Name Key 215 HH W12-Final Page 2 I (54 points) (1) (28 points) On page 33 of Volume I, a mechanism for the oxidation of a secondary alcohol using Jones reagent is shown. Although the mechanism appears mostly acceptable, some details need to be modified. Draw in the box below a step-by-step, curved-arrow mechanism for the following Jones oxidation reaction. You may use H-A and A- as a Broensted acid and base, respectively. Please note that the Cr=O oxygen atom will have to be protonated for the addition of the alcohol OH to the Cr of H 2 CrO 4. (2) (26 points) On pages 90-91 of Volume II, a mechanism for the IBX oxidation of a secondary alcohol is given. The mechanism presented therein seems reasonable. However, the pka of IBX is 2.4 and is not able to deprotonate alcohol OH H s. Accordingly, the mechanism will have to be adjusted. Provide in the box below a step-by-step, curved-arrow mechanism for the following oxidation reaction by IBX. You may start protonating I=O oxygen atom. You may use H-A and A- as the catalytic acid and its conjugate base, respectively.
Name Key 215 HH W12-Final Page 3 II (27 points) On page 133 of Volume II, a mechanism for the transformation of a vinyllithium into its methyl ketone derivative is given. However, the mechanism described does not include the structure of the crucial, chelated intermediate. With the use of a simplified vinyllithium A and amide B, draw in the box below the structure of the chelated intermediate C for the reaction and provide a step-by-step, curved-arrow mechanism for the hydrolytic transformation of C to 2-propenyl methyl ketone (D) and CH 3 (CH 3 O)NH 2 +. Please start drawing mechanistic arrows in the box for the structure for C. You may use H-A and A-, respectively, for an acid catalyst and its conjugate base. III (39 points) Following and slightly modifying the mechanism of the Curtius rearrangement reaction shown on page 98 of Volume I, propose in the box below a step-by-step, curved-arrow mechanism for the following reaction. You may use H-A and A-, respectively, for a Broensted acid its conjugate base.
Name Key 215 HH W12-Final Page 4 IV. (27 points) On page 22 of Volume II, a mechanism is described for the conversion of hydroxy epoxide 7 to hydroxy ketone 8. However, this is a two step reaction and HF-pyridine complex is used in the second step to remove the silyl group in the silyl ether ketone E (see the experimental on page 25, Volume II). Provide in the box below a step-by-step, curved-arrow mechanism for the formation of silyl ether ketone E from hydroxy epoxide 7. Please note that 2,6-lutidine is a bulky non-nucleophilic base. V (9 points) Complete the following reaction sequence by drawing in the boxes the appropriate structures (see page 201 of Volume I).
Name Key 215 HH W12-Final Page 5 VI (16 points) On page 77 of Volume II, a mechanism for the (CH 3 ) 2 AlCl-catalyzed Diels-Alder reaction of 20 to form 21 is shown. Its FMO concept-based treatment of the reaction is described on page 85 of Volume II. However, this treatment is for an electrocyclic reaction. In the box below, draw the HOMO or LUMO of the two interacting π-systems using 2p atomic orbital lobes with appropriate signs (shaded or non-shaded) in the abbreviated structure in the box. Designate which is HOMO or LUMO. In addition, answer the questions given in the box. Please ignore the effect of the Lewis acid catalyst. VII (6 points) Draw in the box below a step-by-step, curved-arrow mechanism for the following reaction. Please note the O-O is the weak bond and the Se atom works as a nucleophile. For your information, there are at least three descriptions on this reaction in the final exam course packs.
Name Key 215 HH W12-Final Page 6 VIII (29 points) (1) (20 points) What is the major spiro-bicyclic product G expected from the treatment of hydroxy ester F with NaH? Draw in the box the structure of the product G. In addition, provide in the box below step-by-step, curved-arrow mechanism for the transformation of compound F to the spiro-bicyclic product G. (2) (9 points) Titanoxide intermediate H in the transformation of 13 to 12 (see page 146 of Volume I) is likely to react in a similar manner as shown in (1). Provide in the box below step-by-step, curved-arrow mechanism for the transformation of compound H to lactone 12.
Name Key 215 HH W12-Final Page 7 IX (33 points) Draw in the box below a step-by-step, curved-arrow mechanism for the following new ester formation reaction. A mechanism of a closely related reaction that involves a mixed-acid anhydride intermediate is described on page 154 of Volume I.