Synthesis and stereochemistry of hydrogenated 1,1,4,4,7a-pentamethylindenes

Abstract

DPciic; 2 la tne'tnoire de Dr. Lc:o ma riot^ ALAN FRANCIS THOMAS, MICHEL OZAINNE, and RENEE GUNTZ-DUBINI. Can. J. Chem. 58. 1810 (1980). Ease of methylation of hydrogenated 2H-inden-2-ones depends on the presence of a double bond in the cyclohexane ring, and occurs readily with compound 20 but not with 10. Differences of reactivity are also noted in Wittig reactions. Most reactions of the system are highly stereoselective. and the stereochemistry of hydrogenated indenes is discussed. ALAN FRANCIS THOMAS, MICHEL OZAINNE et R E N~F .GUNTZ-DUBINI. Can. J. Chem. 58, 1810 (1980). La facilite avec laquelle les indkne-2H ones-2 hydrogenees sont methylees depend de la presence d'une double liaison dans le cycle a six chainons; ainsi, la methylation du compose 20 est beaucoup plus facile que celle du compose 10. On constate egalement des differences de reactivite lors de la reaction de Wittig. La plupart des reactions de ce systkme sont hautement stCreoselectives. ce qui nous a permis d'ailleurs d'approfondir notre connaissance de la stCrCochimie des indknes hydrogines.

Naturally occurring taiwaniaquinoids: biosynthetic relationships and synthetic approaches

“…Wacker oxidation 55 of 29c followed by condensation provided bicyclic enone 29e in excellent yield. 56 Michael addition of the lithium enolate of 29e to methyl vinyl ketone (MVK) formed the keto-enone 29f with high diastereoselectivity. The later was reacted under Robinson annulation strategy followed by reaction with Nphenyltriflimide afforded enoltriflate 29g (Scheme 22).…”

The Catalytic Enantioselective, Protecting Group-Free Total Synthesis of (+)-Dichroanone

“…Wacker oxidation of keto-olefin 7 was performed in a Parr apparatus to afford complete conversion to diketone 10 in 77% yield . Condensation of 10 using KOH in xylenes with azeotropic water removal provided bicyclic enone 6 in excellent yield. ,

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“…16 Condensation of 10 using KOH in xylenes with azeotropic water removal provided bicyclic enone 6 in excellent yield. 17,18 Elaboration of enone 6 to more advanced intermediates was challenging because of the propensity for most carbon electrophiles to react at oxygen preferentially to C(5a) (Scheme 3). Fortunately, Michael addition of the lithium enolate of 6 to methyl vinyl ketone (MVK) at low temperature formed the desired C-C bond of ketoenone 11 in good yield with high diastereoselectivity.…”

“…Despite extensive efforts to develop other oxidations, these conditions were superior to any others tested and were the most direct for the installation of the second oxygen atom. The crude o-quinone 16 was immediately treated with C 6 F 5 SH, which presumably undergoes 1,4-addition into the unsubstituted position, giving after tautomerization a highly reactive catechol (17). Attempts to isolate this catechol led to complex mixtures, including a second highly unstable o-quinone (18).…”