Initials______________ Chemistry 634, Fall 2011 Final Exam Prof. Donald Watson 300 points (3 hours) • • • • • Closed note, closed book. No calculators allowed. You may use a molecular model set. Answers should be written in boxes provided. Other markings will not be considered. Scratch paper can be found at the back of the exam packet. Please initial each page at the top. Points will only be awarded for clearly communicated answers. Please make sure you have all pages of the exam packet (12 pages). Name _______________________________________ Question 1: ________/25 Question 2: ________/23 Question 3: ________/32 Question 4: ________/20 Question 5: ________/40 Question 6: ________/40 Question 7: ________/40 Question 8: ________/40 Question 9: ________/40 _____________________ Total:_______/300 Page 1/12 Initials______________ 1) (25 points, 5 points each) Predict the expected major product for each reaction sequence after aqueous work-up, drawing your answer in box provided. Denote stereochemistry where needed. If no reaction is expected, state so. 1) TsNHNH2 2) NaBD3CN, TsOH O t-Bu O O O Et N 1) LDA, then MeI 2) NaBH4 Bn O Ph Li(sBu)3BH Me Me H O iPrMgBr H V(O)(acac)2, tBuOOH Bu OH _______/25 points Page 2/12 Initials______________ 2) (23 points) In the spaces below, provide the missing reagents and intermediates needed to complete the synthesis. Note: More than one step or reagent may be required over each arrow. TBDPSO 1) O3, then DMS 2) BuLi,1, 0 °C 8 pt O O OBn PPh3 Br Me Ph 7 pt 1 Me Me O Me N O O Me NH2 O O 8 pt O OH Me Me Me O _____/23 points 3) (32 points) In the spaces below, provide the missing reagents and intermediates needed to complete the synthesis. Note: More than one step or reagent may be required over each arrow. Ph O O O 8 pt OH O Me OH O Me Me Me OEt 8 pt OMOM Me Me HO OH O Me Me Me O F3C OH , Et3SiH Me Me OH O Me OMOM 8 pt OMOM 3 2 Cl O OH Cl Cl DMAP, 125 °C Et MOMO O O O 8 pt O O Me Me Et O Me Me OMOM ______/32 points Page 3/12 Initials______________ 4) (20 Points) Referring to the Scheme shown in Question 3, in the space below, please provide a detailed mechanism for the conversion of 2 to 3, and rationalize the observed stereochemistry. ______/20 points Page 4/12 Initials______________ 5) (40 points) In the space below, please provide a detailed mechanism for the reaction shown that accounts both for the connectivity and stereochemistry of the product. 1) Bu2BOTf, iPr2NEt 2) PhCHO O Ph Me O OH Ph Ph Me ______/40 points Page 5/12 Initials______________ 6) (40 Points) A) Please provide a mechanism for the transformation shown below. For now, you can ignore stereochemistry. NP(S)Ph2 Br Br Me2S OEt Br NHP(S)Ph2 O O OH K2CO3 CO2Et 90%, dr = 96:4 20 pts B) Using Newman Projections, in the space below please provide a reasonable model to account for the stereoselectivity in the transformation shown in question 6a. 20 pts ______/40 points Page 6/12 Initials______________ 7) (40 Points) A) Please provide a complete mechanism for the transformation shown below. For now, you can ignore stereochemistry. Ph OH Me O OEt 1) PhCHO, tBuOK, 0 °C, 3h 2) DIBAL, then H3O+ O Me O O H 20 pts B) In the space below please provide a reasonable model to account for the stereoselectivity in the transformation shown in question 7a. 20 pts ______/40 points Page 7/12 Initials______________ 8) (40 points) Using a maximum of 5 steps, propose a synthesis of 5 using the given starting material 4 and any other commercial or readily accessible reagents. O O Ph 4 Ph Me 5 ______/40 points Page 8/12 Initials______________ 9) (40 points) Using a maximum of 5 steps, propose a synthesis of 7 using the given starting material 6 and any other commercial or readily accessible reagents. Me N NH2 I 6 O 7 CO2Me ______/40 points Page 9/12 Initials______________ This page provided for scratch paper. No answers on this paper will be graded. Page 10/12 Initials______________ This page provided for scratch paper. No answers on this paper will be graded. Page 11/12 Initials______________ This page provided for scratch paper. No answers on this paper will be graded. Page 12/12