Michael Addition Reactions of Unsaturated Esters with Lithium Enolates Derived from Vinylogous Urethanes

Reaction of enamines with trifluoromethyl containing carbonyl reagents

“…The general approach to b 0 -functionalized enamines is the interaction of a preformed lithium derivative of the enamines with carbonyl compounds [3], electrophilic olefins [4] or trimethylchlorosilane [5]. However, in the literature there are examples of uncatalyzed electrophilic reactions proceeding at the methyl group of tertiary push-pull linear enamines, despite the absence of convincing proof of the enamine equilibrium that could rationalize these reactions.…”

“…1 H NMR (300 MHz, C 6 D 6 ): d = 1.28 (3H, t, 3 J HH = 7.2 Hz, CH 3 ), 1.48 (2H, CH 2 ), 2.92 (2H, CH 2 ), 4.13 (2H), 4.69 (1H, CH), 7.31 (2H, CH), 7.65 (2H, CH). 13 C NMR (100 MHz, CDCl 3 ): d= 14.6, 24.7, 36.4, 48.1, 59.7, 78,0 ( 2 J C-F = 27.6 Hz, CCF 3 ), 87,7 127.9 ( 1 J C-F = 288 Hz, CF 3 ), 126,3, 127.9, 128,4, 156.2, 172.5. MC (EI, 70 eV): m/z (%)…”

Acylation of Esters, Ketones and Nitriles

“…(14) The stability of the initially fonned enolates has a crucial bearing on the direction of ring closure. 71 The conformational requirement of the ring closure gives a single diastereomer (20a and 20b) from each diastereomeric ester (19a and 19b; Scheme 21). Diethyl 2-methylheptanedioate (14) cyclizes preferentially through the unsubstituted enolate (15a) rather than the substituted enolate (15b) to give (16) rather than (17).70 This is also the thennodynamic preference since the enolate (16b) is more stable than the enolate (17b) (Scheme 20).…”

“…Treatment of (70) with either sodium methoxide or potassium t-butoxide gives (71), via the enolate of the a,(3-unsaturated ester. Treatment of (70) with either sodium methoxide or potassium t-butoxide gives (71), via the enolate of the a,(3-unsaturated ester.…”