Name_____________Key_____________ 215 F11-Exam No. 2 Page 2 I. (7 points) (a) Show the structures of the two possible conjugate acids of N,N-dimethylacetamide 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.

(b) The pKa value of the conjugate acid of DBU is considerably higher (~12) than that of a typical imine (around 5-7). Draw the structure of the conjugate acid of DBU in the small box below and explain this difference in pKa values using resonance structures of the conjugate acids of both DBU and an imine.

II. (12 points) For each of the following pairs of compounds, predict which compound is more acidic. Compare the two underlined Hs for each pair and circle the compound that is more acidic for each pair.

Name______________Key____________ 215 F11-Exam No. 2 Page 3

III. (28 points) As directed in the boxes below, provide a step-by-step mechanism using the curved-arrow notation for the following base-catalyzed transformations.

IV. (18 points) Draw in the box below a step-by-step mechanism for the NaOCH2CH3-catayzed formation of sodium enolate 6 from β-keto ester 4 and epoxide 5, using the curved-arrow convention.

Name_________________Key__________ 215 F11-Exam No. 2 Page 4 V. (10 points) Treatment of lactone 7 with KOCH3/HOCH3 results in the formation of ester 8 [J. Org. Chem. 2011, 76, 7096]. Provide in the box below a step-by-step mechanism using the curved-arrow convention for this transformation.

VI. (8 points). There are, in principle, four different intramolecular aldol condensation reaction products that could form from 2,6-undecanedione (9) by its treatment with 2% NaOH/H2O/CH3CH2OH. (1) (4 points) Draw in the boxes below the structures of these four potential aldol condensation products.

(2) (4 points) In the box below indicate as to which of these four compounds is expected to be the major product from the reaction and provide a brief explanation for your choice.

Name________________Key___________ 215 F11-Exam No. 2 Page 5

VII. (18 points) Complete the following reactions by providing in each of the boxes the structure of the starting compound, 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) [Org. Lett. 2011, 12, 4524]

(2) [J. Org. Chem. 2011, 7497]

(3) [J. Org. Chem. 2011, 76, 6909]

Name________________Key___________ 215 F11-Exam No. 2 Page 6 VIII. (19 points) Complete the following reactions by providing in each of the boxes the structure of the 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. Org Chem. 2011, 76, 7497]

(2) [Org. Lett. 2011, 13, 4554]

(3) [Chem. Commun. 2011, 11375]