Sharp, PhillipMikusek, JiriHo, JunmingKrenske, ElizabethBanwell, MartinCoote, MichelleWard, JasWillis, Anthony2020-08-302020-08-300022-3263http://hdl.handle.net/1885/209116The mechanism associated with the base-promoted conversion of alkoxy-substituted and ring-fused gem-dihalocyclopropanes such as 40 into annulated furans has been explored. Treatment of compound 40 with potassium tert-butoxide affords a mixture of furans 23/27 and 41, an outcome that suggests the intermediacy of the slowly interconverting carbonyl ylides 42 and 43 that undergo rapid [1,5]-electrocyclizations and subsequent dehydrohalogenation to afford the observed products. This proposal is supported by ab initio MO and DFT calculations that also suggest a vinylcarbene insertion pathway is less likely to be operative.The authors thank the Australian Research Council and the Institute of Advanced Studies at the Australian National University for financial support.application/pdfen-AU© 2018 American Chemical Society2018-10-0310.1021/acs.joc.8b01766