Page 35 - Advanced Organic Chemistry Part B - Reactions & Synthesis

Scheme 1.1. Composition of Enolate Mixtures Formed under Kinetic and Thermodynamic 7
Control a
SECTION 1.1
O – O – O – Generation and
1 O Properties of Enolates
CH 3 CH 2 CH 2 CH 3 CH 3 and Other
CH 3 CH 2 CCH 3 CH 3 Stabilized Carbanions
CH 3
Kinetic,
(LDA 0° C) 71% 13% 16%
2 – – O –
O O O
CH (CH )
3
2 2
CH 3 (CH 2 ) 3 CCH 3 CH CH 3
CH 3 (CH 2 ) 3 CH 2 3
2 2
Kinetic CH 3 (CH )
(LDA –78°C) 100% 0% 0%
Thermodynamic
(KH, 20°C) 42% 46% 12%
3 – O O –
O
CH 3
(CH 3 ) 2 CH CH 3
(CH 3 ) 2 CHCCH 3 CH 2
CH 3
Kinetic
(KHMDS, –78°C) 99% 1%
Thermodynamic
(KH) 88% 12%
– O – O O –
4 b O CH 3
CH 3
(CH 3 ) 2 CH (CH 3 ) 2 CH CH 2 CH 3
(CH 3 ) 2 CHCCH 2 CH 3
CH 3 Z
E CH 3
Kinetic
LDA 40% 60% 0%
LTMP 32% 68% 0%
LHMDS 2% 98% 0%
2% 98% 0%
LiNHC 6 H 2 Cl 3
5 O O – O –
PhCH
PhCH 2 CCH 3
PhCH 2 CH 2 CH 3
E,Z- combined
Kinetic
(LDA 0°C) 14% 86%
Thermodynamic
(NaH) 2% 98%
6
O O – O –
CH 3 CH 3 CH 3

Kinetic
(LDA, 0°C) 99% 1%
Thermodynamic
(NaH) 26% 74%
(Continued)