CHEM 222 Lecture Notes - Lecture 16: Hydrolysis, Enamine, Carbon Group
17 Mar 2017
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Wittig reaction: ylide: c- (anion) adjacent to + heteroatom (cation, resonance stabilized carbanion functioning as nucleophile. Making ylides: mechanism: sn2, deprotonation of c-h to phosphorus, alkyl halide limited to me, 1o, and 2o (need at least 1 c-h to deprotonate) Practice making ylides: first one is non-stabilized type of ylide (no resonance, second one can be resonance stabilized to some extent, behaves as unstabilized. Stabilized vs. unstabilized ylides: add to different types of molecules, and give different products, stabilized ylides are less reactive as both bases and nucleophiles, phenyl not stabilized. Reagents: alkene + water/acid, r-x, hydrides (h-) + (1) h2o/h, mercuration/demercu. (1) h2o, hg(oac)2 (2) nabh4 (1) h2o/h+ (2) oh, epoxide carbonyl, nabh4, lialh4, hydroboration (1) bh3 (2) h2o2/oh, h2o/h+ (nuh, oh- (nu-, r- (grignards, r-mgbr + carbonyl. Mechanism: alkene --> carbocation (rearrangement, add hg (triangle), no rearrangement, bh2 and h transition state (ant-markovnikov, sn1 (acidic) Sn2 (basic: r- attacks carbonyl, making o-
