benzylchlorocarbene

The intermolecular-intramolecular rate constants derived from the thermolysis and photolysis of 3-chloro-3-benzyldiazirine in tetramethylene gave an excellent Arrhenius plot; an activation energy of 6.4 kcal mol-1 (26.8 kJ mol-1) was obtained for the 1,2-H migration in benzylchlorocarbene.

REACTIVE INTERMEDIATES IN THE PHOTOLYSIS AND THERMOLYSIS OF 3-CHLORO-3-BENZYLDIAZIRINE

The photochemical and thermal decomposition of 3-chloro-3-benzyldiazirine have been studied in different reaction conditions.The decomposition gives rise to benzylchlorocarbene which can rearrange to E and Z chlorostyrene and/or react with the environment.In the presence of acetic acid the main product is 1-chloro-2-phenylethyl acetate.Experiments with acetic acid-d4 showed that some of the chlorostyrene is formed from the carbocation; other experiments conducted with tetramethylethylene as a carbene trapping agent show that the carbene is formed even in the presence of acetic acid.