8-Oxabicyclo 4.3.0 nonane

Electrochemical fluorination of a-cyclohexenyl-substituted carboxylic (acetic, propanoic, butanoic, and pentanoic) acid esters (methyl, ethyl, and propyl) results in a series of both perfluoro-9-alkyl-7-oxabicyclo[4 3 OJnonanes and per-fluoro-8-alkoxy-9-alkyl-7-oxabicyclo[4.3.0]nonanes [<8S] (equation 19)... 

Hydrogenolysis of cxo-2-phenyl-9-oxabicyclo[3.3, l]nonan-2-ol proceeds exclusively with retention over Raney nickel and with inversion over palladium. No reduction with palladium occurred at all until a drop of perchloric acid was added (36). 

This latter compound, 36, and the isomeric 9-oxabicyclo[4.2.1]nonane, 37, were obtained as the sole products, in ca 13 87 ratio, by reaction of 3 with A-chlorosuccinimide (NCS) in protic solvents (methanol, dioxane-water mixtures)72. It is noteworthy that similar ratios of the two disubstituted bicyclononane derivatives were obtained, independently of the solvent, also by using A-bromosuccinimide (NBS) as electrophile, whereas a strongly solvent-dependent ratio was observed when A-iodosuccinimide (NIS) was used. Since these reactions should proceed through hydroxy- or alkoxyhalogenation of one of the double bonds, followed by transannular attack of the oxygen function on the cationic center which is formed on the other side of the ring by the reaction of another electrophile with the second double bond, the isomer ratio has been rationalized in terms of a different nature of the intermediates. 

Higher yields of disubstituted 9-oxabicyclo[4.2.1]nonane and 9-oxabicyclo[3.3.1]no-nane derivatives from 3 have been obtained using IV-halosuccinimides as reagent72 vide supra). In this case, a solvent dependent isomer ratio has been observed only with iV-iodosuccinimide and the different dependence on the solvent shown by the three iV-halosuccinimides has been explained again in terms of the different nature of the intermediates (vide supra). 

A chiral complex was used in Ru(N0)Cl(salen )/02/UV/CHCl3 for oxidative desymmetrisation of meso-diols to optically active lactols and lactones, e.g. of cis-1,2 -bis(hydroxyhnethyl)-cyclohexane to (1/ , 6S, 7/ 5)-7-hydroxy-8-oxabicyclo[4.3.0] nonane, cf mech. Ch. 1 [363],... 

One of the earliest reports of C-C bond formation by intramolecular C —H insertion was, in fact, the observation32 that on exposure to lithium diethylamide, ra-9-oxabicyclo[6.1.0]nonane... 

Nearly all examples of epoxidation of alkylidenecyclobutanes involve 3-chloroperoxybenzoic acid.15 58-70 This is because the conditions are mild, the workup is easy and few byproducts are formed. Generally, dichloromethane or chloroform is used as solvent. Solid sodium hydrogen carbonate is occasionally added to avoid acid-catalyzed rearrangement of the spiro compound. For example, 6-isopropylidene-l,4,4-trimethylbicyclo[3.2.0]heptan-3-one reacted with 3-chloroperoxybenzoic acid and sodium hydrogen carbonate to give 2,2,3, 3, 6-pentamethyl-spiro[3-oxabicyclo[4.2.0]octane-8,2 -oxirane]-4-one (4) in quantitative yield. However, without the use of sodium hydrogen carbonate, substantial amounts of 2,2,6,9,9-pentamethyl-3-oxa-bicyclo[4.3.0]nonane-4,8-dione (5) and 2,2,6,8,8-pentamethyl-3-oxabicyclo[4.3.0]nonane-4,9-dione (6) were also formed.15-64... 

Halofluorinations can also be carried out with transannular oxygen participation in the case of unsaturated bicyclic epoxides. Thus, 9-oxabicyclo[6.1,0]non-4-ene (7) is attacked stereo-specifically by A -halosuccinimide and triethylamine tris(hydrogen fluoride) (or 70% HF/py-ridine), to give endo,e fo-2-fluoro-6-halo-9-oxabicyclo[3.3.1]nonane 8 (main product) and eHr/o,eWo-2-fluoro-5-halo-9-oxabicyclo[4.2.1]nonane 9.194... 

G. Conversion of a 6,7-Dideoxyhept-6-enose Derivative to a 7-Aza-8-oxabicyclo[4.3.0]nonane Derivative [35]... 

Orthanolic acid, al 18 7-Oxabicyclo [2.2.1] heptane, e6 7-Oxabicyclo[4.1.0]heptane, e5 6-Oxabicyclo [3.1.0] hexane, e9 2-Oxabicyclo [6.1.0] nonane, e7a Oxacyclobutane, t345 Oxacyclopentane, t66 Oxalylurea, i6... 

We have observed that diol 3, cis-2-butene-l,4-diol, and cis-1,2-bis(hydroxymethyl)cyclohexane react smoothly with TPP-CClq to afford 4 (78%), 2,5-dihydrofuran (65%), and cis-8-oxabicyclo[4.3.0]-nonane 84%). Reaction of diol 5 with TPP-CCli in CH3 CN gives 52% of 5-chloropentanol, 6 (11%), and 1,5-dichloropentane (25%) while diol 7 affords 6-chlorohexanol (48%) and 1,6-dichlorohexane (39%). Comparisons of the ether chlorohydrin dichloride product distributions arising from these simple diols reveal a trend for efficiency of chain closure to 3 - 7 membered rings where the formation of cyclic ethers appear to decrease in order of the following ring size 3-5>6>4-7. 

Treatment of 9-oxabicyclo[3.3.1]nonan-l-ols 1014 with a combination of lead tetraacetate and copper diacetate affords 3-allenyl tetrahydropyran-2-ones 1015 via an alkoxy radical accelerated ((-fragmentation pathway (Equation 396) <2001TL2047>. 

Fig. 11 Synthesis of (+)-(lfi,6S)-cw-8-oxabicyclo[4.3.0]nonan-7-one from cw-l,2-bis(hydroxy-methyl)cyclohexane catalyzed by HLADH. The cofactor NAD+ is regenerated by the system pyruvate/L-LDH...

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