M-Dioxane

In a 2-1. round-bottomed flask, fitted with a reflux condenser and mechanical stirrer, are placed 675 g. (8.3 moles) of 37% formalin, 48 g. of sulfuric acid (sp. gr. 1.84), and 312 g. (3 moles) of styrene. The resulting mixture is gently refluxed and stirred for 7 hours. The mixture is cooled, and 500 ml. of benzene is stirred in. The layers are separated, and the aqueous layer is extracted with 500 ml. of benzene. The benzene solutions are combined and washed with two 750-ml. portions of water. The benzene is removed by distillation, and the residual liquid is fractionated under reduced pressure. At 2 mm. pressure a forerun is collected separately, up to a temperature of 96° (Note 1) then the main fraction is collected at 96-103°/2 mm. The yield of 4-phenyl-m-dioxane amounts to 353-436 g. (71-88%) wf 1.5300-1.5311 df 1.092-1.093 (Note 2). 

Methyl-1,3-dioxane m-Dioxane, 4-methyl- (8) 1,3-Dioxane, 4-methyl- (9) (1120-97-4)... 

Fig. 2. Plots of calculated C(t) (a) of 5x 10-1 M HPTA in pure DCM (circles), (b) in presence of 9x I0"3 M DMSO (triangles) and (c) in presence of 0.1 M dioxane (squares). Parameters of die fits, (solid lines) are shown in Table 1.

Prins reaction (cf 10, 186-187). Dimethylaluminum chloride is an effective catalyst for the ene addition of formaldehyde (as trioxane or paraformaldehyde) to mono- and 1,2-disubstituted alkenes.5 When 1.5-2.0 equiv. of the Lewis acid is used, homoallylic alcohols are obtained, usually in high yield. y-Chloro alcohols, formed by cis-addition of -Cl and -CH2OH to the double bond, are sometimes also observed when only 1 equiv. of the Lewis acid is present. The advantage of this reaction over the Prins reaction (using HC1) is that m-dioxanes are not formed as by-products, because formaldehyde no longer functions as a nucleophile when complexed to the Lewis acid. 

Isoprene can be also produced from isobutylene and formaldehyde and the product is of exceptional purity when made by this method. The /.w-butylcnc is first condensed with formaldehyde to yield the cyclic 4,4-dimethyl-m-dioxane, which produces isoprene. 

Fig. 8. ORTEP drawing of [ rra/u-SrtNfSiMejJjEt/u-M-dioxane)]-], showing the trans arrangement of the amide groups and the repeating square planar unit. The O-Sr-N angles have values of 89.6(3)° and 90.4(3)°. (Redrawn from Ref. 57.)...

Pepper JM, Baylis PET, Adler E (1959) The isolation and properties of lignins obtained by the acidolysis of spruce and aspen woods m dioxane-water medium Can J Chem 37 1241-1248... 

Acetic anhydride adds to acetaldehyde in the presence of dilute acid to form etliylidene diacetate [542-10-9] , boron fluoride also catalyzes the reaction (78). Etliylidene diacetate decomposes to the anhydride and aldehyde at temperatures of 220—268°C and initial pressures of 14.6—21.3 kPa (110—160 mm Hg) (79), or upon heating to 150°C in the presence of a zinc chloride catalyst (80). Acetone (qv) [67-64-1] has been prepared in 90% yield by heating an aqueous solution of acetaldehyde to 410°C in the presence of a catalyst (81). Active methylene groups condense acetaldehyde. The reaction of isobutylene/715-11-7] and aqueous solutions of acetaldehyde in the presence of 1—2% sulfuric acid yields alkyl-m-dioxanes 2,4,4,6-tetramethyl- -dioxane [5182-37-6] is produced in yields up to 90% (82). 

The initial cholesteric structure present, especially m dioxane, is considered to be separated into small fragments upon putting the solution between the cone and the plate of the rheogoniometer, and it appears unthinkable that the continuous cholesteric structure is kept during the rotation of the plate. Rheo-optical studies on the liquid crystalline solution have just started (52), and will supply extra information about the solution structure under shearing stresses. 

SYNS BENZALDEHYDE GLYCERYL ACETAL (FCC) BENZYTJDENE GLYCEROL BETYL PHENYL ACETATE FEMA No. 2209 2-PHENYL-m-DIOXAN-5-OL... 

SuKone 2 dissolved m dioxane (250 mL) was treated with t-BuOK (35 1 g. 0.313 mol) under N2 at 0°C, then heated to reflux for 20 h Dilution with water and chrematography on silica gel (hexane) gave 513gof 3 (40%) as a yellow oil... 

Fusions of two ra-dioxane rings are found in the 1,3 2,4- and 2,4 3,5-diacetals of glycitols, and fusions of a m-dioxane and a pyranose ring in the 4,6-acetals of glycopyranosides. If the constituent rings retain the chair forms, the bicyclic systems with trans junctions will be rigid and completely analogous to [Pg.19]

Tellurohenzaldehyde Adduct 1.4 ml of a solution (1.0 M) of trimethylaluminum (1.4 mmol) in hexane are added to a solution of 424 mg (0.6 mmol) of bis [tributylstannyl] tellurium in 10 m/ toluene under argon. The mixture is stirred at 90 for 15 h. The toluene is carefully removed under reduced pressure. 15 m/dioxane, 246mg (3.0mmol) c -2,3-dimethyl-l,3-butadiene, and 106mg (1.0mmol) benzaldehyde are added in sequence to the residue. The mixture is refluxed for 6 h and then poured into water. The product, 4,5-dimethyl-2-phenyl-3,6-dihydro-2H-tetlurine, was obtained after the usual work-up and flash-chromatography on alumina with hexane/dichloromethane (5 1) as the mobile phase yield 49%. 

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