Zinc-iron couple induced conjugate addition of alkyl halide derived radicals to activated olefins

Carbohydrate Carbocyclization by a Zinc-Mediated Tandem Reaction and Ring-Closing Enyne Metathesis

“…However, dropwise addition of propargyl bromide to a mixture of 1, zinc, and BnNH 2 in THF under sonication did not provide any enyne product, but instead led to Wurtz-type homocoupling of 1 as the only identifiable product. This dimerization of 1 is known to occur with other zinc sources, 21 but has not been observed before in our reactions. Attempts with added Lewis acids to facilitate the reductive ring-opening led to complex mixtures of products.…”

“…These could be separated by flash chromatography and the major isomer was identified as 1,2,6,7-tetradeoxy-ribo-hept-1,6-dienitol by comparison with literature data. 6a (4S,5R,6R)-5,6-(Isopropylidenedioxy)-4-[(tert-butyldimethylsilyl)oxy]-7-octen-1-yne ( 16) and (4R,5R,6R)-5,6-(Isopropylidenedioxy)-4-[(tert-butyldimethylsilyl)oxy]-7-octen-1-yne (21). The crude product from the tandem fragmentation-propargylation of 1 was dried azeotropically with toluene.…”

High-Affinity Alkynyl Bisubstrate Inhibitors of Nicotinamide N-Methyltransferase (NNMT)

“…β-anomer: 7.02 (d, J = 8.1 Hz, 1H), 6.10 (s, 1H), 5.31 (dd, J = 4.9, 0.9 Hz, 1H), 5.16 (dd, J = 7.2, 4.7 Hz, 1H), 4.64 (td, J = 8.2, 4.6 Hz, 1H), 4.33 (ddd, J = 10.1, 7.1, 2.7 Hz, 1H), 3.81 (s, 3H), 2.66 (ttd, J = 9.6, 4.9, 2.4 Hz, 1H), 2.13 (d, J = 2.4 Hz, 1H), 2.12 (s, 3H), 2.10 (s, 3H), 2.08−2.04 (m, 1H), 2.06 (s, 3H), 2.05−1.97 (m, 1H), 1.84 (ddd, J = 13.1, 9.9, 2.8 Hz, 1H), 1.69− 1.61 (m, 1H), 1.60−1.55 (m, 1H), 1.47 (dddd, J = 13.2, 11.3, 8.9, 4.5 Hz, 1H). 13 C NMR (126 MHz, CDCl 3 ) δ α-anomer: 171.1, 169.9, 169.5, 169.3, 156.9 (q, 2 J C−F = 38 Hz), 115.7 (q, 1 J C−F = 288 68 To a 3-necked flask charged with pyridine (10 mL) were added NaI (1.49 g, 10.0 mmol, 1.0 equiv) and FeCl 3 •6H 2 O (1.35 g, 5.00 mmol, 50 mol %) sequentially, both in one portion. Zinc powder (3.92 g, 60.0 mmol, 6.0 equiv) was added portionwise to the reaction mixture (Caution: exothermic), monitoring the temperature so that it remained below 40 °C.…”

Alkenenitriles: Zn−Cu Promoted Conjugate Additions of Alkyl Iodides in Water

“…Exploratory forays with 1-chloro-4-iodobutane, cyclohexenecarbonitrile ( 6c ), and zinc−copper matrix, under standard conditions,6a afforded the conjugate addition product 7d in 4% yield (Table , entry 1). An intensive screening of solvent, temperature, stoichiometry, ultrasonic irradiation, matrix, and additives identified ambient water as the best medium. Closely monitoring the reaction revealed a rapid initial consumption of 1-chloro-4-iodobutane accompanied by significant formation of 1,8-dichlorooctane, presumably formed by radical−radical coupling.…”