SYNTHETIC APPLICATIONS OF INTRA-MOLECULAR INSERTION IN ARYLCARBENES .3. GENERATION AND REARRANGEMENT OF ARYLOXYCARBENES BY INTRA-MOLECULAR ABSTRACTION OF HYDROGEN

O-Alkoxy- and o-alkylthio-phenylcarbenes, generated by low-pressure pyrolysis in the gas phase, show abstraction of 2H across space to generate the corresponding o-tolyl vinyl ethers or sulfides. In the case of o-ethoxyphenylcarbene, deuterium labelling shows that this is a case of vicinal abstraction, not geminal abstraction followed by 1, 2-hydride shift. o-Methoxyphenylcarbene, however, is similarly shown to undergo geminal hydrogen abstraction leading to o-tolyloxycarbene, which undergoes a 1, 2-aryl shift to give o-tolualdehyde. Independent generation of aryloxycarbenes has been achieved by pyrolysis of 5-aryloxy-2, 2-dimethyl-l, 3-dioxan-4, 6-diones. The product carbenes show the expected rearrangement as well as normal insertion reactions. © 1979 Australian Journal of Chemistry, All rights reserved.