Chem 634 Professor Fox Exam 1 March 9 2004 1 hour 15 min Your Name KEY Chem 634 Exam 1 March 9 2004 1 Your Name Show the products of the following transformations Mechanistic details are not required but be sure to indicate relative stereochemistry where necessary four parts 5 points each a O OCH3 O 1 BuLi TMEDA 2 TMSCl b H3 C 2 equiv Bu2CuLi CH3 O O NHPh OCH3 TMS H3 C Bu CH3 Chem 634 Exam 1 March 9 2004 1 Your Name continued c 1 EtI Ph3P CO 4FeNa2 2 PhCH2Br CH3 Ph O d O Ph2 But SiO MeMgBr Et Me Ph2 But SiO HO Et Me Me Chem 634 Exam 1 March 9 2004 Your Name 2 The reactions below would not proceed as indicated Provide a brief but detailed explanation and indicate the structure of the product s that would be formed instead of or in addition to the product that is drawn 5 points each O O a mCPBA X O O more substituted carbon migrates O Et b Ph I Et Et 2CuLi LiCN Me THF Ph Et Me Unlike bromides and tosylates the reactions of cuprates with alkyliodides typically occurs with stereochemical scrambling The mechanism is beleived to proceed via electron transfer Thus the other diastereomer shown below is also formed Et Ph Et Me Chem 634 Exam 1 March 9 2004 2 Your Name continued 1 MeLi PhCO2H c deprotonate MeLi 2 H O O MeLi Ph H wkup Me Ph X Me Ph O O Me OH 2Li the dianion is stable and does not decompose until the aqueous workup O Ph Me d CO2 Me CH3 MeO O H3 C 1 LDA X 2 HH Br CO2 Me Br CH3 CO2 Me CH3 Equatorial delivery of the nucleophile Alkylation of exocyclic enolates is dominated by sterics 1 3 Diaxial interactions prevent delivery from the top face Chem 634 Exam 1 March 9 2004 Your Name 3 This question has two parts both of which deal with the reaction below O O O O Et Me CO2Et Me MgBr Me O Et Et 3a Provide an arrow pushing mechanism for the reaction above For this part of the problem it is not necessary to explain the stereochemical aspects of the reaction Just push the arrows and show how the final product is formed 20 points MgBr Me O O O Et Me CO2Et O EtO2C Et Me MgBr O anionic oxyCope O Me O Et Me O O Me Et Me OEt Et O EtO Et Chem 634 Exam 1 March 9 2004 Your Name 3b Provide a detailed model with explains all of the stereochemical aspects stereocenters and alkene stereochemistry 20 points O O O Et Me CO2Et O Me MgBr Me O Et Et note the stereochemistry of the following transformation when detailing your mechanism You may consider this to be general for the reactions of Grignard reagents with ketoesters O OH R MgBr R then H CO2Et O EtO2C Me Et CO2Et EtO2C O Me EtO Me Et Et O O EtO O O O Me Me Et O Et Chem 634 Exam 1 March 9 2004 Your Name 4 Outline a multistep synthesis 20 points HO2C Ph OH Me Ph Me Me Me Retrosynthesis HO2C Ph OR Me Me Selective O Me Claisen Ph Ph Me OH Me enolization Me Me Me Felkin controlled addition oxid Ph O Ph OH Me Me example of an acceptable Forward synthesis Ph Me O BrMg OH DMSO COCl 2 Et3N Ph Me OH Ph Me Me Me EtCOCl pyridine HO2C Ph Me Me warm to rt Me then H3O O Ph OTBS Me Me Me O LDA THF HMPA Ph then TBSCl O Me Me Me
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