(5) a. b. (6) N H CH 3 N H O H O (7) CH 3 O (8) OCH 3 2. explanation:

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1 ame Key 15 W1-Exam o. Page I. (16 points) For each of the following pairs of compounds, predict which compound is more acidic. Compare the two underlined s for each pair and circle the compound that is more acidic for each pair. The more acidic compound for each pair will be (circle one): (1) (5) () (6) C () (7) C () C C C C (8) II. (1 points) (a) (6 points) In tne box provided below, draw the structures of the two potential conjugate acids of -dimethylaminopyridine (1) and explain, in several words, as to which of the two conjugate acids is more stable and would be expected to form preferentially. Use drawings of pertinent resonance form(s) and several words to explain your answer. structures of the conjugate acids A C -dimethylaminopyridine (1) C C C C C explanation: A C C Charge in A delocalized over two 's by resonance. C C (b) (6 points) Recently, a similar pyridine compound has been synthesized. In the box provided below, answer if compound should be more basic than -dimethylaminopyridine (1) or not and then provide a brief explanation in using less than 0 words and pertinent resonance structure(s). The answer could be no here if the ring strain is mentioned in the res structure on the right. explanation: Is more basic than 1? yes or no (curcle one that applies) The conjugate acid of is more stabilized by resonance as the -RR group is coplanar with the pyridine ring.

2 ame Key 15 W1-Exam o. Page III. (8 points) The reaction shown below involves the base-catalyzed reaction of aldehyde and α,βunsaturated ketone and consists of a Michael (or conjugate) addition, to form keto-aldehyde intermediate 6, followed by an intramolecular aldol condensation to α,β-unsaturated ketone 5. Draw in the box a step-bystep mechanism for this base-catalyzed reaction using the curved-arrow convention. You may use :- and to represent a base and its conjugate acid, respectively. C C C C a C C C C 5 C C C C intermedite structure: pts each mech. arrows: pts for each set C C E mech - pts C C C C C C C C keto aldehyde intermediate 6 Carbanion struct instead of enolate struct acceptable. C C C C C C 5 8 IV (1 points) ) Draw in the box below a step-by-step, curved-arrow reaction mechanism for the following transformation [J. rg. Chem. 01, 78, 9]. You may use :- and to represent a base and its conjugate acid, respectively. Δ intermedite structure: pts each mech. arrows: pts for each set These deprotonation & protonation steps could be reversed. Acceptable even though it is a 7-membered TS. 1

3 ame Key 15 W1-Exam o. Page V (16 points) Draw in the boxes below a step-by-step, curved-arrow reaction mechanism for each of the following reactions. You need not rationalize the stereochemical outcome for these transformations. (1) (10 points) S Li LiS enatiomer S Li S S intermedite structure: pts each mech. arrows: pts for each set 10 () (6 points) [rg. iomol. Chem. 01, 11, ] a r ar enatiomer a r intermedite structure: pts mech. arrows: pts for each set r 6

4 ame Key 15 W1-Exam o. Page 5 VI. (15 points) Complete the following reactions by providing in each of the boxes the structure of the expected intermediate, or product. Indicate stereochemistry for the product/intermediate and if more than one stereoisomer is formed, draw one structure and write enantiomer or diastereomer. (1) [rg. Lett. 01, 15, 100] 1. a,. (p 1 ~ ) () [Synthesis 01, 51] 1. LiAl. workup () [rg. Lett. in press] 1. LiAl. aq Cl () [rg. Lett. 01, 15, 160] C C C Mgr tetrahydrofuran (solvent) C r Mg C C C aq Cl no need to show stereochem here chelate intermediate C C C Cl

5 ame Key 15 W1-Exam o. Page 6 VII. (19 points) Complete the following reactions by providing in each of the boxes the structure of the expected intermediate, or product. Indicate stereochemistry for the product/intermediate and if more than one stereoisomer is formed, draw one structure and write enantiomer or diastereomer. (1) [J. Am. Chem. Soc. 01, 1, 1978] C C 1. a [Si(C ) ] *. Cl I C C Cl *Strong and non-nucleophilic base. enantiomer () ac C C C C 19 0 C 19 0 () [J. rg. Chem. 01, 78, 786] C C K C C () [ Chem. Commun. 01, 19] C C 1. LiCu(C C=C ). aq Cl workup C C diastereomers (5) Li 1. r r Li C C. workup enantiomer C C or S Δ C C Lir C C C