Neighbouring-group Influence on the Ring Opening
1747
(C(OEt)2) ppm; MS (EI): m=z (%) ¼ 195 (Mþ-OEt, 100), 127 (93); HRMS (EI): m=z calcd for Mþ-
OEt, C10H17O, 195.1749; found 195.1765.
4c: IR (film): ꢀꢀ¼ 2927s, 2861s, 2241w, 1459m, 1358m, 1331m, 1260w, 1152s, 1057s, 1009s,
1
910w, 811wcmꢃ1; H NMR (200 MHz, CDCl3): ꢁ ¼ 0.85–0.91 (m, CH3), 1.20–1.60 (m, 18H), 2.24
(dt, J ¼ 7.0, 1.6 Hz, CH2), 3.49–3.82 (m, 2 CH3CH2O), 5.26 (t, J ¼ 1.6 Hz, ((EtO)2CH) ppm; 13C NMR
(50 MHz, CDCl3): ꢁ ¼ 13.9 (CH3), 14.9 (2 CH3CH2O), 18.4 (CH2), 22.4 (CH2), 28.1 (CH2), 28.7
(CH2), 28.8 (CH2), 29.0 (CH2), 31.6 (CH2), 60.3 (2 CH3CH2O), 75.4 (C), 86.3 (C), 91.3 ((EtO)2CH)
ppm; MS (EI): m=z (%) ¼ 240 (Mþ, 1), 195 (Mþ-OEt, 100), 81 (45), and 55 (55); HRMS (EI): m=z
calcd for Mþ-OEt, C10H17O, 195.1749; found 195.1721.
3,3-Diethoxy-5-phenylpent-1-yne (3d, C15H20O2)
and 1,1-Diethoxy-5-phenylpent-2-yne (4d, C15H20O2)
Cyclopropane 2d (1.91 g, 5.0mmol) afforded a mixture of 3d and 4d in a 40:60 ratio (GC analysis).
Subsequent purification by flash chromatography (a 96:4 mixture of n-hexane and ethyl acetate)
yielded pure, yellowish samples of 0.23g 3d (20%) and 0.40g 4d (34%).
3d: IR (film): ꢀꢀ¼ 3287m, 3027m, 2975s, 2932s, 2890m, 2112w, 1600w, 1494w, 1450m, 1389m,
1292m, 1274m, 1222m, 1167s, 1114s, 1053br, 1009s, 961m, 878w, 822w, 745m, 700s, 659mcmꢃ1
;
1H NMR (200 MHz, CDCl3): ꢁ ¼ 1.22 (t, J ¼ 7.1 Hz, 2 CH3CH2O), 2.09–2.17 (m, 2H), 2.58 (s, ꢄCH),
2.79–2.88 (m, 2H), 3.52–3.79 (m, 2 CH3CH2O), 7.12–7.32 (m, Ph) ppm; 13C NMR (50MHz, CDCl3):
ꢁ ¼ 15.0 (2 CH3CH2O), 30.4 (CH2), 39.6 (CH2), 58.0 (2 CH3CH2O), 73.2 (ꢄCH), 80.8 (ꢄC), 98.0
(C(OEt)2), 125.7 (CH), 128.2 (4 CH), 141.4 (C) ppm; MS (EI): m=z (%) ¼ 187 (Mþ-OEt, 35), 127
(56), 91 (100), 77 (21); HRMS (EI): m=z calcd for Mþ-OEt, C13H15O, 187.1123; found 187.1142.
4d: IR (film): ꢀꢀ¼ 3062w, 3028m, 2976s, 2928s, 2887s, 2240w, 1605w, 1494m, 1449m, 1357s,
1
1334s, 1150s, 1056br, 1009s, 911w, 746m, 700scmꢃ1; H NMR (200MHz, CDCl3): ꢁ ¼ 1.21 (t,
J ¼ 7.2 Hz, 2 CH3CH2O), 2.49–2.58 (m, 2H), 2.81–2.88 (m, 2H), 3.45–3.76 (m, 2 CH3CH2O), 5.24
(t, J ¼ 1.7 Hz, (EtO)2CH), 7.16–7.33 (m, Ph) ppm; 13C NMR (50 MHz, CDCl3): ꢁ ¼ 14.9
(2 CH3CH2O), 20.6 (CH2), 34.4 (CH2), 60.4 (2 CH3CH2O), 76.2 (C), 85.3 (C), 91.2 ((EtO)2CH),
126.1 (CH), 128.16 (2 CH), 128.18 (2 CH), 140.2 (C) ppm; MS (EI): m=z (%) ¼ 232 (Mþ, 1), 91 (100),
77 (8); HRMS (EI): m=z calcd for Mþ-OEt, C13H15O, 187.1123; found 187.1150.
3,3-Diethoxy-4-cyclohexylbut-1-yne (3e, C14H24O2)
and 1,1-Diethoxy-4-cyclohexylbut-2-yne (4e, C14H24O2)
Cyclopropane 2e (1.91 g, 5.0mmol) afforded a product mixture of 3e and 4e in a 36:64 ratio (1H NMR
analysis). Subsequent purification by flash chromatography (a 95:5 mixture of n-hexane and ethyl
acetate) yielded 0.64 g (57%) of a pure, yellowish sample of the two alkynes, from which 0.40 g 4e
(34%) were isolated. IR (film): ꢀꢀ¼ 2975s, 2925s, 2855s, 2242w, 1448m, 1331m, 1152s, 1055s, 1007s,
1
912m, 817wcmꢃ1; H NMR (200 MHz, CDCl3): ꢁ ¼ 0.83–1.83 (m, 17H), 2.14 (dd, J ¼ 6.8, 1.7Hz,
CH2), 3.50–3.82 (m, 2 CH3CH2O), 5.27 (t, J ¼ 1.7 Hz, (EtO)2CH) ppm; 13C NMR (50 MHz, CDCl3):
ꢁ ¼ 15.0 (2 CH3CH2O), 25.9 (2 CH2), 26.1 (CH2), 26.3 (CH2), 32.6 (2 CH2), 36.9 (CH), 60.2
(2 CH3CH2O), 76.4 (C), 85.2 (C), 91.4 ((EtO)2CH) ppm; MS (EI): m=z (%) ¼ 223 (Mþ-H, 10), 179
(Mþ-OEt, 100), 55 (41); HRMS (EI): m=z calcd for Mþ-OEt, C12H19O, 179.1436; found 179.1441.
Attempts to isolate a pure sample of 3e were unsuccessful. The compound was therefore made by
independent synthesis (vide infra).
3,3-Diethoxy-5-methylhex-1-yne (3f, C11H20O2)
and 1,1-Diethoxy-5-methylhex-2-yne (4f, C11H20O2)
Cyclopropane 2f (1.68 g, 5 mmol) gave a product mixture of 3f and 4f in a 22:78 ratio (GC and
1H NMR analyses). Subsequent work-up by flash chromatography (n-hexane:ethyl acetate ¼ 97.5:2.5)
afforded 0.33g of a yellow liquid, which consisted of almost pure 4f (36%), but contained traces of
both 3f and an aldehyde [2, 3]. IR (film): ꢀꢀ¼ 2964s, 2928br, 2241w, 1462m, 1361m, 1334m, 1279w,
1257w, 1151s, 1058br, 1009s, 911w, 817br cmꢃ1; 1H NMR (200MHz, CDCl3): ꢁ ¼ 0.98 (d, J ¼ 6.5 Hz,