8-Oxabicyclo octa-2,6-diene

RhCl(PPh3)3] (23) and [RhCl(CO)(PPh3)2] (71) catalyze the formation of enol silyl ethers and derivatives according to equation (86). Both the (E) and (Z) isomers of the product are obtained.4353 The dinuclear complex [Rh2Cl2(CO)4] (96) catalyzes the reaction of phenylacetylene with carbon monoxide to give 3,6-diphenyl-l-oxabicyclo-[3.3.0]-octa-3,6-diene-2,4-dione (97) (equation 87).435b... 

Me3Si)2S in the presence of Me3SiOTf induces the rearrangement of bis[(Mes)metha-noyl] bicyclo[2.2.1]hept-5-enes to 2-oxabicyclo[3.3.0]octa-3,7-dienes (equation 20)38. 

A concentrated solution of LiCl04 in EtzO is effective in the allylation of silyl enolates with allyl alcohols and acetates.310 The LiClCL-promoted reaction with silyl enolates enables ring opening of 8-oxabicyclo[3.2.1]octa-2,6-dienes to highly functionalized 1,4-cycloheptadienes, which can be further manipulated for use in natural product synthesis (Equation (83)).311... 

The Claiscn rearrangement of allyl vinyl ethers is usually an irreversible reaction due to the energetic benefit of forming aC-O double bond. However, in strained bicyclic systems the retro-Claisen rearrangement (3-oxa-Cope rearrangement) of y,<5-unsaturated aldehydes has been observed32. Sometimes equilibrium mixtures of vinyl ether and carbonyl compound were found. For example, the ratio of the valence tautomers, bicyclo[3.1.0]hex-2-ene-6-cWo-methanal to 2-oxabicyclo[3.2.l]octa-3,6-diene, is approximately 7 333. Nevertheless this reaction was used in the preparation of a key intermediate in a prostacyclin synthesis34. 

Diethyl 8-Oxabicyclo 3.2.1 octa-2,6-diene-2,4-dicarboxylates (9) General Procedure ... 

The shimalactones, isolated from the cultured marine fungus Emericdla vane-color, are neuritogenic natural products which contain a bicyclo[4.2.0]octa-2,4-diene core structure in combination with an oxabicyclo[2.2.1]heptane moiety [105]. The complex structure of the shimalactones represents quite a synthetic challenge, which was overcome in 2008 by Trauner and coworkers [106] in a convergent synthetic approach using a domino Stille reaction/electrocyclization. 

The cycloheptatriene monoepoxide, 8-oxabicyclo[5,l,0]octa-2,4-diene, gave 2,4,6-heptatrienaldehyde as the major primary product on pyrolysis at 2(X) °C. Irradiation of the cycloheptatriene epoxide gave mixtures of 2,4,6-heptatrienealdehyde, cyclo-hepta-3,5-dienone, and 3-oxatricyclo[4,2,0,0 ]oct-7-ene (252). Irradiation of... 

Oxabicyclo[5,l,0]octa-2,4-diene has been prepared by epoxidation of cyclo-heptatriene its reactions include lithium aluminium hydride reduction to cyclohepta-3,5-dienol, hydrogenation to cycloheptanol, boron trifluoride-catalysed rearrangement to cyclohepta-3,5-dienone, and acid hydrolysis to a mixture of all six cyclo-heptadienols. Pyrolysis of the epoxide gave ring-opened products (see Section 12).2- °... 

The rearrangement of 3-methoxy-8-oxabicyclo[3.2.1]octa-3,6-dien-2-ones was catalyzed by triflic acid leading to multisubstituted furans or methoxytropolones (13JOC11707). 

Also obtained via pyrolysis of l,3,7,8-tetramethyl-2-oxabicyclo[4.2.0]octa-3,7-dien-5-one (2,6-dimethyl-4-pyrone-Butyne-2-Adduct) in refluxing o-dichlo-robenzene [3237]. 

Bis[(diphenylphosphinoyl)methyl] sulfide was converted to (diphenyl-phosphinoyl)methyl vinyl sulfides and to divinyl sulfides in Horner-Wittig type reactions with one or two equivalent(s) of oxo-compounds (ketones or aldehydes) (Schemes 60 and 61). The three-component reaction of lithium alkylselenolates/alkylthiolates, the diphenylphosphine oxide derivative of a bis(propargyl)ether and an aldehyde afforded 3-oxabicyclo[4.2.0]octa-1(8),5-dienes (Scheme 62). ... 

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