3-Vinylcyclohexene oxide synthesis

Fig (25) Catechol (201) on oxidation with silver oxide generates 3-isopropyl-o-benzoquinone (199) which undergoes ultrasound-promoted cycloaddition with 6,6-dimethyl-1 -vinylcyclohexene (200) yielding the synthesis of miltirone (197). 

Dihydroxytanshinone was obtained by the ultrasound-promoted Diels-Alder reaction between a benzofurandione and a vinylcyclohexene, followed by oxidation and desilylation as illustrated in the following scheme <04T1665>. A fully functionalized benzofuran was also utilized as a major building block in the total synthesis of kendomycin <04JA14720>. Benzofuran-based tetraols were also employed as key fragments in the synthesis of some helical molecules <04H(63)137>. 

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