Chem 634 Professor Fox Exam 1 Fall 2007 3 hours Your Name 1 Provide conditions for the following transformations Mechanistic details are not required 4 points each a 1 BuLi 2 NaH 3 Br O CO2 Me O CO2 Me 4 H CO2Me 1 LDA HMPA b CO2 Me 2 MeI c 1 O H 2 O MgBr OMe NMe2 OMe NEt2 2 Indicate whether the reactions below would proceed as indicated Provide a brief but detailed explanation If the product does not proceed as shown indicate the structure of the product s that would be formed instead of or in addition to the product that is drawn 4 points each a O mCPBA x OAc NO Baeyer Villiger proceeds with retention O O b O OAc O 1 KH H 2 Ph Ph H Br Ph O H Also formed NO would give a mixture of C and O alkylation c tBu LiAlH4 O tBu x OH NO LAH delivers hydride from axial face to give the equatorial alcohol tBu OH tBu OH 3 Provide a detailed arrow pushing mechanism O 15 points 2 Mn OAc 3 HOAc H CO2Me H O H O CO2Me CO2Me O CO2Me O H AcO Mn OAc OAc Mn OAc AcO CO 2Me O O CO 2Me electron transfer to Mn OAc 3 H O CO2Me CO2Me O CO2 Me H H H O CO2 Me O CO 2Me 4 This question has two parts both of which deal with the reaction below CCl3 OH Me cat NaH Et O NH Me Et Cl3C C N a 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 10 points CCl3 OH Me Et cat NaH O NaH Me NH Et Cl3C C N CCl3 Cl3C C N O O Me Et Me Et CCl3 CCl3 O Me H O N O NH Et Me NH Et Me Et 4 This question has two parts both of which deal with the reaction below CCl3 OH Me cat NaH Et O NH Me Et Cl3C C N b Provide a detailed model with explains all of the stereochemical aspects stereocenters and alkene stereochemistry 10 points CCl3 O CCl3 NH Me Et H NH Me Et CCl3 CCl3 H Me Me O O NH Et O NH Claisen via Chair TS Et 5 Provide a multistep synthesis starting from A 16 points O OH A 1 H2 NtBu 2 EtMgBr tBu N 1 I Felkin product MgBr 2 H3O O OH CrO3 H LiiBu3 BH OH O 6 Compound 1 does not react when heated However reduction of the lactone gives 2 which rearranges to 3 upon heating HO HO no reaction OMe O MeO H OH MeO O H OH LiAlH4 OH OH OH H 1 3 2 a provide an arrow pushing mechanism OMe OMe H OH H OH H 3 OH OH OH 2 OH b provide a stereochemical model that explains why 1 does NOT undergo a Cope rearrangment HO HO O MeO 1 O MeO O O Cope rearrangement of 1 would produce a cyclic molecule with two transbonds The product would be excessively strained Because of the lactone constraint 1 cannot adopt a conformation that would lead to cis double bonds c provide a model that explains the stereospecificity in the formation of 3 HO single bond rotations OH MeO H OH HO OH MeO OH H HO MeO OH OH s cis 2 Compound 2 can rotate single bonds to adopt a single bond cis conformation which can undergo the Cope rearrangement to produce cis single bonds OMe H OH H OH OH 3
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