Chem 634 Exam 2 December 10 2007 3 hours Prof Fox Your Name 1 Provide reagents for the following transformation More than one step may be required Do not write mechanisms 2 5 points each O O a O b Ph Ph H Ph O O c Ph O H CO2 Me O d O MeO 2 Provide the products of the following transformations Do not provide mechanisms 2 5 pts each O 1 DIBAL a 2 H3 O MeO cat PdCl2 cat CuCl2 O2 H2O b Ph O c I D Pd 0 Et3N N CH3 TFA d HO 3 Indicate if the following would or would not proceed as written If it will not proceed as written provide the structure of the product that would be formed instead along with a brief explanation 4 pts each 1 MeC OEt 3 cat EtCO2H 2 mCPBA 1 equiv a HO Ph b EtO2C 1 O3 PPh3 Ph 2 KOH O O 1 O O O c 2 TsNH NH2 4 You require a synthesis of 5 from aldehyde 1 Unfortunately the addition of acetylide 2 to aldehyde 1 is not selective it gives a mixture of diastereomers 3 and 4 Luckily diastereomers 3 and 4 are separable by chromatography and can be separately converted into 5 20 pts OH tBuO O tBuO 1 1 2 3 Li 2 separate diastereomers procedure A EtO 2C tBuO OH tBuO 5 procedure B 4 a Outline a stereospecific synthesis of 5 from 3 below b Provide a stereochemical model that explains the stereospecificity of the key transformation in your proposed synthesis 4 You require a synthesis of 5 from aldehyde 1 Unfortunately the addition of acetylide 2 to aldehyde 1 is not selective it gives a mixture of diastereomers 3 and 4 Luckily diastereomers 3 and 4 are separable by chromatography and can be separately converted into 5 20 pts OH tBuO O tBuO 1 1 2 3 Li 2 separate diastereomers procedure A EtO 2C tBuO OH tBuO 5 procedure B 4 c Outline a stereospecific synthesis of 5 from 4 below d Provide a stereochemical model that explains the stereospecificity of the key transformation in your proposed synthesis 5 Provide a detailed arrow pushing mechanism 12 pts HF TMSO O MeO CO2Me N CO2tBu O O H CO 2Me N CO2tBu 6 Provide a detailed arrow pushing mechanism 20 pts Me S Ph S O N AIBN Bu3SnH N OH OH 7 Outline a multistep synthesis 20 pts H MeO2C CO2Me O CH3 CO 2Me CO2 Me
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