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Name________________________________ Sp08_215_E1_p1 I (21 points) Complete the following reactions by providing starting material, reactants (number steps as necessary), or products. a) JOC 2008, 73, ASAP Kobayashi O 1) OsO4 2) Na2SO3 N+ CH3 O 3 HO O THF, H2O OH b) JOC 2008, 73, ASAP Clayden O O CH3 N O N H 3 N H N CH3 OH 3 c) Org. Lett. 2008, 10, 1807 1) CH3CH2CH2CH2Li (base) O H O OCH3 2) [(CH3)2CH]3Si O H3C 3) protonation 3 d) JOC, 2008, 73, ASAP Mandal H3C HO I PhCH2O H O O O NaH + NaI + H2 3 e) Org. Lett. 2008, 10, 1679 HS HCl intramolecular hemiacetal w/ 4-hydroxy SH HO HO H H S S OH + H2O 3 O H cat. acid C15H20O3S2 including 3 6-membered rings + H2O 3 Name________________________________ Sp08_215_E1_p2 II (30 points) A. (JOC 2008, ASAP, Hartung) The reagent 2-chloro-bis[menth-1-yloxycarbonyl]-1,3,2dioxaphospholane was shown to be useful in determining the enatiomeric purity of chiral alcohols via 31P NMR. The enatiomerically pure phosphorous reagent reacts with chiral alcohols to form diasteromers as shown below. The phosphorous diastereomers have baseline-separated signals. Circle the appropriate stereochemical designation for each stereocenter below. R or S R or S H R or S H O H O O O O OH P Cl H O Ph H O O O R or S O O O H H H P O Ph R or S 10 2-chloro-bis[menthy-1-yloxycarbonyl]1,3,2-dioxaphospholane In the meso form of 2-chloro-bis[menth-1-yloxycarbonyl]-1,3,2-dioxaphospholane how many of the eight stereocenters would have the opposite configuration from that shown above? (Circle the correct number below) 0 (it is meso as drawn) 1 2 3 4 5 6 7 8 2 B. (Org. Lett. 2008, 10, 1715) The following transformation was carried out. Fill in the oxidation numbers of the atoms indicated below. How many of the atoms in the aromatic ring were O OCH3 oxidized? (Circle the correct number) 5 steps NH N 0 1 2 3 4 5 6 N N O N OCH3 H How many of the atoms in the aromatic ring were O reduced? (Circle the correct number) 0 1 2 3 4 5 6 6 6 C. Provide the IUPAC name for the following molecules H HO H3CO O OH H H 6 Name________________________________ Sp08_215_E1_p3 III (24 points) A. (JOC 2008, ASAP, Shaabani) "The following reaction includes some important aspects like the use of water as a reaction component and a 'green' reaction medium, high atom economy, and mild reaction conditions." O O NC NH2 TsOH 2 + N C + H O + 2 NH NH HN 16-24 hr NC NH2 2,3-diaminomaleonitrile NC CN The authors propose a multistep mechanism that begins with the "formation of diimine 6 from condensation between DAMN and ketones." DAMN is 2,3-diaminomaleonitrile. NC NH2 + 2 O NC NH2 2,3-diaminomaleonitrile NC N NC N + 2 H2O diimine 6 Show the mechanism of formation of one of the imines. Use HB as the catalytic acid and B- as its conjugate base. NC NH2 + NC O H-B NH2 NC N NC NH2 monoimine 18 B. Provide the IUPAC name for the following molecule: HO OH O 6 Name________________________________ Sp08_215_E1_p4 IV (24 points) A. (JOC, 2008, ASAP, Loh) Chemists have been studying the Barbier-Grignard reactions with the goal of affecting the carbon-carbon bond forming reaction in solvents like water. Recent developments include the use of indium metal catalysts that react through single electron transfer mechanisms. Show the product of the following reaction: i) O In/CuI/I2 1) Mg + OR I H H2O, 2 days 2) protonation 3 ii) The indium catalyst is also very effective for coupling cyclohexyl iodide with 4-bromobenzaldehyde as shown below. Why would the Grignard reagents [1) Mg + 2) protonation] be a poor choice for this coupling reaction? (Use structures of possible products and words to explain.) O 1) Mg ??? I H + 2) protonation Br 5 B. (JOC, 2008, 73, 2592) The authors of this paper were studying the biosynthesis of 1,1dihalogenated 1-alkenes via an anti-periplanar E2 elimination of HBr using 1,1-dibromo-1-chlorobutane as their model. The products of the elimination reaction are diastereomers. Draw them: i) Cl ii) + E2 elimination of HBr Br Br Z-isomer E-isomer 4 Draw Newman projections of the three possible staggered conformers of 1,1-dibromo-1-chlorobutatne looking at the first carbon down the C1-C2 bond. iv) iii) vi) Which conformer leads to the Z-isomer? (Circle one) v) X Y Z 3 Conformer X 3 Conformer Y 3 Conformer Z 3 Name________________________________ Sp08_215_E1_p5 V (21 points) (JOC, 2008, ASAP, Li) The authors of this paper describe an acid catalyzed intramolecular Friedel Crafts Alkyation. A key intermediate in the reaction mechanism is the carbocation resulting from the loss of water. Product A is the only product. The carbocation intermediate leading to product B does not form due to the steric interactions. I I H2SO4 I OH Product A Product B a) Draw the three major resonance contributors of this carbocation intermediate: (rotation around a C-C bond may lead to one or more of the resonance contributors) Resonance contributor leading to Product A Resonance contributor leading to Product B 9 b) The reaction rates were correlated with the predicted relative stability of the corresponding carbocations; rank the expected order of carbocation stability. Start with the least stable carbocation. Briefly explain your ranking. OCH3 I OH Alcohol A least stable carbocation derived from A-D I I OH Alcohol C Alcohol B < OH < < I OH Alcohol D most stable carbocation derived from A-D Briefly explain your ranking 12