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Problem 25b
Predict the product of the following Stille coupling reactions.
(b)
Problem 31a
Predict the product of the following Sonogashira coupling reactions.
(a)
Problem 31b
Predict the product of the following Sonogashira coupling reactions.
(b)
Problem 32
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.]
Problem 33a
Predict the product of the diorganocuprate cross-coupling reactions shown.
(a)
Problem 33b
Predict the product of the diorganocuprate cross-coupling reactions shown.
(b)
Problem 33c
Predict the product of the diorganocuprate cross-coupling reactions shown.
(c)
Problem 34
Based on the stereochemical result alone, how can you tell that this reaction does not proceed by an Sₙ2 mechanism?
Problem 35
Suggest a synthesis of the following molecule starting with the reagents shown, using cuprate cross-coupling as the key step.
Problem 36a
Predict the product of the following epoxide opening reactions.
(a)
Problem 36b
Predict the product of the following epoxide opening reactions.
(b)
Problem 37
The situation shown here is an example where a cuprate is the only organometallic that will allow the product alcohol to be obtained. What is the problem with using a Grignard or an organolithium to attempt the same reaction?
Problem 42
Which of the following solvents are reasonable choices for a Grignard reaction? Justify your choices. [Hint: Carbonyls are good electrophiles.]
Problem 43
A chemist failed to generate the diol using the reaction shown here.
(a) Suggest a reason why this reaction did not work as written.
(b) How could the reaction conditions be modified to allow formation of the diol? [It may require more than one step.]
Problem 44a
A chemist failed to generate the alcohol using the reaction shown here.
(a) Suggest a reason why this reaction did not work as written.
Problem 44b
A chemist failed to generate the alcohol using the reaction shown here.
(b) How could the reaction conditions be modified to allow formation of the product?
Problem 58
The following transformation is used as an early step in the synthesis of cilastatin, a drug used to counter antibiotic resistance. Identify a possible reagent for this step.
Problem 59
Nitrogen-containing heterocycles form particularly stable carbenes and are commonly used as ligands in organometallic chemistry. (a) Why is the carbene shown particularly stable? [It may be helpful to draw the molecular orbital picture.]
