The Use of Alkyl Vinyl Ethers in Olefin Syntheses

Abstract

The /3-bromoether synthesis of olefins, as developed by Boord and his coworkers, (2, 6-8) gives many types of olefins almost entirely free of isomers, except the geometric forms; however, the synthesis is lengthy and hence the over-all yields are not very high. By the original procedure, a,ß-dibromoethers were obtained by brominating -chloroethers which were prepared by treating aldehydealcohol mixtures with hydrogen chloride; reaction of the dibromides with Grignard reagents then gave the desired /3-bromoethers. In the past few years simple

Total synthesis of dl-bisnorvernolepin

“…For example, this procedure was repeated on an 80-mm scale and the sample so obtained (20.8 g, 109%) was used directly for the next reaction. Physical data for diester 10 are: R, (200°, 6') 2 min; R/ (silica-2% CH3OH/CHCI3) 0.56, (silica-1:1 ether/hexanes) 0.57; ymax 3310 (m, C=C-H), 1730 (s, C=C>), and 1640 (w, C=C); 1.24 (t, J = 1,6 ), 2.01 (t, 7 = 2.5, 1 H), 2.85 (ABX, 7AB = 18, Avab = 18.5, 7Ax = 7bx = 2.5, 2 H), 2.94 (s, 2 H), 4.12 (q, 7 = 7, 2 H),4.18(q,7 = 7,2H),5.21 (d,7 = 18,1 H),5.23 (d,7 = 11,1 H), 6.00 (d of d, 7dl = 8,7d2 = 11,1 H); m/e 238 (0.9), 199 (10), 193 (17), 164 (16), 137 (10), 125 (13),91 (100).…”

“…Filtration of this mixture through MgSC>4 followed by evaporation afforded essentially pure vinylogous ester 13, 10.05 g (94%), as a yellow oil which was used without purification for the next reaction. R, (170°, 2') 2.2 min; Rf (silica-3% CH3OH/CHCI3) 0.57, (silica-ether) 0.53; iw 1730 (s, C=0), 1650 (s, C=0), and 1610 (s, C=C);6 1.22 (t, J = 7, 3 H), 2.70 (ABX, Ab = 17, ß = 38.4, 2 H split further by Ax = 1.5), 2.80 (ABX, Tab = 17, ß = 39.5, 2 H split further by Ax = 1.5), 3.72 (s, 3 ), 4.13 (q, T = 7, 2 ), 5.16 (d, T = 18, 1 ), 5.19 (d, T = 10.5, 1 H), 5.33 (d,T = 1.5, 1 H), 5.87 (d of d, Tdl = 18, Td2 = 11, 1 H); m/e 224 (4), 196 (3), 179 (8), 150 (100), 137 (4), 123 (12), 109 (14),98 (16),91 (13), 69 (20), 68 (22).…”

“…8 min. The resulting pale yellow solution was stirred for 15 min at 0 °C and then cooled to -78 °C at which time the vinylogous ester 13 (9.73 g, 43.4 mM) in THF (20 mL) was added to the dark red reaction and the mixture then warmed to 0 °C and stirred 10 min during which time it lightened to a bright orange-red color. Solid LAH (1.65 g, 43.5 mM) was carefully added to the reaction over several minutes and the resulting suspension stirred for 10 min at 0 °C (green-brown suspension).…”

“…Physical data for the a alcohol 26 are given as follows: R, (180°, 2') 1.0 min; Rf (silica-3% CH30H/CHC13) 0.53 (silica-2:1 ether/hexanes) 0.33; i/max 3650-3250 (b, OH) and 3570 (sharp, m-w, OH), 1635 (w, C=C), and 1600 (w, C=C); 1.63 ( 2,7 = 14, -ß = 36.9, 2 H, quartet split by 7 , = 10,7 2 = 3.5, Jax, = 5, and J 2 = 3.5), 2.01 (ABX, J ab = 14.5, Avab -60.3, 2 H, split further by J ax -6 and yBX = 4), 2.21 (d, J = 7, 1 H), 2.54 (m, yd| = 10, yd2 = 5, yd, = 3, 1 H), 3.35 (s, 3 H), 3.42 (ABq, yAB = 11.5, / ß = 26.6, 2 ), 4.14 (m.yd] = 6,yd2 = 4,yd, = 7, i h), 4.53 (t,yd] =yd2 = 3.5,1 ),5.12 (d of d, yd, = 18, yd2 = 1.5, 1 H), 5.15 (d ofd, yd| = n,yd2= 1.5, 1 H),5.77(d,y = 3,2 H), 5.89 (d ofd,yd, = 18,yd2= 11,1 H)\m/e 210 (0.1), 192 (0.5), 179 (7), 178 (4), 161 (2), 148 (7), 130(28), 122 (100), 121 (30), 107 (42), 104 (28), 91 (33), 79 (32). Physical data for the ß alcohol are given as follows: R, (180°, 2') 1.0 min; Rf (silica-3% CH3OH/CHCI3) 0.37, (silica-2:1 ether/hexanes) 0.23; i/max 3650-3250 (b, OH), 3590 (sharp, m-w, OH), 1635 (w, C=C), 1600 (w, C=C); b 1.70 (ABX2, J ab = 14, -ß = 23.7, 2 H, split further by Jbx, = 12, J 2 = 4, J ax, = 5, and yAx2 = 2), 1.91 (ABX, Jab -13, Ai>ab -16.5, 2 H, split by yBx = 9, and Jax = 8), 2.35 (broad, s, 1 H,OH),2.40(m,yd| = 12, yd2 = yd3 = 5, OH), 3.34 (s, 3 H), 3.37 (ABq, yAB = 12, /ab = 37.1,2 H), 4.26 (dofd,yd| =9,yd2 = 8, 1 H), 4.67 (d of d, ydl = 4, yd2 = 2,1 ), 5.09 (d of d, yd| = 18, yd2 = 1.5, 1 H), 5.10 (d ofd, ydl = 11, yd2 = 1.5, 1 H), 5.66 (d ofd, yd| = 18, yd2 =11,1 H), 5.67 (m, yd = 5, 2 H); m/e 210 (0.5), 192(1), 179 (4), 178 (8), 161 (10), 148 (13), 130 (8), 122 (100), 121 (21), 107 (42), 104 (13), 91 (22), 79 (24).…”

“…2.7 H), the region between 1.1 to 3.1 excluding the singlet at 1.5 should represent 10 H not the reported 10.9 H, 3.36 (s, 3 H), 3.47 (s, 3 H), 3.67 (broad singlet, 3.1-4.2, ca. 10.6 H, expected 11 H), 4.43-4.79 (m, 3 H), 5.22 (d, T = 18,1 H), 5.28 (d,T= 11, 1 H),6.01 (dofd,Td| = 18, Td2 = 11); m/e 427 (0.2), 411 (0.6), 383 (0.8), 379 (1), 366 (1), 355 (0.9), 342 (2), 323 (3),310 (11), 283 (7), 262 (9), 261 (7), 248 (15),230 (21),204 (10),203 (9), 170 (16), 143 (17), 121 (14), 120 (14), 91 (13), 59 (66), 45 (100), parent not observed at m/e 428.…”