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Solutions to Problems 181 54. (a) HOCH₂CH₂NH₂ (SN2 ring opening) (b) SCH₂CH₃ (Same. Reaction occurs at least substituted CH₃ H carbon of ring.) (c) BrCH₂CH₂CH₂Br (d) ring opening) (e) (SN2 at least substituted ring carbon) (f) DCH₂C(CH₃)₂OH (From attack of D⁻ on less hindered carbon of ring) (g) (From attack of Grignard at less hindered carbon) (h) CH₂CH₂OH (An example of "2-carbon formation of an alcohol two carbons longer than a starting organometallic reagent, by addition to oxacyclopropane) 55. Surprisingly, all but methanol can be made by either hydride or organometallic additions to properly designed oxacyclopropanes. Remember: Anionic nucleophiles always add to the less hindered carbon of the ring. We can carry out retrosynthetic analyses as follows: For any primary alcohol ending in we can use + where Nu = H from or R from either RLi or RMgX. For any secondary alcohol ending in we can use + CH₃ where Nu = H from or R from either RLi or RMgX. Do you see the pattern? For a tertiary alcohol ending in we can use + CH₃ CH₃ where Nu = H from or R from either RLi or RMgX, again. Working forward now, here are reasonable answers. All reactions use (CH₃CH₂)₂O as solvent and are followed by aqueous acid work-up. (b) CH₃CH₂OH (c) or CH₃Li CH₃CH₂CH₂OH (e) CH₃CH₂MgX or CH₃CH₂Li CH₃CH₂CH₂CH₂OH (d) CH₃CHOHCH₃ O (f) or CH₃Li CH₃