Dioxolane

Dioxolanes are a group of organic compounds containing the dioxolane ring. Dioxolanes can be prepared by acetalization of aldehydes and ketalization of ketones with ethylene glycol.^[5]

(+)-cis-Dioxolane is the trivial name for L-(+)-cis-2-methyl-4-trimethylammoniummethyl-1,3-dioxolane iodide which is a muscarinic acetylcholine receptor agonist.

Organic compounds containing carbonyl groups sometimes need protection so that they do not undergo reactions during transformations of other functional groups that may be present. A variety of approaches to protection and deprotection of carbonyls^[6] including as dioxolanes^[7] are known. For example, consider the compound methyl cyclohexanone-4-carboxylate, where lithium aluminium hydride reduction will produce 4-hydroxymethylcyclohexanol. The ester functional group can be reduced without affecting the ketone by protecting the ketone as a ketal. The ketal is produced by acid catalysed reaction with ethylene glycol, the reduction reaction carried out, and the protecting group removed by hydrolysis to produce 4-hydroxymethylcyclohexanone.

NaBArF₄ can also be used for deprotection of acetal or ketal-protected carbonyl compounds.^[6][7] For example, deprotection of 2-phenyl-1,3-dioxolane to benzaldehyde can be achieved in water in five minutes at 30 °C.^[8]

PhCH(OCH₂)₂   +   H₂O   ${\displaystyle {\ce {->[{\ce {NaBAr4}}][{\text{30 °C / 5 min}}]}}}$[{\ce {NaBAr4}}][{\text{30 °C / 5 min}}]}}}"> PhCHO + HOCH₂CH₂OH

Neosporol is a natural product that includes a 1,3-dioxolane moiety, and is an isomer of sporol which has a 1,3-dioxane ring.^[9] The total synthesis of both compounds has been reported, and each includes a step in which a dioxolane system is formed using trifluoroperacetic acid (TFPAA), prepared by the hydrogen peroxide – urea method.^[10][11] This method involves no water, so it gives a completely anhydrous peracid,^[12] necessary in this case as the presence of water would lead to unwanted side reactions.^[10]

CF
₃COOCOCF
₃   +   H
₂O
₂•CO(NH
₂)
₂   →   CF
₃COOOH   +   CF
₃COOH   +   CO(NH
₂)
₂

In the case of neosporol, a Prilezhaev reaction^[13] with trifluoroperacetic acid is used to convert a suitable allyl alcohol precursor to an epoxide, which then undergoes a ring-expansion reaction with a proximate carbonyl functional group to form the dioxolane ring.^[10][11]

A similar approach is used in the total synthesis of sporol, with the dioxolane ring later expanded to a dioxane system.^[9]

• Dioxane