Chemistry ofO‐Benzoquinones and MaskedO‐Benzoquinones I. Diels‐Alder Reactions ofO‐Benzoquinones with Dimethyl Acetylenedicarboxylate and Phenylacetylene

摘要

AbstractDiels‐Alder reactions of sixo‐benzoquinones with dimethyl acetylenedicarboxylate has been examined. The yields of adducts vary with the natures of theo‐benzoquinones, 3,4‐Di‐n‐propyl‐(1c), 3,6‐di‐n‐propyl (1d). 3. 4‐diallyl‐(1e) and 3, 6‐diallyl‐o‐benzoquinone (1f) are found to give bicyclic a‐diketones exclusively without the formation of 1,4‐dioxine derivatives, the yields ranging from 20 to 70. In the case of 4, 5‐dimethoxy‐o‐benzoquinone, dimethyl 4, 5‐dimethoxyphthalate is produced in 42 yield, presumably derived from the decomposition of the corresponding initially formed α‐diketone. 3, 6‐Di‐n‐propyl‐4, 5‐dimethoxy‐o‐benzoquinone deteriorates without addition to dimethyl acetylenedicarboxylate upon heating. The additions ofo‐benzoquinones1c,1dand1fto phenylacetylene are also studie