
TY  - JOUR
A1  - Crow, WD 
A1  - McNab, H 
T1  - Synthetic Applications of Intramolecular Insertion in Arylcarbenes. I. o-Alkylphenylcarbenes and 1-(o-Alkylphenyl)ethylidenes
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1979
VL  - 32
IS  - 1
SP  - 89
EP  - 98
KW  - 
UR  - https://doi.org/10.1071/CH9790089 
N2  - A series of phenylcarbenes and 1-phenylethylidenes, substituted in the ortho-position by alkyl chains of 1-4 carbon atoms, has been generated in the gas phase and pyrolysed at 250-750&#176;/0.05-0.10 mm. Apart from o-tolylcarbene, the phenylcarbenes show efficient insertion to form five- and six-membered rings, the former predominating. In the phenylethylidenes, Bamford-Stevens insertion into the adjacent methyl group competes with cyclization to an extent which decreases with chain length. At the same time, five-membered ring formation is greatly increased over six-membered ring formation, due to facilitation of out-of-plane twisting of the carbene atom. The mechanistic implications of the results are discussed in terms of an angular approach of the carbene p-orbital to the hydrogen atom under attack. 
ER  -

