Recent progress in transition metal-catalyzed stereoselective synthesis of acyclic all-carbon tetrasubstituted alkenes

Divergent Synthetic Access toE- andZ-Stereodefined All-Carbon-Substituted Olefin Scaffolds: Application to Parallel Synthesis of (E)- and (Z)-Tamoxifens

“…A literatures urvey revealed few E-a nd Z-stereoretentive reactions of either a-alkyl-o ra ryl-substituted a,b-unsaturated esters. [1] Scheme 4s hows the success of the derivatization array.N on-markedc ompounds 7-10 are known, whereas compounds 11-14 are novel. The reactionc onditions can be summarized as follows:[ a] acid hydrolysis gave acids (E)-7 and (Z)-7; [15] [b] DIBALr eduction afforded allyl alcohols (E)-8 and( Z)-8; [16] [c] MnO 2 allylic alcohol oxidationo f( E)-8 and (Z)-8 yielded aldehydes (E)-9 and (Z)-9,r espectively; [16a] [d] dimethyl alcohols [b] 1Me…”

“…The obtained crude product was purified by SiO 2 column chromatography (hexane/AcOEt 100:1) to give (E)-5a-1 as ac olorless oil (118 mg, 82 %, E/Z = 96:4). 1 8, 14.0. 22.3, 22.4, 27.6, 30.8, 31.2, 31.7, 36.4, 51.4, 126.8, 127.8 (2C) [14] PhMgBr (0.92 mL, 1.00 mL;1 .09 m in THF) was added to as tirred suspension of ZnCl 2 (136 mg, 1.00 mmol) in THF (0.50 mL) at 0-5 8C under an Ar atmosphere, and the mixture was stirred at the same temperature for 0.5 h. Enol tosylate (Z)-4a [5] (191 mg, 0.50 mmol) in THF (0.5 mL) and [Pd(dppb)Cl 2 ]( 3.0 mg, 0.005 mmol) were successively added to the mixture, which was then stirred at 60-65 8Cf or 2h.A fter cooling to room temperature, aq.…”

“…8, 17.4, 22.6, 30.9, 35.9, 51.4, 124.5, 126.9, 127.7 Method B:F ollowing the procedure for the preparation of (Z)-5a-1,t he reaction of enol tosylate (Z)-4'c (163 mg, 0.50 mmol) using PhMgBr (10.4 mL, 1.00 mmol;0 .96 m in THF), ZnCl 2 (136 mg, 1.00 mmol), and [Pd(dppb)Cl 2 ]( 3.0 mg, 0.005 mmol) gave the desired product (Z)-5c'-1 as ac olorless oil (79 mg, 70 %, E/Z = 2:98). 1 HNMR (500 MHz, CDCl 3 ): d = 0.85 (t, J = 6.9 Hz, 3H), 1.24-1.33 (m, 4H), 2.03 (s, 3H), 2.45 (t, J = 6.9 Hz, 2H), 3.36 (s, 3H), 7.08-7.11( m, 2H), 7.22-7.31 ppm (m, 3H); 13 CNMR (125 MHz, CDCl 3 ): d = 13. 8, 15.8, 22.5, 29.6, 34.6, 51.1, 125.7, 126.8, 127.2 (2C) 13.7, 22.3, 23.4, 30.7, 31.3, 51.3, 55.1, 113.6 (2C), 128.3 (2C), 130.5, 135.3, 143.1, 158.5, 170.7 ppm;I R (neat): ñ max = 2955, 2837, 1715, 1609, 1508, 1244, 1134, 1032, 831 9, 20.8, 22.6, 30.6, 30.8, 51.2, 55.1, 113.4 (2C), 128.1 (2C), 131.…”

“…Method A:F ollowing the procedure for the preparation of (E)-5a-1,t he reaction of enol tosylate (E)-4d (156 mg, 0.50 mmol) with PhMgBr (0.92 mL, 1.00 mmol;1 .09 m in THF), ZnCl 2 (136 mg, 1.00 mmol), and [Pd(dppe)Cl 2 ]( 5.8 mg, 0.01 mmol) gave (E)-5d as acolorless oil (37 mg, 34 %, E/Z = 96:4]. 1 HNMR (500 MHz, CDCl 3 ): d = 1.00 (d, J = 7.5 Hz, 6H), 1.99 (s, 3H), 2.54 (septet, J = 7.5 Hz, 1H), 3.82 (s, 3H), 7. 14-7.17 (m, 2H), 7.25-7.30 (m, 1H), 7.33-7.38 ppm (m, 2H); 13 CNMR (125 MHz, CDCl 3 ): d = 21.4 (2C), 23.3, 29.8, 51.2, 126.9, 127.2 (2C), 128.3 (2C), 136.8, 137.3, 142.2, 170.5 ppm;I R( neat): ñ max = 2964, 1723, 1599, 1492, 1433, 1301, 1243, 1143…”

“…The impressive progress in this area has been comprehensively reviewed. [1] The strategyf or the synthesis of acyclicf ully-substituted olefins is generallyc ategorized into five approaches:1 )carbometalations of alkynesu sing Cu, B, Sn, Mg, Pd, and so forth, followed by reactions with electrophiles, 2) acid-induced carbonyl olefinations of unsymmetrically substituted ketones,3 )elimination reactions of tertiary alcohols, 4) cross-metatheses between olefins, and 5) ynolate-mediatedr eactions derived from a,a-dibromoesters.…”