215 Exam-00-1 - Chemistry 2 1 5 First Examination February...

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Unformatted text preview: Chemistry 2 1 5 First Examination February 1, 2000 Dr. Edwin Vedejs (Sec 100) Dr. Masato Koreeda (Sec 300) (1.5 hr; 100 points) Please CHECK OFF your 216 Lab section. _101 Lecture ONLY _110 M 1-5 PM _111 M 1-5 PM _130 T 1-5 PM _131 T 1-5 PM _132 T 1-5 PM _133 T 1-5 PM _134 T 1-5 PM _150 W 12-4 PM _151 W 12-4 PM _152 W 12- 4 PM _170 TH 1-5 PM _171 TH 1-5 PM _172 TH 1-5 PM _174 TH 1-5 PM _190 F 1-5 PM _191 F 1-5 PM _301 Lecture ONLY _310 M 1-5 PM Please read each question carefully and answer it completely and clearly. A606 A612 CHEM A606 CHEM A612 CHEM A618 CHEM A624 CHEM A630 CHEM A606 CHEM A612 CHEM A618 CHEM A606 CHEM A612 CHEM A618 CHEM A624 CHEM A606 CHEM A612 CHEM A618 CHEM LARSEN, AMY CLARKE, NAGASH CHEN, BIN CLAY, JULIA SMALL, AARON ZHANG, BO DENSMORE, CRYSTAL LARSEN, AMY TURPOFF, ANTHONY ZHANG, LIMING CHEN, BIN CLAY. JULIA TURPOFF, ANTHONY HANN, CLAYTON ZHANG, BO CLARKE, NAGASH SMALL, AARON _31 1 _31 2 __330 _331 _332 _333 _334 ._350 _35 1 _352 _353 _354 _370 _371 _372 _373 _374 _390 _391 —1—1—1-—1—1 “2222255555 a: F Name Please Print Signature Student ID # 1-5 PM A624 CHEM 1-5 PM A642 CHEM 1-5 PM A636 CHEM 1-5 PM A642 CHEM 1-5 PM A730 CHEM 1.5 PM A736 CHEM 1-5 PM A742 CHEM 12-4 PM A636 CHEM 12-4 PM A642 CHEM 1-5 PM A624 CHEM 1-5 PM A630 CHEM 1-5 PM A742 CHEM 1-5 PM A636 CHEM 1-5 PM A642 CHEM 1-5 PM A730 CHEM 1-5 PM A736 CHEM 1-5 PM A742 CHEM 1-5 PM A618 CHEM 1-5 PM A624 CHEM SCHACH, ANDREW CAO, GANFENG STAY, PATRICK SCHEIDEMAN, MATTHEW POON, STEVE TAN, LI ZHENG, NAN SCHACH, ANDREW CAO, GANFENG KOMAZIN, GLORIA DENSMORE, CRYSTAL HANN, CLAYTON STOY, PATRICK SCHEIDEMAN, MATTHEW POON, STEVE TAN, LI ZHENG, NAN ZHANG, LIMING KOMAZIN, GLORIA Complete Lewis structures are acceptable for answers unless you are given other specific instructions. Precision in drawing is an important skill in the communication of organic chemistry concepts. Double Check any three-dimensional representations to ensure you are implying an unequivocal direction of bonding. Do not forget to include important features such as nonbonding lone electron pairs and formal charges when appropriate. The exam has 10 pages in addition to this cover page. The last 3 pages include tables of pKa values for represen- tative acids, electronegativity values for some elements, and bond dissociation energies for representative bonds, and a list of reagents. Individual point values are given in the comer of each answer space. 1 H 1 .00794 3 4 2 I Be 6.941 9.01218 11 12 3 ’1 $977 24.305 4 5 6 E7 88 89 7 Fr Ra Ac 223) I. 0254 27.0278 PERIODIC CHART OF THE ELEMENTS 90-103 ACTIN- IDES (251) 105 (247) (251) 9 96 100 Bk Cf Fm (257) 5 6 7 6 1o flflflflEfi 10.81 12.011 140067159994 :-=:--« 20.179 13 14 15 16 17 16 mapso~ .961 6.0355 30.9376 32.06 35.453 39.946 1 9 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 n66 fllflflfiflfifieeeeewr 39.0963 40.06 44.9559 47.66 50.9415 51.996 54.9380 55.647 58.9332 56.69 63.546 65.36 69.72 72.59 4.9216 76.96 79.904 63.60 37 36 39 40 41 42 43 44 45 46 47 46 49 50 51 52 53 54 65.4676 67.62 66.9059 91.22 929064 95.94 (98) 101.07 02905510542 :.:r.112.41 114.82 116.69 121.75 127.60 26.9045 131.29 55 56 57 58m 72 73 74 75 76 77 7B 79 60 61 82 63 84 Cs Ba La LANTH- Hf Ta W Re Os Ir Pt Au Hg TI Pb Bi Po «m1 137.33 36.9055NIDES 176.49 160.9479 169.65 186.207 190.2 19222 195.06 196.200.59 204.363 207.2 az-u- (209) 104 106 107 -'= -" 110 111 eflflfllli ( (263) 56 59 so 61 63 64 65 66 67 66 69 7o 71 fifififlflmfiflflflflflflmww 140.12 140.90 144.24 (145) 151.96 56.921583 152.50 64.9 I-167.26 66934217304 174.967 90 91 94 95 96 7 Agggrgge Th Pa E Am Cm 0391*“ 4 .44: "4:6 I:-. (244) (243) (247) 101 (258) 85 86 At Rn (210) (222) Md Lr (260) 2 He 4.00260 103 Name Page 1 I (20 points) A number of reactions discussed in the class have been used in recent syntheses of natural products or biologically active compounds. In each case, supply the structure of the product in the box provided. When stereochemistry is known, please show it in the structural formulas you use. When a racemic mixture forms, show the stereochemistry of one enantiomer and write "and enantiomer" in the box. ( 1) Synthesis of an insect pheromone (Synlett 1999, 1298). / (2) Synthesis of the antitumor agent trilobin (J. Org. Chem. 1999, 64, 2381). l \ ’ CCrO' l+ 1 3 H W ————_—_> C10H21 OH dichloromethane GSI initial /\ MgBr tetrahydrofuran workup with aqueous NH4CI Name Page 2 I (continued) (3) Synthesis of analogs of estrone (J. Med. Chem. 1999, 42, 3188). HgN-OH‘HCI NaOH/HZO/ethanol ——-——> mild acidic workup with 1M HCI + H20 (4) Synthesis of the aggregation pheromone of the western pine beetles. TsOH, A -—-—————> benzene intramolecular ketalization product + H20 Name Page 3 II. (20 points) (1) cis-1,2-Cyclohexanediol forms the ketal product upon treatment with cyclopentanone in the presence of a catalytic amount of p-toluenesulfonic acid (TsOH; pKa -O.6). TsOH + —————> 0 +H20 OH benzene, A O OH O Propose a reaction mechanism for this reaction using the curved arrow convention. .l 1 a key tetrahedral intermediate Name Page 4 II. (continued) (2). (-)-Quinic acid has been used as a versatile chiral starting compound for the synthesis of natural products (see, e.g., J. Org. Chem. 1999, 64, 6443). The reduction of the carboxyl group with LiAlH4 presents a serious problem for use of this compound due to the presence of a number of acidic hydrogen atoms in the molecule. In order to circumvent this problem, (—)—quinic acid is treated with cyclopentanone in the presence of catalytic TsOH, producing a ketal—lactone. The LiAlH4—reduction of this ketal—lactone produces the trio] shown below. Provide in the box below the structure of this ketal- lactone. Hooo, OH TsOH \ + i + HO‘“ OH benzene A OH O 05H 80 C7H1206 ketal Iactone C12H1605 LiALH4 tetrahydrofuran workup with aqueous NH4CI Irv Name Page 5 III (20 points) Discodermolide, a promising experimental anticancer agent, has recently been prepared by synthetic means (Org. Lett. 1999, 1, 1823). The purpose was to access larger quantities of this substance (isolation: 7 mg from 0.5 kg of a rare deep—water sponge). The following reactions were carried out early in the multi-step synthesis. Draw structures in the space provided to show ALL organic products formed after step (2) (prior to workup with water) and step (3) (after brief exposure to dilute acid). You may ignore HAl(C4H9)2 decomposition products. CH30 CH3O m Hag H HZCH3 [CH3 m Hag H chH3 [CH3 0 i ’ N o "’ " N M \OCH3 (1) M \OCHS Ho‘H o ——‘> O "H O + BASE I (le3 o (CH3)3C—-Sli—CH3 CH C-Si—O—S—CF CH ( 3% | n 3 HAI(C4H9)2 (2) 3 CH3 0 di|ute HC| (pH 4) room temperature 1 (3) Given that the pKa of trifluoromethanesulfonic acid (CF3SO3 H) is <<0, draw a curved arrow mechanism for step (1); use “R—O-H” as an abbreviation for the starting alcohol and B: to represent a typical base. Draw the products so that any use of abbreviations is consistent with abbreviations shown for reactants. Name . Page 6 IV (10 pomts) Problem 15.19 describes the reaction of A with B and specifies that two equivalents of B are used, but does not indicate why. The reaction of A with B is quite fast, but it does not go to completion if only one equivalent of B is used. Two equivalents of B is enough to achieve nearly complete conversion of A, and a larger excess of B does not affect the outcome. Draw structures in the boxes to show what happens to A and to B and briefly explain why the second equivalent of B is needed. H30 CH3 FROM A: WHAT B DOES: oi Cl A H3C— NH2 B a V (10 points) Chiral esters can be prepared with high enantiomeric purity using a method reported in Synlett. 1999, 195 (Bolm et al.). The procedure employs quinidine, a chiral nitrogen base of natural origin, abbreviated below as R3*N, and starts with an ACHIRAL substance C8H803. Fill in the structure of CgHgO3 and the product formed in step (1). Hints: The pKa of the conjugate acid of R3*N is ca. 10; the mechanism of step (1) is not established, but may be related to problem 14.40 where (C4H9) 3P was used in a related conversion. (1) (2) H CH3OH COZH .9 _+ (I 1.1 equiv dime 5 CO CH R3*N HCI g 2 3 (quinidine) CsH1204 CsHaoa Name Page 7 VI (20 points) Pheromones can be defined as chemicals that play a role in communications between individual insects. Structure Y is the pheromone of the Japanese peach moth and acts as a sexual attractant for the male. Devise a synthesis of Y that proceeds by way of the intermediate X. You may use any monofunctional reagents of eight or fewer carbons and difunctional reagents of three or fewer carbons. Show reagents needed for each step, the product(s) after each step, and specify solvents if this is important for reagent stability. Select methods that are likely to give the desired substance as the major product at each step. i HO(CH2)3— CE 0— (CH2)5CH3 x l l CH3(CH2)7— ([3H(CH2)2— Cl3= ?— (CH2)SCH3 Y OH H H 12 Page 8 E m w e\H e e: 9 G0 a. \H e H.) . n .. .. "NIH . . .C e T .oHc\ ®\c, "s" . I x .m. _ oIR /H e . e e..\H 6. H m A / .OHN H _ Olc a o 2 o I. a o C o. C H ok a e B G 0. a / 2 n / _ m ICIQ e HIN. / \ /H . “M U .. O. m 3 H 3 C H_.. PR H / C CHC HICIH 8 J G G 3 m m C H H Hx /H A v _ Mo W m / \ H m C m 2 2 5 O a O O O 7 1 5 6 1 p 1 2 2 3 3 H 4 m. w H , ) H . \ H H H H d "on H . x. . x H H H H H t m 0| \ H, \ .ua/ \NIH . \H .0 /C\ _ 1 LL 2 \H ,C\ H H/R H H M C Icl. . ®\C/ "m OHC ..O / \ xH GlClC _ H HIN __ / I x /H I. t A .0.. ..OHN H c: / ./H paw OHC/ x_. /H \C/ CIC H r_TH m e . . "/0" mm m3 3 "m. C H H H / \ H M. G .. m C ‘/ V W E m ) B m G: H 9 G E .w . 2.9 e @: ..\ H "m" ..o.. e: H/..\H 3 e A muonsuo "H..." "O. ..o/ .\ ..omvk 0.1% .G «on w e: . on G H“ .n_v. .. . 2 / .l f . | / "z" .onc H, \c .\o. "\o“ ..onc\ @ N H m. U Wu J”. m H .0” Pay) .- c OHC OHC o o- /C\ J /\ 3 a. G _ o / o / no In \ / H/ \H _ N m / w... "m" .. IC/ H e: w / m H H a 4 7 H H H H H H 3 H H. H H H 5 H D. 1 3 4 An . l 4 H _ H H H H H m d M. w” H H .H .H. H 3 q: _ . x @H .o . .o .l .\o. e. .H. H . \ .H. D e . “JUNO. . I. G HI..0/ H10 ..O“N\ .OHPW .F. .OIC HIWIH .\O. .O OHC/ \H H .0. I. Mo 0. _ _ 2 ../ .. x . . / _ . Hz \C .muHC OHC\ . C N _ H E m H H. H H H H ..H. H. H H _ .. / , ,H H _ t 3 . 3 O . / Kw m G / w H m. H H / Page 9 Table 1.2 Electronegativity Values for Some Elements 1 2 13 14 15 16 17 Table 2.4 Average Bond Energies [kJ/mol (above) and kcaI/mol (be/own Single Bonds 565 431 364 297 135 103 87 71 339 285 68 192 749 179 C=O (ketones) Page 10 The Reagent List Shown below is a list of key reagents (not always the whole recipe) which may be useful for solving questions on the exam #1. Reagent classification or specialized use Chapter 13 NaBH‘1 nucleophilic hydride LiAlH4 nucleophilic hydride RMgX nucleophilic carbon RLi nucleophilic carbon Raney Ni desulfurization HSCH2CHZSH thiacetal/thioketal formation 4-CH3C6H4SO3H (TsOH) organic—soluble acid CSHSNH+ ClCrO3' oxidant ClC(O)C(O)Cl/H3CS(O)CH3 then (CH3CH2)3N oxidant HZNNI-I2 hydrazone formation HZNOH oxime formation BF3-O(CH2CH3)2 Lewis acid source (CH3)3C(CH3)2SiCl (TBSCl) protection H39 9H3 Hsc-c—s'rCI H3C CH3 (CH3CH2CH2CH2)4N+F' nucleophilic F‘ source dihydropyran (CSHSO) protection 0 0 Chapter 14 AgZO, NaOH, H20 oxidant Chapter 15 (C4H9)2A1H (DIBAL) Lewis-acidic hydride source Historical HZNNHC(O)NH2 For 216 labs; not for 215 exams HZNNHCéH3(NOZ)2 For 216 labs; not for 215 exams From Chem. 210 0504 oxidation KMnO4 oxidation peroxyacid (e.g., 3—chloroperoxybenzoic acid) oxirane formation 03 then (CH3)ZS or Zn ozonolysis NaNH2 base NaH base K+ 'OC(CH3)3 bulky base HZ/Pd hydrogenation Hz/Pd/CaCO3 hydrogenation BH3 or 9—BBN then HQOZ/NaOH hydroboration PBr3 e.g., R—OH -> R—Br SOCl2 e.g., R-OH —> R-Cl 4-CH3C6H4SOZC1 (TsCl) tosylate formation CH3SOZC1 (MsCl) mesylate formation ...
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This test prep was uploaded on 04/01/2008 for the course CHEM 215 taught by Professor Koreeda during the Fall '07 term at University of Michigan.

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215 Exam-00-1 - Chemistry 2 1 5 First Examination February...

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