The Generation of 2,2-Diphenyldiazocyclopropane and 2,2-Diphenylcyclorppylidene from the Thermal decomposition of N-Nitroso-N-(2,2-diphenylcyclopropyl)-urea

Jones, W. M.; Grasley, Michael H.; Baarda, D. G.

doi:10.1021/ja01059a035

Cited by 14 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Alienes are also formed when diazocyclopropanes decompose, and kinetic data suggest that at least some of the aliene forms from an intermediate carbene (290)(291)(292)294). Other reactions in which alienes are formed in small amounts, and which may involve cyclic carbene intermediates, are the photolysis of carbon suboxide with olefins (41, 391), the interaction of "hot" carbon atoms with ethylene (350,358), the reactions of methylene with ketene (144) and acetylene (276), and the thermal decomposition of triphenylcyclopropylidenephosphorane (60).…”

Section: From Dihalocyclopropanesmentioning

confidence: 99%

The Chemistry of Allenes

Taylor¹

1967

Chem. Rev.

253

View full text Add to dashboard Cite

Section: From Dihalocyclopropanesmentioning

confidence: 99%

The Chemistry of Allenes

Taylor¹

1967

Chem. Rev.

253

View full text Add to dashboard Cite

Thermal Rearrangements of 2-Vinylcyclopropylidene to Cyclopentadiene and Vinylallene: A Theoretical Investigation

Olivella

López

2001

Chem. Eur. J.

View full text Add to dashboard Cite

In an attempt to clarify the favored rearrangement reaction of vinylcyclopropylidenes, the prototype thermal rearrangements of singlet 2-vinylcyclopropylidene (1) leading to 1,3cyclopentadiene (2) and 1,2,4-pentatriene (vinylallene) (3) were investigated by means of ab initio quantum-mechanical electronic-structure calculations. The B3LYP functional with the 6-31G(d) basis set was employed for geometry optimization of the equilibrium and transition-state structures relevant to the two reaction pathways and for computing their harmonic vibrational frequencies. Final energies were evaluated by single-point calculations at the CCSD(T) level of theory with the 6-311 + G(3df,2p) basis set. The rearrangement of s-cis 1 to 2 is found to occur by a three-step pathway. The first step involves the formation of a nonclassical carbene (5), which is an internal pi complex between the pi molecular orbital of the double bond and the empty p atomic orbital of the carbene carbon. In the second step, the nonplanar five-membered ring geometry of 5 flattens to reach the planar structure of 3-cyclopentenylidene (4). The last step is the 1,2-migration of a alpha-hydrogen atom to the carbene center in 4. The rate-determining step for the rearrangement of s-cis 1 to 2 is the formation of 5, with a predicted global deltaG++(220 K) of only 0.6 kcalmol(-1). The rearrangement of s-trans 1 to 2 requires an initial conversion of s-trans 1 to the s-cis conformer, with a predicted deltaG++(220 K) of 1.8 kcalmol(-1). The transition structure for the ring-opening of s-trans 1 into s-trans 3 (deltaG++(220 K)=4.7 kcalmol(-1)) is more energetic than that for the ring-opening of s-cis 1 into s-cis 3 (deltaG++(220 K)=2.5 kcalmol(-2)) due to larger repulsive nonbonded H...H interactions in the former transition structure. On the basis of these results, it is suggested that if the reaction of 1,1-dibromo-2-vinylcyclopropane with methyllithium at -78 degrees C leads to the initial formation of carbene 1, then the reaction should yield 2 as the main product together with small amounts of 3. This theoretical prediction nicely agrees with experimental findings.

show abstract