Example 1 Me Me Me Me Me very hindered LTMP(78°C) kinetic enolate amide base LTMP/HMPA thermodynamic enolate LDA 23 LICA LHMDS (PhMe2Si)2NLI 100
Example 1
Example 2 R Z-enolate E-enolate Et LDA Note:As R' becomes sterically Et LTMP 14 more demanding, Z-enolate increases or predominates even LTMP-LiBr 98- best conditions for E-enolate(kinetic) under kinetic conditions P LDA P LTMP 33 LTMP-LiB LDA B Me LTMP 95 Note: As R2 becomes sterically Bu Me LTMP-LiBr 955 Z-enolate only more demanding, E-enolate selectivity increases under kinetic conditions: Ph> Me LTMP LTMP-LiBr Collum J. Am. Chem. Soc. 1991. 113.9571
Example 2
Example 3 OLi RO RO thermodynamic enolate kinetic enolate more stable) R base E Me Me LDA LDA Z559 Me LDA kinetic Me Et LDA/HMPA 84 16 thermodynamic Et LDA 5 Et LDA/HMPA 77 Role of HMPA: increase rate of equilibration, break up enolate aggregation
Example 3
Example 4 LDA LiO Me X Me E-enolate Z-enolate LDA OCH3 95:5 o'Bu Me/R1 1.3-diaxial interaction worse than Me/X A(1, 2)-interaction 77:23 X getting larger, so A(1, 2)steric interaction outweighs the Me/R 1, 3-diaxial interaction NEt
Example 4
4.二羰基化合物的γ-烷基化反应(y- Alkylation of1,3 dicarbonyl compounds 2 equiv. Base R"ⅹ R R R R R R 2)H2O R J.Am.Chem.Soc.,1974,90,1082;1963,85,3237;1965,87,82 Example 1 1)2 KNH2/liq NH3 H82% Me 2)n-BuBr Me 烷基化难易次序: e PhCH2>CH3>-CH2
4. 二羰基化合物的 -烷基化反应( -Alkylation of 1, 3- dicarbonyl compounds) R R' O O 2 equiv. Base R R' O O 1) R"X 2) H2O R R' O O R" J. Am. Chem. Soc., 1974, 90, 1082; 1963, 85, 3237; 1965, 87, 82. Me Me O O 1) 2 KNH2 / liq. NH3 2) n-BuBr Me O O C4H9 82% Example 1 Me O O Me Me O 烷基化难易次序： PhCH2 - > CH3 - > -CH2 -