Search results
Results from the WOW.Com Content Network
Ethylene glycol protects a ketone (as an acetal) during an ester reduction, vs. unprotected reduction to a diol. A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction.
The degree of conversion to acetal is determined by the equilibrium constant of the reaction: GG-Reaktion zu Acetalen. The most common technique to complete the acetal formation is to remove the reaction water by azeotropic distillation with organic solvents that are not miscible with water, such as benzene or toluene. The tendency of propenal ...
Generic structure of acetals. In organic chemistry, an acetal is a functional group with the connectivity R 2 C(OR') 2. Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments not hydrogen. The two R' groups can be equivalent to each ...
Carbonate ester (cyclic) carbonyl diimidazole, sodium hydride, dimethylformamide: phenyllithium: Diol 33 was protected as a cyclic carbonate ester (Scheme 4). Treatment of the carbonate ester with phenyllithium deprotected one hydroxyl group and left a benzoyl group needed for Taxol on the other oxygen (alcohol 44, Scheme 5). Dimethyl acetal
In organic chemistry, an acetonide is the functional group composed of the cyclic ketal of a diol with acetone. The more systematic name for this structure is an isopropylidene ketal. Acetonide is a common protecting group for 1,2- and 1,3-diols. [1] The protecting group can be removed by hydrolysis of the ketal using dilute aqueous acid.
Trimethyl orthoformate is a useful building block for creating methoxymethylene groups and heterocyclic ring systems. It introduces a formyl group to a nucleophilic substrate, e.g. RNH 2 to form R-NH-CHO, which can undergo further reactions.
The example below depicts the acetalisation reaction of D-ribose 1. With acetone or 2,2-dimethoxypropane as the acetalisation reagent the reaction is under thermodynamic reaction control and results in the pentose 2. The latter reagent in itself is an acetal and therefore the reaction is actually a cross-acetalisation.
The reaction as originally reported involved formation of a silyl enol ether followed by treatment with palladium(II) acetate and benzoquinone to yield the corresponding enone. The original publication noted its utility for regeneration of unsaturation following 1,4-addition with nucleophiles such as organocuprates. Saegusa-Ito oxidation