Dioxolane 2,2-dimethyl-, hydrolysis

LiBF4, wet CH3CN, 96% yield.Unsubstituted 1,3-dioxolanes are hydrolyzed only slowly, but substituted dioxolanes are completely stable.This reagent proved excellent for hydrolysis of the dimethyl ketal in the presence of the acid-sensitive oxazolidine. ... 

The carbonyl group can be deprotected by acid-catalyzed hydrolysis by the general mechanism for acetal hydrolysis (see Part A, Section 7.1). A number of Lewis acids have also been used to remove acetal protective groups. Hydrolysis is promoted by LiBF4 in acetonitrile.249 Bismuth triflate promotes hydrolysis of dimethoxy, diethoxy, and dioxolane acetals.250 The dimethyl and diethyl acetals are cleaved by 0.1-1.0 mol % of catalyst in aqueous THF at room temperature, whereas dioxolanes require reflux. Bismuth nitrate also catalyzes acetal hydrolysis.251... 

Cyclobutyl-cis-4-trans-5-dimethyl- 1,3-dioxolane, by reaction of erythro-3-methane-sulfonyloxy-2-butyl cyclo-butanecarboxylate with sodium borohydride, 51, 12 hydrolysis to cyclobutane-carboxaldehyde, 51, 13 3,5—CYCLOHEXADIENE—1, 2-DI CARBOXYLIC ACID, 50, 50 A1 a-Cyclohexaneacetaldehyde, 53, 104... 

Irreversible Transesterification. A new preparation of chiral glycerol acetonide (2,2-dimethyl-l,3-dioxolane-4-methanol) involving an enantioselective hydrolysis of 2-0-benzylycerol diacetate to the (R)-monoacetate catalyzed by a lipoprotein lipase (47) has recently been developed. In an effort to prepare the (S)-enantiomer, we have used the aforementioned irreversible transesterification reaction using isopropenyl acetate as an acylating reagent, which upon reaction gives acetone as a... 

Since 1,3-dioxolanes are cyclic acetals it follows that they are readily hydrolyzed by acids. The kinetics of this hydrolysis have been extensively reviewed (57MI43000). The acidic hydrolysis of 1,3-oxathiolanes is of theoretical importance in that there are conflicting reports as to whether the C—O or the C—S bond is ruptured first. It is known that protonation of 2,2-dimethyl-l,3-oxathiolane in fluorosulfonic acid leads to the exclusive formation of dication (68) (71BSF541). Based on deuterium labelling studies, however, the present data suggest that the C—O bond is broken first in aqueous systems (72TL2569). 

The formation of acetals from carbonyl compounds requires acid catalysis and (sometimes) the presence of water-coupling reagents (for instance, anhydrous CUSO4). The conversion of aliphatic aldehydes into dimethyl acetals slightly increases the retention parameters of analytes (ARI = 189 17). The cyclic ethylene derivatives (1,3-dioxolanes, ARI = 212 7, this value is valid only for acyclic carbonyl compounds) are more stable to the hydrolysis and used in GC practice... 

Cyclopropylidene-l,3-dioxanes or -1,3-dioxolanes are ketene acetals and examples of bis-donor-substituted methylenecyclopropanes which undergo facile cycloaddition with electron-deficient alkenes 12. Thus, spiro[2.3]pentanone acetals 13 were obtained after reaction in an aromatic solvent either at room temperature or 40 C. Upon subsequent aqueous workup, hydrolytic cleavage of a C-C bond of the cyclobutane ring took place rather than the expected acetal hydrolysis (Table 7). This cycloaddition was found to proceed in a stepwise fashion as reaction of the dimethyl ( )-but-2-enedioate gave a cisj tram mixture of cycloadducts on further heating, this ratio changed. 

Nucleophilic reactions. Chiral epoxides are converted into 2,2-dimethyl-l,3-dioxolanes with inversion of configuration by reaction with acetone. An efficient procedure for imine formation from ketones and amines specifies TiCU as promoter. Hydrolysis (or alcoholysis) of RCONH2 is achieved in the presence of TiCU in acidic media. 

In the few examples studied thus far, - - the relative order of stability to hydrolysis of a 2,2-dimethyl-1,3-dioxolane ring is cis-fused to a furanoid ring > spiro-fused to a pyranoid ring > cts-fused to... 

CHjOCHjCHOHCHjOH Reaction of 2,2-dimethyl-l,3-dioxolane-4-methanol (Na salt) with the chloromethyl polymer, followed by hydrolysis Leznoff and Wong, 1973... 

Other methods for the preparation of 4 have been published, mainly in the patent literature. For example, it has been claimed that 2-naphthalenesulfonyl chloride reacts with 2,2-dimethyl-l,3-dioxolane-4-ethanol, yielding synthetic intermediate sulfonate 27 (Equation 3.10). Sulfonate 27 was then reacted with the mPEG alkoxide to afford a protected mPEG-diol derivative 28, which after hydrolysis under acid conditions, followed by oxidation with NalO, gave mPEG-propionaldehyde 4 in good yield (Equation 3.10) [124]. 

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