(Solved): 13.70 The SN2 reaction between a Grignard reagent and an epoxide works reasonably well when the ep ...

13.70 The SN2 reaction between a Grignard reagent and an epoxide works reasonably well when the epoxide is ethylene oxide. However, when the epoxide is substituted with groups that provide steric hindrance, a competing reaction can dominate, in which an allylic alcohol is produced. Propose a mechanism for this transformation and use the principles discussed in Section 7.9 (substitution vs. elimination) to justify why the allylic alcohol would be the major product in this case below. OH H? g 1) EtMgBr 2) H3O+ Et Major product Minor product A, a cytotoxic marine natural product. Draw the structures of 13.71 The following sequence of reactions was employed during synthetic studies on reidispongiolide compounds A, B, C, and D. Ph 1) CH?=CHMgBr 1) NaH A cat. OsO4 NMO B 2) CH3I C + D Ph 2) H3O+ Ph