Gativeinductivee ct resonance wins out n ne ffe

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Unformatted text preview: hdrawing: C , C , C N, NO FR NO F I nductive : CF F O CR H2 C C H O CR O CR H2 C C H O CR H2 C C H O CR 90% Re sonance : Exam : ple + Δ Doe not com tewith die s pe nophile re : lative e ly -rich. S eExam s of theTre in Re om ple nd activity of Die nophile and Die s s ne H3 C < < F3 C < Die nophile H3 C H3 C H3 C Diene Increasing reactivity NC < NC NC < < < H 3CO Mechanism: Concerted + Δ Orbital de scription: sp2 sp2 sp3 Die ls-Alde re r action re quire acce s ssing thele stables-cis ss conform ation CH3 CH3 H3C CH3 H s-cis s- tr ans s-cis s-tr ans Whe s-cis formis hinde d or n re im possible there , action slows or doe not s occur. Whe die is constraine s-cis, the n ne d t ransform ation is acce rate . le d Consequences of Concertedness Consequences S re cific: Re ntion of Die te ospe te nophile S re m te oche istry (ne C w —Cbonds gre n) e O CO CH 3 O CC3 OH 80% + CH3 C3 H C is O COCH 3 C (race ic) is m O COCH 3 90% + H 3C CH3 Trans Trans (race ic) m Re ntion of Die S re m te ne te oche istry Re OCH 3 N C CN OCH3 + OCH 3 Trans,trans Trans,trans (sam for cis,cis-die ) e ne (sam N C CN CN CN CN CN OCH3 O CH3 OCH 3 N C CN + OCH 3 C is,trans N C CN CN CN CN CN H 3CO Whe both partne areste oche ically de d: “Endo rule n rs re m fine ” Whe de rm s the approach. te de ine ir Endo/Exo Addition Endo/Exo S ubstitue point away nts f romdie ne S ubstitue...
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