1.5- dioxaspiro octane

C15H14N2O6 - iy7J-96-iS) see Rosoxacin dimethyl 2,6-dimethoxyterephthalate (Ci2H 40(j 16849-68-6) see Brodimoprim 6,6-dimethyl-5,7-dioxaspiro[2.S]octane-4,8-dione (C]jH)(,04 5617-70-9) see Ketorolac... 

A different cychzation reaction of 460, by treatment with iodine and silver oxide, gave l,6-dioxaspiro[3.4]octanes 469 (Scheme 130). This heterocychc core present in a series of sesquiterpenic lactones has interesting biological activity and is isolated as secondary metabolites from species of the Compositae family . 

In 1999 Uemuraetal. isolatedattenol A (100) and B (101) (Fig. 1.2.5), both marine natural products exhibiting a moderate cytotoxicity against P388 cells [57], from the Chinese Pinna attenuata. Since they are isomeric triols they differ only in the hydroxyl groups involved in the formation of the ketal functionality, so that this results in a l,6-dioxaspiro[4.5]decane and a 6,8-dioxabicyclo[3.2.1]octane unit as the main structural feature of attenol A and B, respectively. 

On hydrogenation over palladium on charcoal, 3-phenyl-5,8-dioxaspiro[3.4]octa-2-en-1-one was reduced to 3-phenyl-5,8-dioxaspiro[3.4]octan-1-one.15... 

Equation 15.2.6 l,5-Dioxaspiro-[2,6] octanes 16 to 4-formyl-tetrahydropyranes 17 (R = H, alkyl, aryl, heteroaryl, alkoxyaryl)... 

It is surprising that silicagel D 11-10 shows better results than zeolites in the gas phase rearrangement reaction. In the case of 1,6 dioxaspiro[2,5]octane, excellent results were obtained in the presence of this silicagel as well as of pentasil zeolites (20). In the present case, the molecular dimensions of the starting material seem to be to bulky, due to the additional methyl groups, and cannot enter the pore volume of the middle sized weakly acid boron pentasil zeolite. 

SYNTHESIS AND [3+2] CYCLOADDITION OF A 2,2-DIALKOXY-l-METHYLENECYCLOPROPANE 6,6-DIMETHYL-l-METHYLENE-4,8-DIOXASPIRO [2.5] OCTANE and cis-5-(5,5-DIMETHYL-l,3-DIOXAN-2-YLIDENE)HEXAHYDRO-l(2H)-PENTALEN-2-ONE... 

D. cis-5-(5,5-Dimethyl-l,3-dioxan-2-ylidene)hexahydro-l(2H)-pentalen-2-one (6). An oven-dried, 50-mL, round-bottomed flask, equipped with a magnetic stirring bar and three-way stopcock, is flushed with nitrogen. A mixture of 6,6-dimethyl-l-methylene-4,8-dioxaspiro[2.5]octane, 5, (8.48 g, 55 mmol) and 2-cyclopenten-1-one (4.52 g, 55 mmol) in 15 mL of acetonitrile is introduced via syringe and the solution is heated at 60°C for 12 hr. The three way stopcock is replaced with a distillation head. Solvent is removed by distillation (ca. 30-120°C/ca. 20-1.4 mm) and the residue is distilled under reduced pressure (142-143°C, 1.4 mm) to afford 6 (10.0 g, 48 mmol, 77%), which crystallizes upon standing at room temperature (Notes 21, 22). 

Figure 5.2.11. Cellulose pyrolysate obtained at 59(P C and separated on a methyl silicone with 5% phenyl silicone type column. 1 acetic anhydride, 2 pentanal, 3 2-hydroxybutanedialdehyde, 4 1,4-dioxadiene, 5 tetrahydro-2-furanmethanol, 6 2-(hydroxymethyl)-furan, 7 3-methyl-2-hexanone, 8 2-methoxy-2,3-dihydrofuran, 9 2(5H)-furanone, 10 1-acetyloxypropan-2-one, 11 hydroxycyclopentenone, 12 5-methylfurfural, 13 2,3-dihydro-5-methylfuran-2-one, 14 1-cyclopentylethanone, 15 2-hydroxy-3-methyl-2-cyclopenten-1-one, 16 3,5-dimethylcyclopentan-1,2-dione, 17 unknown, 18 3-ethyl-2,4(3H,5H)-furandione, 19 6-methyl-1,4-dioxaspiro[2,4]heptan-5-one, 20 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one, 21 1,4 3,6-dianhydro-a-D-glucopyranose, 22 5-(hydroxymethyl)-furfural, 23 4-cyclopenten-1,2,3-triol, 24 5-ethyl-3-hydroxy-4-methyl-tetrahydrofuran-2-one, 25 levoglucosan, 26 1,6-anhydro-p-D-glucofuranose.

In the case of cyclic bromoacetals the thermal reaction gave bromo esters. Thus, 1 -bromo-5,8-dioxaspiro[3.4]octane (3) underwent thermal ring contraction to 2-bromoethyl cyclo-propanecarboxylate (4), quantitatively, on heating neat at 200°C. This rearrangement did not occur from the homologous a-bromocyclopentanone and a-bromocyclohexanone. ... 

In a 5-mL round-bottom flask equipped with a reflux condenser and a magnetic stirring bar was placed l-bromo-5,8-dioxaspiro[3.4]octane (1 g, 5.2 mmol). The flask was immersed in an oil-bath at 200°C for 5 min. After cooling the reaction mixture, its NMR spectrum showed the rearranged pure product yield 1 g (100%). 

Thermolysis of 6,6-dimethyl-5,7-dioxaspiro[2.5]octane-4,8-dione (31) at 500 °C and 0.05 Torr through a packed silica tube readily affords cyclopropylketene (32) when collected at — 196 °C. On warming to room temperature the ketene dimer, dispiro[2.1.2.1]octane-4,8-dione (33), was obtained in 45% yield. 

Lactones have been converted to (hydroxyalkyljcyclopropyl phenyl ketones on reaction with phenylmagnesium bromide and phenyllithium. Reductive dimerization of ethyl cyclo-propanecarboxylate with sodium gave l,2-dicyclopropylethane-l,2-dione in 69% yield when thionyl chloride treatment was carried out prior to hydrolytic workup, and to dicyclopropyl ketone in 74% yield, when workup included sodium bromate treatment. A related reaction occurred during thermolysis of 6,6-dimethyl-5,7-dioxaspiro[2.5]octane-4,8-dione to give dispiro[2.1.2.1. ]octane-4,8-dione. ... 

Sodium benzenethiolate reacted with 6,6-dimethyl-2-vinyl-5,7-dioxaspiro[2.5]octane-4,8-dione (16) to give the 1,5-addition product only. When ethyl trani-6-(l-heptenyl)-2-oxo-bicyclo[3.1.0]heptane-l-carboxylate (18, R = Et) was treated with potassium benzenethiolate it was converted stereospecifically to the corresponding trawj -cyclopentanone derivative 19 (R = Et) with a defined configuration at the a-carbon atom of the side chain. This reaction proved to be useful for the stereoselective synthesis of prostaglandins. ... 

However, 6,6-dimethyl-l-methylene-4,8-dioxaspiro[2.5]octane, an acetal of 2-methylenecyclo-propane, undergoes a thermally induced [3 + 2] cycloaddition with simple ketones to yield acetals of a-methylene-y-lactones. ... 

Rearrangements of oxaspiro compounds such as l,5-dioxaspiro-(2,6) octane and... 

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