4-Phenyl-l,3-dioxolane

The acid-catalyzed hydrolysis of 2-alkoxy-2-phenyl-l,3-dioxolanes has been studied. The initial step is rate-determining under eertain eonditions and is deseribed by the rate law given below, whieh reveals general acid catalysis. 

S,5S,2 S)-2-(l-Benzvloxyaminoalkyl)-4,5-bis methoxymethyl]-2-phenyl-l,3-dioxolanes General Procedure4-9 ... 

Methyl-2-phenyl-l,3-dioxolan — 1-Methoxy-l-phenyl-dthan 76°/0d.Th. 

At about the same time that the work described above was being carried out at Glasgow, Kresge and McClelland and their coworkers in Toronto observed that whereas the rate constants (kH+) for the hydronium-ion catalysed formation of 2-hydroxyethyl benzoate from a series of 2-alkoxy-2-phenyl-l,3-dioxolans [69] varied with the alkoxy group at pH4-7.5, they were independent of the alkoxy-group in 5 x 10 2 M hydrochloric acid. 

Observations Six 5-methylene-2-phenyl-l,3-dioxolan-4-one derivatives were prepared... 

TABLE 1. Copoly merization Scoping Reactions Using the Radical Ring-Opening Polymerization Monomer, 5-Methylene-2-phenyl-l,3-dioxolan-4-one, with Methyl Methacrylate... 

The preparation of the radical ring-opening polymerization monomer, 5-methylene-2-phenyl-l,3-dioxolan-4-one, (I), is illustrated in Eq. (1). 

A procedure for bromination of 2-phenyl-l,3-dioxolanes with N,N-dibromobenzenesulfonamide (C6H5S02NBr2) has been described,184 but it has not yet been applied in the carbohydrate field. The behavior of this reagent is essentially identical to that of N-bromosuccinimide, but some differences were noted, and a suggested mechanism was discussed.184... 

The photoaddition of alkanes onto electron-poor alkynes (e.g., propiolate or acetilendicarboxylate esters) can be accomplished by a radical conjugate addition reaction [7]. Radicals have been generated either via hydrogen abstraction from cycloalkanes or via electron transfer from 2-alkyl-2-phenyl-l,3-dioxolanes. In the first case, the irradiation was pursued on an alkane solution of an aromatic ketone (used as the photomediator) and the alkyne. Under these conditions, methyl propiolate was alkylated upon irradiation in the presence of 4-trifluoromethylacetophenone to form acrylate 48 in 97% yield (E/Z= 1.3 1 Scheme 3.31) [78]. 

Bis[(2-phenyl-1,3-dioxolan-2-yl)methyl] Tellurium2 Under an atmosphere of nitrogen 0.30 g (2.3 mmol) finely pulverized tell urium and 0.22 g (9.6 mmol) sodium are s tirred in 15 ml dry dimethylformamide at 110 for 15 min. To the resulting yellowish-white suspension at 20" are added 1.15 g (4.7 mmol) of 2-bromomethyl-2-phenyl-l,3-dioxolane dissolved in 10 ml dry tetrahydrofuran. After 2.5 h at 20° the reaction mixture is poured into water, and the resulting mixture extracted with dichloromethane. Chromatographic separation [silica gel, dichloromethane/petroleum ether (40 60°) (1 1)] from the starting material gives the product yield 60% m.p. 68° (ethanol). 

In the hydrolysis of 1,3-dioxolane, kH is increased by 3.5 powers of ten with the introduction of the first methyl group at the 2-position, but by 1 power of ten only with the introduction of the second methyl group [161]. Furthermore, introduction of a 2-methyl group causes kH to increase by a factor of 2 in the case of 2-phenyl-l,3-oxathiolane [168], but causes kH to decrease by a factor of 5 in the case of 2-phenyl-l,3-dioxolane [165]. 

S708>, and 2-phenyl-l,3-dioxolanes are cleaved cleanly to diols by the use of catalytic erbium triflate <20050BC4129>. A titanium silicate molecular sieve is effective in catalyzing methanolysis of l,3-dioxolan-2-one to give ethanediol and dimethyl carbonate <1996CC2281>. 

The chemical shifts have been measured for the benzyl protons of a series of 2-phenyl-l,3-dioxanes and 2-phenyl-l,3-dioxolanes. These shifts appear to be characteristic not only of ring size but also of configuration at carbon atom 2. 

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