Solvomercuration-demercuration. III. Relative rates of oxymercuration of representative olefins in an aqueous tetrahydrofuran system

Abstract

Complexes of type 10 were generally stable to work-up conditions and repeated recrystallizations. Prolonged exposure to air or heat sometimes resulted in partial decomposition, particularly in those compounds containing halogen on the ring.Yields.-With the exception of 7p, which gave 20-30% yields of cyclohexenone derivatives, more than 70% of the organic substrate was recovered on work-up of reaction mixtures. The bistricarbonyliron complexes presented in Table IV were obtained in yields of <1 to 8% after 3-hr irradiation with a 70-W light source.Greater yields (up to 20%) of 2, 4, 11, and 12 were obtained under the same conditions.Reactions of «-Methylstyrene (7b) under Reflux Conditions. A.-A solution in hexane of 7b (0.9 g) and Fe(CO)s (1.05 g) was irradiated for 0.75 hr with water flow in the inner jacket regulated for mild reflux of the reaction solution. Only Fe(CO)s and Fe3(CO)i2 were detected in ir analysis of the metal carbonyl region, and the bulk of 7b was recovered on work-up.B.-A solution similar to that in part A was irradiated at room temperature for 1 hr, then refluxed with continued irradiation for an additional 0.5 hr. Work-up of the reaction mixture afforded only 7b and a small quantity of 10b.Reaction of «-Methyl-4-phenylstyrene (7k).-A solution of 7k (0.1 g) in 15 ml of hexane was stirred with 1.0 g of Fe2(CO)g for 48 hr under nitrogen. Ir analysis indicated early formation of 8k and Fes(CO)i2. Work-up on a short column of Florisil yielded Fe3(CO)i2 and a mixture of 7k and 8k.Reaction of 2-Bromostyrenetetracarbonyliron (8v).-A solution of 8v (0.5 g) in 110 ml of hexane was irradiated for 6 hr and analyzed by ir monitoring of the metal carbonyl region. After 20 min only a small concentration of 8v was still present while the bands typical of diene-Fe(CO)3 (~2055, 1993, 1983 cm-1, 9v) were at a maximum. Continued irradiation produced bands characteristic of the diiron complex lOv. Preparative tic of the residue after evaporation afforded separation of 2-bromostyrene (7v) and two complexes, one identical by ir and melting point with lOv, and the other identical [mp 120°; vco (hexane) 2070, 2036,2000,1993 cm-1 (sh)] with 13 (see ref 12).Reactions of 4-Chloro-a-methylstyrenetricarbonyliron (9h). A.-A solution of 9h (0.10 g) in 110 ml of hexane was irradiated for 3.75 hr. Consumption of 9h and an increase in bands characteristic of lOh were observed in the ir throughout the irradiation. Work-up of the residue after evaporation gave 7h and a considerably smaller amount of lOh.B. -Heating a solution similar to that in part A at 45°for 1 hr resulted only in a small decrease in the concentration of 9h. At reflux temperature of hexane 9h in this solution decomposed completely within 10 min, and no other organometallic materials were observed.C. -Irradiation of a solution similar to that in part A with 0.5 g of Fe(CO)5 for 2.5 hr yielded lOh at a rate greater than that in part A on comparison of ir concentrations of lOh at any given time.Reaction of «-Methyl-4-phenylstyrenetricarbonyliron (9k).-A so...

Optimal control of molecular fragmentation with homologous families of photonic reagents and chemical substrates

“…Some reaction product yields in traditional chemistry vary systematically with the substrate structure upon interaction with the same chemical reagent. [27][28][29] In particular, chemical reactivity in halogen-containing molecules is typically correlated with the halogen composition of the molecules. [30][31][32] In ref.…”

Controlling factors determining the regiochemistry of intramolecular alkoxymercuration

“…The products from (E)-5-phenylpent-4-en-1-ol were: 2-benzyltetrahydrofuran, 14 1 H NMR and 13 C NMR spectra were obtained with a JEOL JNM α-400 instrument operating at 400 MHz and 100.13 MHz, respectively, in the pulse Fourier mode. Gas chromatographic analyses were performed on a Shimadzu model GC-8AIF with a Carbowax 20M chemical bonded silica capillary column (0.25 mm × 25 m or 11 m) at 120 and 140 ЊC.…”

“…Treatment of the pentenoate with LiAlH 4 in diethyl ether gave (E)-5-(p-methoxyphenyl)pent-4-en-1-ol (2.79 g, 70%), mp 72-74 ЊC; δ H (400 MHz; CDCl 3 ; J values in Hz), 1…”

“…The reaction of (E)-pent-2-ene, which has a symmetrically substituted carboncarbon double bond, preferably yielded pentan-2-ol, but there is no clear explanation of this regiochemistry. 1 In a cyclic system, 3-methylcyclohexene exclusively gave 3-methylcyclohexanol, the regiochemistry of which was explained in terms of the relative stabilities of the two possible regiochemical transition states during the attack of the nucleophiles on their mercurinium ion intermediates. 2 In contrast to the cyclohexene series, the results for the flexible cyclopentenes are not attributable to any reasonable explanation.…”

“…In order to examine the factors determining the regiochemistry of symmetrically substituted carbon-carbon double bonds in the formation of oxacyclic compounds by intramolecular alkoxymercuration, the reaction of (E)-5-phenylpent-4-en-1ol (1), the p-methyl analogue, (E)-5-(p-methylphenyl)pent-4en-1-ol (2) and the p-methoxy analogue, (E)-5-(p-methoxyphenyl)pent-4-en-1-ol (3), were carried out with mercuric acetate and their regioselectivity was compared with that obtained from the methoxymercuration of (E)-β-methylstyrene (4) and (E)-anethole (5). The products were characterized by demercuration with NaBH 4 .…”