Hydroboration-Oxidation Reaction
Concept Map
Hydroboration-oxidation is a crucial reaction in organic chemistry, transforming alkynes into aldehydes or ketones through a two-step process. It begins with anti-Markovnikov hydroboration, forming an alkenylborane intermediate, followed by oxidation to yield the carbonyl compound. This method is highly regioselective and is widely used in pharmaceuticals, fine chemicals, and research.
Summary
Outline
The Hydroboration-Oxidation Reaction with Alkynes
The hydroboration-oxidation reaction is a pivotal two-step sequence in organic synthesis that converts alkynes to their corresponding aldehydes or ketones. Initially, the alkyne undergoes hydroboration, where a borane (BH3 or a related species) adds across the carbon-carbon triple bond. This addition is anti-Markovnikov, meaning the boron atom bonds to the less substituted carbon, forming an alkenylborane intermediate. Subsequently, oxidation with hydrogen peroxide (H2O2) in the presence of a base transforms the intermediate into the desired carbonyl compound. This reaction is highly regioselective, providing a strategic advantage in synthesizing complex molecules while circumventing the limitations of Markovnikov's rule.Hydroboration-Oxidation in Synthetic Organic Chemistry
The utility of hydroboration-oxidation is exemplified in the synthesis of aldehydes from terminal alkynes, such as the transformation of 1-heptyne to heptanal. The reaction proceeds with the addition of a borane derivative to the alkyne, followed by oxidation with hydrogen peroxide and a base, yielding the aldehyde. These reactions serve as practical examples of the method's precision in constructing specific molecular architectures, which is invaluable in pharmaceutical synthesis and the creation of complex organic molecules.Industrial Applications of Hydroboration-Oxidation
Hydroboration-oxidation has broad applications across various industries. In the pharmaceutical sector, it is employed for the synthesis of drug precursors and active pharmaceutical ingredients. The reaction is also integral to the production of fine chemicals, including flavors, fragrances, and dyes. Beyond these, it is utilized in research laboratories for the development of novel chemical entities and in the synthesis of alcohols from alkynes, demonstrating its versatility and critical role in both applied and fundamental chemical research.Mechanistic Aspects of Hydroboration-Oxidation
The mechanism of hydroboration-oxidation involves a series of concerted and stepwise reactions. During hydroboration, the borane acts as a Lewis acid and adds to the alkyne in a syn-addition manner, forming an alkenylborane intermediate. In the oxidation step, the peroxide anion, generated from hydrogen peroxide and base, attacks the boron atom. This nucleophilic attack initiates a sequence of proton transfers, ultimately leading to the replacement of the boron atom with a hydroxyl group and the formation of the aldehyde or ketone. This mechanism underscores the application of Lewis acid-base theory, syn-addition, and regioselectivity in organic synthesis.Hydroboration-Oxidation Versus Alkyne Reduction Techniques
Hydroboration-oxidation and alkyne reduction are distinct yet complementary methods for modifying alkynes. Hydroboration-oxidation is primarily used to generate aldehydes or ketones, while reduction of alkynes typically affords cis-alkenes. These processes are governed by the choice of reagents and catalysts, which steer the reaction pathway and determine the nature of the final product. The interplay between these methods exemplifies the intricate balance of oxidation and reduction reactions in organic chemistry, highlighting the importance of redox principles in the strategic synthesis of diverse organic compounds.
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Overview of Hydroboration-Oxidation Reaction
Definition of Hydroboration-Oxidation Reaction
The hydroboration-oxidation reaction is a two-step sequence in organic synthesis that converts alkynes to aldehydes or ketones
Mechanism of Hydroboration-Oxidation Reaction
Hydroboration Step
During hydroboration, a borane adds across the carbon-carbon triple bond, forming an alkenylborane intermediate
Oxidation Step
In the oxidation step, the alkenylborane intermediate is transformed into the desired carbonyl compound through a series of proton transfers
Applications of Hydroboration-Oxidation Reaction
The hydroboration-oxidation reaction is widely used in pharmaceutical synthesis, production of fine chemicals, and research laboratories for the creation of complex organic molecules
Hydroboration-Oxidation Reaction in Organic Synthesis
Regioselectivity in Hydroboration-Oxidation Reaction
The hydroboration-oxidation reaction is highly regioselective, providing a strategic advantage in synthesizing complex molecules
Utility of Hydroboration-Oxidation Reaction
The hydroboration-oxidation reaction is exemplified in the synthesis of aldehydes from terminal alkynes, showcasing its precision in constructing specific molecular architectures
Comparison with Alkyne Reduction
Hydroboration-oxidation and alkyne reduction are distinct yet complementary methods for modifying alkynes, with the former producing aldehydes or ketones and the latter yielding cis-alkenes
Role of Hydroboration-Oxidation Reaction in Industries
Pharmaceutical Sector
The hydroboration-oxidation reaction is employed in the synthesis of drug precursors and active pharmaceutical ingredients
Production of Fine Chemicals
The reaction is integral to the production of flavors, fragrances, and dyes
Fundamental Chemical Research
Hydroboration-oxidation is utilized in research laboratories for the development of novel chemical entities and in the synthesis of alcohols from alkynes, demonstrating its versatility and critical role in both applied and fundamental chemical research
Hydroboration-Oxidation Reaction
Learn with Algor Education flashcards
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00
During the first step of the reaction, a borane adds to the alkyne in an ______-______ manner, resulting in an alkenylborane.
anti
Markovnikov
01
Hydroboration-oxidation starting material and product
Starts with terminal alkyne, yields aldehyde; e.g., 1-heptyne to heptanal.
02
Reagents used in hydroboration-oxidation
Borane derivative for addition, hydrogen peroxide and base for oxidation.
