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CHEM20018 Reactions and Synthesis

Tutorial 3.

1. Devise syntheses of the following compounds from diethyl malonate with other accessible reagents:

2. Compound A (C9H14O4) was hydrolysed with dilute NaOH. After acidification of the reaction mixture compound B (C7H10O4) was obtained. When B was heated to 100° C a gas was evolved and cyclopentanecarboxylic acid was produced. Suggest structures for A and B and devise a synthesis of A from dimethyl malonate.

3. Devise syntheses of the following compounds from ethyl acetoacetate with other accessible reagents:

4. Give a carbonyl species or pair of species that would generate each of the following on appropriate treatment with base:

5. Trihexyphenidyl is an antispasmodic drug used to treat Parkinson’s disease. It can be made in two steps. Step 1 uses acetophenone and piperidine in a Mannich reaction to give ketone A, and step 2 involves the addition of cyclohexyl magnesium bromide to the ketone A to give trihexyphenidyl. a) What is the structure of A?

b) Provide a detailed mechanism for both steps.

Additional questions

AQ1. Devise a synthesis of the following molecules from diethyl malonate or ethyl acetoacetate.

AQ2. The Robinson annellation is a reaction that uses sequential Michael and aldol reactions to annulate a ring onto a substrate. It can be used to build the AB ring system of steroids. An example of the overall approach is shown below:

a) Provide a mechanism for the Michael addition of the example above.

b) Provide a mechanism for the intramolecular aldol condensation of the example above.

AQ3. The Betti reaction was discovered by Mario Betti (1852-1942). Betti combined 2-naphthol, benzaldehyde and ammonia to obtain the Betti base shown below. Provide a mechanism for this transformation.