Chitranjan

MEERWEIN-PONNDORF-VERLEY REDUCTION: REDUCTION OF ALDEHYDES AND KETONES TO ALCOHOLS

August 5, 2023 / By

The reduction of aldehydes and ketones to the primary and secondary alcohols represents important synthetic transformations. One of the most chemoselective and mild reactions for these types of reductions is the Meerwein-Ponndorf-Verley (MPV) reductions. It is the reduction of aldehydes and ketones to the corresponding alcohols using aluminum alkoxide (usually aluminum isopropoxide) in the presence …

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DIELS-ALDER REACTION: [4 + 2] CYCLOADDITION

July 31, 2023 / By

The Diels-Alder reaction is a chemical process between a conjugated diene and an alkene, also known as a dienophile. This reaction results in the formation of unsaturated six-membered rings (cyclohexene). Due to the creation of a cyclic product via a cyclic transition state, it is often referred to as a “cycloaddition” reaction. This pericyclic reaction …

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COPE REARRANGEMENT

July 30, 2023 / By

The thermal [3,3]-sigmatropic rearrangement of 1,5-dienes to the regioisomeric 1,5-dienes is called the Cope Rearrangement. The main product is the thermodynamically more stable regioisomer. The reaction is reversible, and the reaction is shifted toward the forward direction (on the product side) if the product is more stable due to stabilization by conjugation or the double …

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WITTIG REACTION

July 30, 2023 / By

The Wittig reaction is perhaps the most commonly used method for the synthesis of alkenes. The reaction occurs between a carbonyl compound (aldehyde or ketone) and a phosphorus ylide to give an alkene with phosphorus oxide as the by-product. In other words, the formation of carbon-carbon double bond (olefins/alkenes) from carbonyl compounds (aldehyde/ketone) and phosphorus …

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CLAISEN REARRANGEMENT: [3,3]-SIGMATROPIC REARRANGEMENT

July 16, 2023 / By

Thermal [3,3]-sigmatropic rearrangement of allyl vinyl ether (or allyl phenyl ether) to the corresponding unsaturated carbonyl compounds are called the Claisen rearrangement. It was first reported by Ludwig Claisen in 1972. There are different variations of Claisen rearrangement like Bellus-Claisen rearrangement, Eschenmoser-Claisen rearrangement, Ireland-Claisen rearrangement, Johnson-Claisen rearrangement, Kazmaier-Claisen rearrangement, Aza-Claisen rearrangement, etc. MECHANISM: Mechanistically the …

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BIRCH REDUCTION

July 16, 2023 / By

The 1,4-reduction of aromatic rings to the corresponding unconjugated cyclohexadiene by alkali metals (Li, Na, K) dissolved in liquid ammonia in the presence of an alcohol is called the Birch reduction. Although the relative rates of reduction with the alkali metals and ethanol in liquid ammonia follow the order Li > Na > K, all …

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BECKMANN REARRANGEMENT

July 10, 2023 / By

The rearrangement of ketoximes to the corresponding amide is known as the Beckmann rearrangement. It accomplishes in one stroke both the cleavage of a carbon-carbon bond and the formation of a carbon-nitrogen bond. This is achieved through the conversion of the oxime’s -OH group to a good leaving group (e.g., H2O, OTs, OMs, Cl, etc.) …

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WAGNER-MEERWEIN REARRANGEMENT

July 10, 2023 / By

The generation of a carbocation followed by the [1,2]-shift of an adjacent carbon-carbon bond to generate a new carbocation is known as the Wagner–Meerwein rearrangement. It is named after the German chemist Hans Meerwein and Fritz Wagner, who independently discovered and studied the rearrangement in the early 20th century. The Wagner-Meerwein rearrangement is closely related …

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PINACOL – PINACOLONE REARRANGEMENT

July 4, 2023 / By

The Pinacol-pinacolone rearrangement is a notable organic reaction that involves the rearrangement of a pinacol (1,2-diol) to form a pinacolone (ketone/aldehyde) compound. This reaction was first discovered by Wilhelm Rudolph Fittig in 1860. This rearrangement involves a 1,2-shift of substituents with concomitant formation of a C-H or C-C bond α to a carbonyl group. The …

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CURTIUS REARRANGEMENT: UNRAVELING MOLECULES THROUGH REARRANGEMENT MAGIC

July 4, 2023 / By

The thermal decomposition of acyl azides to the corresponding isocyanates is known as the Curtius rearrangement. This rearrangement is named after the German chemist Theodor Curtius, who first observed this transformation in his studies on azides in 1885. The acyl azides necessary for this transformation (rearrangement) can be prepared from the reaction of acid chlorides …

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