12.7- Dimethyl-1,1,6-dioxaspiro

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... 

Polybia occidentalis W-VG Alarm (2S,6R,8S)-2,8-Dimethyl-1,7-dioxaspiro-[5.5] undecane 142 [188]... 

Recordings from Staphylininae [115] include 3-methylbutanal, the corresponding alcohol, and its acetate, various ketones such as 4-methyl-3-hexanone, 4-methyl-3-heptanone, 5-methyl-3-hexanone (and the corresponding alcohol), 2-heptanone, 6-methyl-2-heptanone, 6-methyl-5-hepten-2-one as well as methyl-cyclopentene and methylfuran. In addition, the secretions of Ontholestes murinus contain the spiroacetals (2S,6R,8S)-2,8-dimethyl-l,7-dioxaspiro[5,5]-... 

Enantiomers of 2,7-dimethyl-l,6-dioxaspiro[4.5]decane 28 Enantiomers of 2-Ethyl-7-methyl-l,6-dioxaspiro[4.5]decane 29 Enantiomers of 2,8-dimethyl-l,7-dioxaspiro[5.5]undecane 30 5 - Methylh eptan - 2 -ol (Z)-Non-3-en-l-ol 3,7-Dimethyloctan- l-ol Benzaldehyde 2-Phenylethanol Phenylacetonitrile Isobutyl benzoate Isopentyl benzoate Hexadecanoic acid 17-Hydroxyan drost-4-en-3-one (2)-Octadec-9-enoic acid... 

The 5-tosyloximes of 2,2-dimethyl-l,3-dioxane-4,5,6-trione react with various dienes in a hetero-Diels-Alder-type reaction. The products, aza-dioxaspiro[5,5]undecenes, readily decompose with basic T-chlorosuccinimide to afford 2-carboxypyridines <1998JOC7840>. The same substrates gave with amines cyanoformamides in 43-73% yield (Scheme 22) <2000H(52)283>. 

However, treatment of (2/ ,3/ )-8-rer/-butyl-2,3-dimethyl-l,4-dioxaspiro[5.4]decane with trimethyliodosilane and hexamethyldisilazane in dichloromethane, followed by deprotection of the silyl ethers with tetrabutylammonium fluoride gives, in a combined yield of 78%, diastereomeric (S)-l-[(l) ,2/i)-2-hydroxy-l-methyl-propoxy]-4-tm-butyl-l-cyclohexene and () )-methylpropoxyl]-4- CT7-butyl-l-cyclohexene in a ratio of 20 1 (by GC)83a. 

The preparation of alkyl methyl ethers may be readily effected under PTC conditions from the alcohol, dimethyl sulphate and 50 per cent w/w aqueous sodium hydroxide, employing tetrabutylammonium hydrogen sulphate as catalyst.95 The usefulness of this procedure has been extended, and optimum conditions have been described for the alkylation of a range of aliphatic alcohols using, for example, 1-chlorobutane or benzyl chloride.96 The PTC preparative examples described in Expt 5.73 are for the methylation, allylation, but-2-enylation and benzylation of, for example, 2-hydroxymethyl-l,4-dioxaspiro[4.5]decane (Expt 5.63), and have been developed in the editors laboratories. These methods have also been applied to the alkylation of protected monosaccharide derivatives (p. 652). 

A mixture consisting of 200 ml methyl alcohol, 1680 ml 40% aqueous dimethy-lamine solution, dimethyl ami nc HCl (303 g), and 200 g potassium cyanide (200 g) was added to l,4-dioxaspiro[4.5]decan-8-one (200 g), then stirred 65hours. A white suspension that formed was extracted four times with 800 ml diethyl ether, then concentrated, and the residue dissolved in 500 ml CH2C12. The organic phase was isolated, dried using Na2S04, then concentrated, and 265 g product isolated as a white solid. 

Aluminum amalgam in reduction of oximinomalononitrile, 48, 2 Aluminum chloride, 46, 109 in conversion of tetramethy 1-1,3-cyclobutanedione to dimethyl-ketene d-lactone dimer, 48, 72 with lithium aluminum hydride, in reduction of l,4-dioxaspiro[4.5 -decane, 47, 37... 

Mercuriocyclization has also been utilized in order to obtain spiroketals from hemiketals. Thus, treatment of l,10-undecadien-6-one (11) with mercury(II) acetate in water/tetrahydrofuran affords, with total regioselectivity, 2,8-bis[(chloromercurio)mcthyl]-l,7-dioxaspiro[5.5]undccanc as a diastereomeric mixture. The diastereomeric ratio was not reported but depends on the reaction time, owing to the reversibility of oxymercuration-cyclization steps. Reductive removal of mercury by sodium borohydride under phase-transfer conditions gives a good yield of 2,8-dimethyl-l,7-dioxaspiro[5.5]undecane (12) as a diastereomeric mixture101,102. 

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). 

Dimethyl-1 -methylene-4,8-dioxaspiro[2.5]oetane 4,8-Dioxaspiro[2.5]oetane, 6,6-dimethyl-1-methylene (9) (122968-05-2)... 

A wide range of 3,3-disubstituted cyclopropenes, e.g. the dimethyl and diphenyl derivatives, as well as spiro[2.4]hept-l-ene or 6,6-dimethyl-4,8-dioxaspiro[2.5]oct-l-ene, can thus be reacted with a variety of mono- and disubstituted alkynes. Usually, the chemoselectivity of this cy-clocotrimerization reaction is remarkably high. The norcaradiene derivatives initially obtained are in equilibrium with the valence tautomeric cycloheptatrienes. The equilibrium ratio of the valence tautomers is strongly dependent on the position and kind of substituents, especially those in the 7-position of the newly formed norcaradienes and cycloheptatrienes. When one or two phenyl groups are present in this position, only norcaradiene products can be detected by and NMR spectroscopy at room temperature, whereas in the case of methyl substituents, both valence tautomers are formed in almost equal amounts. When cyclic alkynes, such as cyclooctyne, are employed in the reaction, only norcaradienes are formed regardless of the substituents present in the cyclopropene cosubstrate. ... 

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. 

Stirring l,l-dibromo-2-phenylcyclopropane in a dimethyl sulfoxide solution of potassium tert-butoxide and ethylene glycol afforded l-phenyl-4,7-dioxaspiro[2.4]heptane (2) in 73% yield, whereas /er/-butyl 2,2-bis(phenoxy)cyclopropanecarboxylate (3) was obtained in 69% yield from tcrt-butyl 2,2-dichlorocyclopropanecarboxylate under phase-transfer conditions using triethylbenzylammonium chloride as catalyst. A further example is given in ref 659. 

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