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Cyclic acetals are very much more stable against acid hydrolysis than acyclic acetals. Consequently acyclic acetals are used practically only when a very mild cleavage is required or when two different protected carbonyl groups must be differentiated in their liberation.
For deprotection (regeneration of the alcohol) Aqueous base (pH >9) [6]; Aqueous acid (pH <2), may have to be heated [7]; Anhydrous base such as sodium methoxide in methanol. Very useful when a methyl ester of a carboxylic acid is also present in the molecule, as it will not hydrolyze it like an aqueous base would.
The general structure of a silyl enol ether. In organosilicon chemistry, silyl enol ethers are a class of organic compounds that share the common functional group R 3 Si−O−CR=CR 2, composed of an enolate (R 3 C−O−R) bonded to a silane (SiR 4) through its oxygen end and an ethene group (R 2 C=CR 2) as its carbon end.
These protecting groups “lock” the sugars into a rigid chair conformation. When the sugar forms the necessary oxocarbenium ion, it flattens at the anomeric position. This change in configuration is a high-energy transformation when cyclic protecting groups are present, and leads to the sugar being “disarmed”. [3]
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 ...
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.
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
The Saegusa–Ito oxidation is a chemical reaction used in organic chemistry.It was discovered in 1978 by Takeo Saegusa and Yoshihiko Ito as a method to introduce α-β unsaturation in carbonyl compounds. [1]