New Compounds. Some Acetylenic Compounds

Mechanistic studies of 2-lithio-1,3-dithiane reactions with radical probes

“…This material was identical by IR and NMR with a sample prepared independently from ethanolammonium chloride by ion exchange (Dowex 1-X8, N02" form), and it gave a positive ferrous sulfate ring test for nitrite.25 Addition of a solution of oxalic acid dihydrate (70.3 mg, 0.558 mmol) in absolute ethanol (2.0 mL) to a solution of nitrite 5 (76.0 mg, 0.703 mmol) in absolute ethanol (3.0 mL) caused the precipitation of ethanolammonium oxalate (56.0 mg, 0.264 mmol, 75.1%). Recrystallization from aqueous ethanol provided material melting at 197-198 °C dec (lit.26 mp 199-200 °C dec), which was identical by IR and mixture melting point with an authentic sample.26 Hydrazinolysis of 2-Methyl-4-nitro-lif-imidazole-lethanol (7). A solution of 2-methyl-4-nitro-lH-imidazole-1ethanol (7; 100 mg, 0.584 mmol) in hydrazine (6.3 mL, 95%) was heated under Ar for 6 days at 60 °C.…”

“…The ratio of the regioisomers for a given ,ß-unsaturated carbonyl has been found to be dependent on the nature of the carbon nucleophile (hard or soft), the counterion (ion association vs. carbonyl activation control), and the reaction conditions such as solvent and temperature (kinetic vs. thermodynamic control).2 For example, in reversible reactions, the [1,2] and [1,4] adducts are usually the results of kinetic and thermodynamic control, respectively.3 Reversible additions are normally observed with carbanions that are well stabilized or highly delocalized (i.e., high level of HOMO),4 and the reversibility is often promoted by high reaction temperature3,5 or high solvent polarity.5,6 Even for kinetically controlled reactions, the nature of the solvent, e.g., the addition of HMPA, has been found to have a crucial effect in determining regioselectivity. 7 The reasons for the change in regioselectivity caused by the addition of HMPA in these reactions are not clear, although a number of possible explanations may be offered. HMPA perhaps makes the addition process reversible by virtue of its cation-solvating ability.8 It is also possible that the carbonyl activation by the counterion becomes insignificant in the presence of HMPA, thus making [1,4] addition more favorable.4 Another possibility is that HMPA perturbs the highest occupied molecular orbital (HOMO) of the nucleophile in some manner favoring conjugate addition over [1,2] addition.9 Eliel et al have observed that HMPA causes upfield shifts of the phenyl proton and carbon resonances in their NMR study of 2-lithio-2-phenyl-l,3-dithiane.10 They have suggested that the observed shifts are due to the ion-pairing change, namely, a contact ion pair in THF vs. a solvent-separated ion pair in the presence of HMPA.…”

“…Caled for C14H18OS2: C, 63.16; H,6.77. Found: C, 63.60; H, 6.56. The reaction of 4b with 8 similarly produced 9b: mp 90-92 °C; IR (CHClg) 3510, 3060, 3010, 2910, 1660, 1595, 1480, 1440, 1325, 1225, 1150, 1030 cm'1; 7H NMR 8 0.20 (m, 2 ), 0.82 (m, 2 ), 1.27 (m, 1 ), 1.75 (m, 2 H), 2.56 (m, 4 ), 3.10 (s, 1 H), 7.18 (m, 8 ), 7.61 (m, 2 H); 13C NMR 8 141.5, 136.9, 132.2, 128.3, 127.6, 127.3, 127.0,126.1, 79.2, 74.0, 27.7, 27.4, 24.7,17.3, 5.4, 0.90; MS, m/z (relative intensity) 342 (M+, not present), 301 (0. Deuterium Oxide Quenching Experiments.…”

“…The pure product 11 was obtained by preparative TLC (10% diethyl ether in hexane on Si02): oil; IR (CHClg) 3510, 3350, 2950, 2900,1640,1460,1420,1350,1195, 1095, 1005 cm'1; !H NMR 1.12 (s, 9 ), 1.22 (s, 9 ), 2.00 (m, 2 H), 2.87 (m, 5 H), 4.29 (s, 1 H), 5.45 (q, 2 H, J = 13.5 Hz); 13C NMR 142.7,127.5, 81.8, 59.5, 39.8, 32.6, 31.7, 29.7,26.7, 25.6; MS, m/z (relative intensity) 288 (M+, not present), 231 (1.4), 202 (0. The reaction of 4b with 10a similarly produced 12: mp 40-41 °C; IR (CHClg) 3050, 2960, 2900, 1700, 1590, 1480, 1420, 1360, 1275,1215,1060 cm"1; NMR 0.62 (s, 9 ), 1.25 (s, 9 ), 1.83 (m, 2 ), 2.35-3.0 (m, 6 H), 3.85 (m, 1 ), 7.30 (m, 3 ), 8.10 (m, Acknowledgment. We thank the Robert A. Welch Foundation (Grant A-752) for the financial support of the research.…”

The preparation of esters of formic acid using boron oxide

“…Concentrated sulfuric acid is not appropriate since formic acid is unstable under these conditions. In an adaptation of the procedure of Heaton and Noller (9) for the preparation of 'Present address: Taitoniekantie 9 D 214,40740 Jyvaskyla, Finland. '~uthor to whom correspondence may be addressed.…”