78336-45-5Relevant academic research and scientific papers
Reactions of phthalans with dienophiles. III. Formation of homoquinones by reaction of 1,1-diethoxyphthalans with quinones
Contreras, Luis,MacLean, David B.,Faggiani, Romolo,Lock, Colin J. L.
, p. 1247 - 1256 (2007/10/02)
Treatment of 1,1-diethoxyphthalan with 1,4-benzoquinone gave the homoquinone, ethyl 2-*,6'S*,7'S*)-2',5'-dioxo-3'-norcaren-7'-yl>benzoate, 3, instead of an anthracene derivative expected of a normal cycloaddition reaction.The structure of the homoquinone was deduced from an examination of its spectroscopic properties (ir, 1H nmr, and 13C nmr) and verified by an X-ray crystallographic study.The homoquinone, 3, is triclinic, P1, with a=10.601(2), b=10.434(3), c=6.491(3) Angstroem, α=105.53(3), β=95.21(2), γ=100.66(2) deg and has two formula units per unit cell.The crystal structure was determined by direct methods and refined to R1=0.059, R2=0.048, based on 2378 independent reflections.The data set was obtained using a Syntex P21 diffractometer and MoKα radiation.Bond angles and distances within the molecule are normal.Homoquinines were also isolated as major products of reaction of 1,1-diethoxyphthalan and 5,6-dimethoxy-1,1-diethoxyphthalan with 1,4-benzoquinone and 1,4-naphthoquinone.A mechanism for the formation of homoquinones is offered that involves the same type of transient intermediates proposed for the reactions of 1,1-diethoxyphthalans with activated acetylenes and ethylenes.
