Ch. 16 - Metals in Organic Chemistry

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook

Mullins 1st Edition

Ch. 16 - Metals in Organic Chemistry

Problem 31b

Chapter 15, Problem 31b

Predict the product of the following Sonogashira coupling reactions.
(b)

Verified step by step guidance

Identify the reactants involved in the Sonogashira coupling reaction. The reactants are an aryl or vinyl halide and a terminal alkyne. In this case, the vinyl bromide and the terminal alkyne with a furan ring are the reactants.

Recognize the role of the catalysts and reagents. The reaction uses a palladium catalyst (Pd(PPh3)4) and a copper(I) iodide co-catalyst (CuI) in the presence of a base (iPr2NH). These facilitate the coupling of the alkyne to the vinyl halide.

Understand the mechanism of the Sonogashira coupling. The palladium catalyst first undergoes oxidative addition with the vinyl bromide, forming a palladium-vinyl complex.

The terminal alkyne is deprotonated by the base, forming a copper-acetylide intermediate. This intermediate then undergoes transmetallation with the palladium-vinyl complex, transferring the alkyne to the palladium center.

Finally, reductive elimination occurs, coupling the alkyne to the vinyl group and regenerating the palladium catalyst. The product is a conjugated enyne with the furan ring attached to the alkyne.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Sonogashira Coupling

The Sonogashira coupling is a cross-coupling reaction that involves the formation of carbon-carbon bonds between terminal alkynes and aryl or vinyl halides. This reaction typically requires a palladium catalyst and a copper co-catalyst, facilitating the coupling process under mild conditions. Understanding the mechanism and the role of the catalysts is crucial for predicting the products of the reaction.

Reaction Mechanism

The reaction mechanism of the Sonogashira coupling involves several key steps: oxidative addition of the aryl halide to the palladium catalyst, followed by the coordination of the alkyne, and finally, reductive elimination to form the coupled product. A clear grasp of these steps helps in predicting the structure of the final product and understanding how different substituents on the reactants can influence the outcome.

Regioselectivity and Stereochemistry

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others, while stereochemistry involves the spatial arrangement of atoms in the product. In Sonogashira reactions, the nature of the substituents on the aryl halide and alkyne can significantly affect both regioselectivity and stereochemistry, impacting the final product's properties and reactivity.

Recommended video:

1:38

Polymer Stereochemistry Concept 1

Related Practice

Textbook Question

Predict the product of the following Stille coupling reactions.

(b)

1193

views

Textbook Question

Predict the product of the diorganocuprate cross-coupling reactions shown.

(b)

1042

views

Textbook Question

The trimethylsilyl (TMS) group, used as a protecting group for alcohols, can also be used a protecting group for terminal alkynes. Show how TMS-acetylene could be used to link together two aryl halides using the Sonogashira reaction. [Hint: Deprotection of the TMS-acetylene can be done using KF in H₂O.]

1019

views

Textbook Question

Predict the product of the following Stille coupling reactions.

(a)

997

views

Textbook Question

Predict the product of the diorganocuprate cross-coupling reactions shown.

(a)

1008

views