- Dehydrochlorination of 2-chloroethanol, 2-chloro-1-propanol, 1-chloro-2-propanol, 2-chloro-2-methyl-1-propanol and 1-chloro-2-methyl-2- propanol
-
The reactions between a few 1,2-chlorohydrins and sodium hydroxide have been studied and shown to involve a two-step nucleophilic elimination of hydrogen chloride. The data are given for the slow rate-determining step of 2-chloroethanol 1, 2-chloro-1-propanol 2, 1-chloro-2- propanol 3, 2-chloro-2-methyl-1-propanol 4 and 1-chloro-2-methyl-2-propanol 5. Compounds 4 and 5 gave 2-methyl-1,2-propanediol as the final product instead of oxiranes given by compounds 13. In contrast to some earlier reports the mere water reaction was shown to be almost negligible. In constant ionic strength the base concentration had no effect on the rates whereas at different base concentrations (0.0500.250 mol dm-3) alone the rate of alkaline dehydrochlorination of 1 clearly decreased (103k2, dm 3 mol-1 s-1: 10.0-8.7, respectively). The rate of 2 at constant base concentration (0.010 mol dm-3) and at different ionic strengths (dm3 mol-1: 0.010-0.500) decreased also (103k2, dm3 mol-1 s-1: 76-65, respectively) indicating that the decrease is mainly due to the change in the ionic strength also in the former case. ARKAT-USA, Inc.
- Pihlaja, Kalevi,Kiuru, Marja-Leena,Sippola, Anne
-
p. 120 - 133
(2013/09/24)
-
- Use of xanthine derivatives for reducing the pathological hyperreactivity of eosinophilic granulocytes, novel xanthine compounds and process for their preparation
-
Use of xanthine derivatives for reducing the pathological hyperreactivity of eosinophilic granulocytes, novel xanthine compounds and process for their preparation. Tertiary 1-(hydroxyalkyl)-4-alkylxanthines are suitable for the production of pharmaceuticals for the treatment of disorders which is associated with a pathologically increased reactivity of eosinophilic granulocytes. Novel xanthine derivatives and process for their preparation are described.
- -
-
-
- A novel and efficient alkyl radical trap in aqueous medium
-
A simple water soluble diselenide derivative 1 shows radical scavenger properties towards alkyl and hydroxyl radicals (k3 (0°C)=6.8x108 M-1 s-1) in Fenton-type chemistry. The reaction rate between produced alkyl radicals 2 and the diselenide overwhelms self-termination and halogen transfer reactions.
- Barton, Derek H. R.,Jacob, Marc,Peralez, Eric
-
p. 9201 - 9204
(2007/10/03)
-
- The return of the succinimidyl radical
-
The aqueous kinetics of the succinimidyl radical, S., has been re-examined in the presence of oxidizable substrates and oxygen. The results indicate a rapid equilibrium between S. and its ring-opened analogue, the β-(isocyanato-carbonyl)ethyl radical, PI.. The equilibrium constant K1 is ca. 10, with k1 ≈ 107 s-1 and k-1 ≈ 106 s-1. The glutarimidyl radical, G., was produced by one-electron reduction of N-chloroglutarimide, GCl. The rate constants of several oxidation and hydrogen abstraction reactions with S. and G. have been determined. Furthermore, halogen abstraction reactions from haloimides by some selected alkyl radicals were also scrutinised. Most striking is the finding that the 2-cyanoethyl radical abstracts Br from SBr ca. 25 times slower than does the ethyl radical. This demonstrates a strong β-effect and rationalises a relatively slow Br abstraction rate by PI. from SBr. While the closure rate of the PI' radical appears to be solvent-insensitive, the ring opening rate of S., k1, is estimated to be ca. 100 times faster in, e.g., CH2Cl2 than in water. This suggests hydrogen-bonded stabilisation of S.. Acta Chemica Scandinavica 1998.
- Merenyi, Gabor,Lind, Johan,Eberson, Lennart
-
-
- Studies on steric and electronic control of 2'-3' phosphoryl migration in 2'-phosphorylated uridine derivatives and its application to the synthesis of 2'-phosphorylated oligouridylates
-
For the synthesis of 2'-phosphorylated oligouridylates by use of new phosphoramidite building units, several masked phosphoryl groups have been examined as 2'-phosphate precursors, which should not be migrated to the 3' position when the 3' hydroxy protecting group must be removed to introduce a phosphoramidite residue into the 3'-position. As a consequence, bis(2-cyano-1,1-dimethylethoxy)thiophosphoryl (BCMETP) was found to be the most suitable 2'-phosphate precursor. This thiophosphoryl group could be introduced into the 2'-hydroxyl of 3',5'-silylated uridine derivative 7 by phosphitylation with bis(2-cyano-1,1-dimethylethoxy)(diethylamino)phosphine followed by sulfurization. Treatment of the 2'-thiophosphorylated product 15 with (HF)(x)·Py in THF gave exclusively the 3',5'-unprotected uridine derivative 16a. Compound 16a was converted to the phosphoramidite unit 22 via a two-step reaction. This building block was used for the solution phase synthesis of U(2'-p)pU (29) and U(2'-ps)pU (30). Both the 2-cyano-1,1-dimethylethyl and 2-cyanoethyl groups were effectively removed from the fully protected derivative 25 by treatment with DBU in the presence of N,O-bis(trimethylsilyl)acetamide (BSA). The resulting 2'-thiophosphoryl group was successfully converted to a phosphoryl group by iodine treatment to give U(2'-p)pU (29). U(2'-ps)pU (30) was also synthesized by a modified procedure without the iodine treatment. Reaction of 29 with a new biotinylating reagent in aqueous solution in the presence of MgCl2 gave a biotin-labeled product 35 having a pyrophosphate bridge at the 2' position. Reaction of 30 with monobromobimane gave the 2'-S-alkylated product 33 in aqueous solution. Application of the phosphoramidite unit 22 to the solid phase synthesis using aminopropyl CPG gel gave successfully [U(2'-p)p](n)U (n = 1, 3, 5). It was found that stability of the succinate linker between the CPG and oligouridylates was unaffected by the treatment with DBU when BSA was present. Several enzymatic properties of the synthetic 2'-phosphorylated and 2'-thiophosphorylated oligouridylates are also described.
- Sekine,Tsuruoka,Iimura,Kusuoku,Wada,Furusawa
-
p. 4087 - 4100
(2007/10/03)
-
- MODERN FRIEDEL-CRAFTS CHEMISTRY. XIV. ON THE CYCLIZATION OF SELECTED ARYL HYDROXYALKYL SULFIDES
-
The feasibility of cycloalkylation reactions in the presence of Friedel-Crafts catalysts was demonstrated in a nimber of aryl hydroxyalkyl sulfides (1-5), and benzyl hydroxyalkyl sulfides (6-7).Treatment of compounds (1-7) with Friedel-Crafts catalysts gave diaryl disulfides, diaryl sulfides, arene thiols, chlorohydrins, aryl chloroalkyl sulfides, aryl alkenyl sulfides and cyclization products.It is noteworthy to mention that cyclization products were isolated only in cases where the hydroxyl group is linked to a tertiary carbon atom as in compounds 3 and 7.A suitable reaction pathway is suggested to rationalize the formation of the various reaction products.
- El-Khawaga, A. M.,El-Zohry, M. F.,Ismail, M. T.,Abdel-Wahab, A. A.,Khalaf, A. A.
-
p. 265 - 270
(2007/10/02)
-
- Solvomercuration-Demercuration. 9. Oxymercuration-Demercuration of Chloro-, Epoxy-, and Thiomethyl-Substituted Alkenes
-
The oxymercuration-demercuration (OM-DM) of allyl, crotyl, 3-buten-1-yl, 4-penten-1-yl, and 5-hexen-1-yl chlorides and methyl sulfides as well as 3,4-epoxy-1-butene, 4,5-epoxy-1-pentene, and 5,6-epoxy-1-hexene has been studied.Allyl chloride undergoes a slow but normal OM to give the Markovnikov oxymarcurial.However, in situ demercuration under the standard conditions (NaOH, NaBH4) gives only allyl alcohol.Fortunately, demercuration with an ethanolic solution of sodium borohydride results in high yields of the chlorohydrin accompanied by small amounts of propylene oxide.In contrast, crotyl chloride fails to give any products resulting from the OM-DM sequence.Thus, 3-buten-2-yl chloride underwent only solvolytic reaction while 2-methylallyl chloride underwent exclusive OM to give, upon DM, the expected Markovnikov chlorohydrin.Similarly, 3-buten-1-yl chloride underwent exclusive hydration under the standard OM-DM conditions.In the case of 4-penten-1-yl chloride, the C1-C5 neighboring-group participation was seen during OM.However, 5-hexen-1-yl chloride showed exclusive hydration to give a 94percent yield of the Markovnikov chlorohydrin.The approximate rates of solvolysis of a series of representative alkyl halides have been determined under the OM conditions.The OM-DM of 3,4-epoxy-1-butene proceeded to give hydrated products although the yield was low, ca. 60percent.On the other hand, 4,5-epoxy-2-pentene gave products arising only from participation of the epoxide ring in the OM stage.Moreover, the yields of these products are very low, only ca. 15percent.By contrast, the OM-DM of 4,5-epoxy-1-pentene proceeds cleanly, giving a 96percent yield of the Markovnikov epoxy alcohol.In the case of 5,6-epoxy-1-hexene, ca. 80percent of the products arise from epoxide participation in the OM stage.With the exception of the crotyl derivative, the (methylthio)alkenes undergo hydration cleanly, although slowly, to give approximately 70-80percent yields of the thio alcohols.The crotyl alkene gave 3-butene-2-ol in only ca. 20percent yield.
- Brown, Herbert C.,Lynch, Gary J.
-
p. 930 - 939
(2007/10/02)
-
