25 - CHAPTER 25 Heterocycles Trivial names are commonly...

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CHAPTER 25 Heterocycles
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Trivial names are commonly used for many unsaturated heterocycles:
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Trivial names are commonly used for many unsaturated heterocycles: Nucleophilic ring opening of heterocyclopropanes by Nucleophilic ring opening of heterocyclopropanes by addition at the less substituted ring carbon.
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Four-membered heterocycloalkanes are less strained than their three-membered analogs and therefore require more stringent reaction conditions to open. Heterocyclopentanes and heterocyclohexanes are relatively unreactive. Ring opening may occur by conversion of the heteroatom into a good leaving group (protonation). The heterocyclic cyclopentadienly analogs contain a neutral atom that has one (N) or two (O, S) lone electron pair(s). One of these pairs is delocalized providing the 2 electrons needed for aromaticity (4n+2).
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Pyrroles, furans and thiophenes are prepared from γ -dicarbonyl compounds. An enolizable γ -dicarbonyl compound is treated with an amine derivative (for pyrroles), P 2 O 5 (for furans) or P 2 S 5 (for thiophenes).
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This note was uploaded on 12/26/2008 for the course CHEM CHEM 140C taught by Professor Finn during the Spring '08 term at UCSD.

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25 - CHAPTER 25 Heterocycles Trivial names are commonly...

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