How alkenes are synthesized from alcohols?

One way to synthesize alkenes is by dehydration of alcohols. Alcohols undergo E1 or E2 mechanisms to lose water and form a double bond. This mechanism is analogous to the alkyl halide mechanism. The only difference is that hydroxide is a very poor leaving group so an extra step is required.

Which of the following reagent is used for the formation of trans diols from olefins?

Osmium tetroxide (OsO4) is a volatile liquid that is most useful for the synthesis of 1,2 diols from alkenes. (Side note: another name for 1,2 diols is vicinal diols, or vic-diols). The reaction is very mild, and usefully leads to the formation of syn diols.

How are diols formed?

1,3-Diols can be prepared by hydration of α,β-unsaturated ketones and aldehydes. The resulting keto-alcohol is hydrogenated. Another route involves the hydroformylation of epoxides followed by hydrogenation of the aldehyde. This method has been used for 1,3-propanediol from ethylene oxide.

How are alcohols used to synthesize alkenes?

One way to synthesize alkenes is by dehydration of alcohols, a process in which alcohols undergo E1 or E2 mechanisms to lose water and form a double bond. The dehydration reaction of alcohols to generate alkene proceeds by heating the alcohols in the presence of a strong acid, such as sulfuric or phosphoric acid, at high temperatures.

How does dihydroxylation of alkenes lead to diol?

Cyclopropyl malonoyl peroxide, which can be prepared in a single step from the commercially available diacid, enables an effective dihydroxylation of alkenes in the presence of water at 40°C. Alkaline hydrolysis of the resulting monoester leads to the corresponding diol. With 1,2-disubstituted alkenes, the reaction proceeds with syn selectivity.

Why is the asymmetric dihydroxylation of alkenes important?

Asymmetric dihydroxylation of alkenes is one of the cornerstone reactions in organic synthesis, as it provides a direct entry to optically active vicinal diols, which are a subunit in a large number of naturally occurring compounds and also important building blocks in many syntheses.

How is the aerobic acetoxyhydroxylation of alkenes catalyzed?

An aerobic acetoxyhydroxylation of alkenes is cooperatively catalyzed by organic nitrite and palladium at room temperature using clean and cheap air as the sole oxidant. Various vicinal diols, diacetoxyalkanes, and dihalogenoalkanes have been synthesized. X.-M. Chen, X.-S. Ning, Y.-B. Kang, Org. Lett., 2016, 18, 5368-5371.