2,4,6-trimethyl-1,3-dioxane

Harwood and co-workers (105) utihzed a phenyloxazine-3-one as a chiral derived template for cycloaddition (Scheme 4.50). An oxazinone template can be formed from phenylglycinol as the template precursor. The diazoamide needed for cycloaddition was generated by addition of diazomalonyl chloride, trimethyl-dioxane-4-one, or succinimidyl diazoacetate, providing the ester, acetyl, or hydrogen R group of the diazoamide 198. After addition of rhodium acetate, A-methylmaleimide was used as the dipolarophile to provide a product that predominantly adds from the less hindered a-face of the template in an endo fashion. The cycloaddition also provided some of the adduct that approaches from the p-face as well. p-Face addition also occurred with complete exo-selectivity. Mono- and disubstituted acetylenic compounds were added as well, providing similar cycloadducts. 

The addition product, C QHgNa, called naphthalenesodium or sodium naphthalene complex, may be regarded as a resonance hybrid. The ether is more than just a solvent that promotes the reaction. StabiUty of the complex depends on the presence of the ether, and sodium can be Hberated by evaporating the ether or by dilution using an indifferent solvent, such as ethyl ether. A number of ether-type solvents are effective in complex preparation, such as methyl ethyl ether, ethylene glycol dimethyl ether, dioxane, and THF. Trimethyl amine also promotes complex formation. This reaction proceeds with all alkah metals. Other aromatic compounds, eg, diphenyl, anthracene, and phenanthrene, also form sodium complexes (16,20). 

Sulfonation of the aromatic ring of l, 2, 2 -trifluorostyrene below 0 C does not give satisfactory yields with chlorosulfonic acid or a sulfur trioxide-dioxane complex Tar forms on heating In contrast, under similar conditions ipso substitution IS facile at the position of a trialkylsilyl or -stannyl group Thus, 4-trimethyl-silyl-T 2, 2 D-trifluorostyrene affords the corresponding trimethylsilyl sulfonate [20] (equation 9)... 

In contrast, the same substrate (291) gave trimethyl 8-chloro-4-piperidinopyr-rolo[l,2-fl]quinoxaline-l,2-3-tricarboxylate (293) [Me02CC=CC02Me (2 mol), dioxane, reflux, 6 h 30%]" ° " or dimethyl 8-chloro-4-piperidino-pyrrolo[l,2-fl]quinoxaline-l,3-dicarboxylate (294) [HC=CC02Me (2 mol), dioxane, reflux, 10 h 16%] ° mechanisms are suggested." °... 

Ci,H 7N04S2 138890-87-6) see Brinzolamide 3,7,ll-trimethyl-2,6,10-dodecatrienol (C]5H260 4602-84-0) see Indometacin farnesil 2,2,8-trimethyl-S-formyl-4H-pyrido[3,4-d]-l,3-dioxane (C, H 3N03 6560-65-2) see Cicletanine... 

B. l,3>2>Dioxaphospholens.—The kinetics of the addition of trialkyl phosphites to benzil have been investigated spectrophotometrically. The second-order reaction of trimethyl phosphite in dioxan has activation parameters of A// = 8.4 kcal mol and AS = — 47.5 e.u. In benzene the rate constant increases linearly with low concentrations of added organic acid and decreases linearly with low concentrations of added base. The Diels-Alder mechanism is considered unlikely on the basis of these data, and the slow step is considered to be nucleophilic addition of the phosphite to the carbon of the carbonyl group (see Scheme). 

Trimethyl-l,3-dioxane (146) is the major product formed when the palladium complex of 3-methy 1-1 -butene is treated with formaldehyde. The dioxane products (146, 147) can also be obtained directly in improved yield from the olefin using the catalytic system PdCl2-CuCI2 (Scheme 169).240... 

Dimethylformamide (DMF), dioxane, piperidine, methylene chloride, acetonitrile, trimethyl orthoformate (TMOF), sodium borohydride, diisopropylcarbodiimide, and trifluoroacetic acid (TFA) were purchased from Aldrich Chemical Company, Inc. and used without further purification. All of the diversity reagents were purchased from Aldrich except for Fmoc-glycine-OH, which was purchased from Novabiochem. 

C-alkylated Meldrum s acid derivatives are cleaved asymmetrically by alkoxide anions in the presence of quininium salts to yield chiral half esters (9.2.2) [11]. Thus, benzylquininium and cinchonidinium salts produce fl-hemi-esters and the cincho-nium and quinidinium salts produce the S-hemi-esters from, for example, 2,2,5-trimethyl-5-pheny 1-1,3-dioxane-4,6-dione. 

Olsen and co-workers used a solution of nitronium tetrafluoroborate in acetonitrile for the V-nitration of acetamides and urethanes at —30°C. The following nitramides were obtained by this method V-nitroacetamide (13 %), V-nitro-2-chloroacetamide (55 %), V-nitro-n-butylacetamide (40 %), V-nitrobenzamide (53 %), ethyl V-nitro-n-butylcarbamate (91 %) and V-nitrosuccinimide (43 %). The low yield of V-nitroacetamide, a primary nitramide, is attributed to competing hydrolysis due to the release of tetrafluoroboric acid as the reaction progresses. The scope of the reaction is improved by moving to more basic solvents like ethyl acetate, 1,4-dioxane and trimethyl phosphate. ... 

LiChrosphr lOODIOL UV254 nm 2,2,4-trimethyl pentane/1,4 dioxane (50/50) Benzoic and gallic acids Dodecyl-, Propyl-, Ethyl-,Methylgallate 37... 

A famous use of electrochemical reduction of porphyrin systems is that used to convert a chlorophyll a derivative, chlorin-e6 trimethyl ester (64), into a chlorophyll b derivative, rhodin-g7 trimethyl ester (65) (71LA(749)109). Electrolysis of chlorin-e6 trimethyl ester gave the chlorin-phlorin which was photolyzed in dioxane/water to give the trans-d o (Scheme 7) this was simply transformed into rhodin-g7 trimethyl ester (65) to accomplish the first ever interconversion of a chlorophyll a series pigment into one of the companion b series. 

An interest in anomalous CD properties of 4,4-dimethyl-3-keto steroids and 4,4,8/3-trimethyl-3-keto steroids117118 continued in the studies of Tsuda and coworkers on onoceranediones119,120. Analysis of the CD spectra of 31-35 in methanol and dioxane led to the conclusion that the A-ring conformation in solution is in equilibrium between chair... 

Scheme 1. Key a) alkaline HOOH, THF b) NaSPh, THF c) m-CPBA, CH2CI2, -78 °C d) 2 LDA, HMPA or DMTP, THF, -35 °C then 2-(2-bromoethyl)-2,5,5-trimethyl-1,3-dioxane e) AI(Hg) amalgam, wet THF f) p-CH3PhS02NHNH2, neat, 1 mm Hg g) 4 BuLi, TMEDA, 0 °C then DMF h) DIBAH, Et20, -78 °C then TMSCI, pyridine, CH2CI2 i) t-BuLi, THF, -30 °C then HOAc, -78 °C j) propionic anhydride, DMAP, pyridine, CH2CI2.

Trimethyl-l,3-dioxane-2-yl)thiophene 2-Bromoethyl methylether 2-(Bromomethyl)ethyl methyl ether Propylamine... 

C and THF (20 mL) was added. Sulfur dioxide was then passed through the surface of the mixture for 30 min. The mixture was warmed to ambient temperature and stirred for an additional 15 min. The volatiles were evaporated and to the residue was added water (50 mL) and sodium acetate trihydrate (9.55 g, 70.2 mmol). The solution was cooled on an ice bath and hydroxylamine-O-sulfonic acid (4.62 g, 40.9 mmol) was added. The mixture was stirred at ambient temperature for 1 h, extracted with ethyl acetate (3x100 mL) and the combined extracts were washed with a sodium bicarbonate solution, brine and dried over molecular sieves. Evaporation to dryness gave a viscous liquid (4.93 g), which was chromatographed (silica, eluting with 33% ethyl acetate-hexane) to give a solid 3-(2,5,5-trimethyl-l,3-dioxane-2-yl)-2-thiophenesulfonamide (2.47 g, 72%) m.p. 200°-202°C. 

Fiihrt man die Hydrolyse 41> einer verdiinnten Losung von Borsaure-trimethyl- oder Borsaure-tri-n-propylester in Ather, Athanol, Dioxan oder Testbenzin in Gegenwart von Ammoniak mit einem organischen Losungsmittel durch, das 1 bis 10% Wasser enthalt, so erhalt man nach dem Trocknen die Polyborate... 

The X-ray structures of two anthraquinone derivates of 1,3-dioxane were published. In both 1 -methoxy-4-(2-methylprop-2-enyloxy)-2-[(2i ,6i )-4,4,6-trimethyl-1,3-dioxan-2-yl]-anthraquinone and 4-hydroxy-3-(2-methyl prop-2-enyloxy)-2-[(27 ,67 )-4,4,6-trimethyl-l,3-dioxan-2-yl]anthraquinone the 1,3-dioxane ring adopts the chair conformation and the substituents in positions 2 and 6 are in equatorial conformations (99AX(C)436). Finally, Freeman et al. (02JMS(T)43), employing both ab initio theory and density function theory, calculated the energies of chair, half-chair, sofa, twist, and boat conformers of 1,3-dioxane. 

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