1Abstract: The preparation of diverse β -iodo ethers and iodohydrins is efficiently achieved in mild conditions by reaction of alkenes with two equivalents of I 2 and alcohols (EtOH, i -PrOH, tBuOH) or water, respectively. β -Iodo ethers are useful intermediates for stereoselective radical reactions 1 and for the synthesis of E or Z alkenes with good to moderate diastereoselectivity. 2 Traditional methods for preparing these compounds are the reaction of alkenes with N -iodosuccinimide/alcohols 3 or I 2 /alcohols and a metal salt, such as Cu(II), 4 Ag(I) 1 and Ce(IV). 5 Although Rutledge and co-workers 6 reported a method of synthesis of iodohydrins ( β -iodo alcohols) by reaction of alkenes with 2.4 equivalents of iodine in a biphasic system (water, chloroform, and sulfolane) as well as a similar route to β -iodo ethers with alkenes, iodine, sulfolane and an alcohol, this system is somewhat complicated due to the possibility of the sulfone participating in the reaction, 6 prolonged reaction times (24-25 h), and more complex experimental procedures (such as anhydrous solvents).In previous work we studied an easy route for the preparation of iodohydrins from alkenes by reaction with iodine and water in the presence of diverse metal salts, and showed that the readily available and inexpensive Fe 2 (SO 4 ) 3 gave the best yields. 7a This methodology does not require special techniques and we decided to extend it to the reaction of alkenes with iodine/Fe 2 (SO 4 ) 3 in the presence of alcohols as a possible route to β -iodo ethers.Applying our methodology we obtained 1-ethoxy-2-iodo-1-phenylethane (1a) in 63% isolated yield by the reaction of styrene with I 2 , Fe 2 (SO 4 ) 3 and ethanol (solvent) at room temperature. Surprisingly, when a second equivalent of iodine was used in place of the ferric salt, we obtained the same product 1a in a shorter reaction time (2.5 h) and slight higher isolated yield (75%). This was unexpected, since according to the literature information the metal salt was supposed to be necessary in order to obtain good yields and avoid the formation of 1,2-diiodoalkanes as undesirable side products. 4a In our hands, no diiodo compound was detected by the analytical procedures employed [HRGC (high resolution GC), 1 H NMR and 13 C NMR] and although we have used ethanol without further purification, no iodohydrin arising from small amounts of water in the solvent was detected either.Based on the above results, we decided to investigate the preparation of diverse β -iodo ethers using alkenes, alcohols and 2 equivalents of I 2 and the results are shown for Dedicated to Prof. W. Bruce Kover on the occasion of his 60th birthday the formation of 1a-g in Table 1. In all the reactions the purity of the isolated products (>95%) was confirmed by 1 H NMR, 13 C NMR, FT-IR and HRGC and the yields of the β -iodo ethers were good to moderate even with secondary and tertiary alcohols. Only in the case of hex-1-ene did the reaction give predominantly the secondary ether mixed with some of its regioisomer (85:15 by...

No abstract

No abstract

Epóxidos podem ser preparados eficientemente a partir da reação de alquenos com ácido tricloroisocianúrico em acetona aquosa seguido de tratamento da cloroidrina resultante com KOH aquoso em éter / pentano.The preparation of epoxides is efficiently achieved in mild conditions by reaction of alkenes with trichloroisocyanuric acid in aqueous acetone followed by treatment of the resulting chlorohydrin with aqueous KOH in ether / pentane.

A reação de diversos alquenos com 0,4 equiv. mol de PBr 3 /SiO 2 em diclorometano à temperatura ambiente forneceu os brometos de alquila com regiospecificidade Markovnikov em 50 -100% de rendimento e tempos curtos de reação. O isopreno a -8 o C nestas mesmas condições forneceu somente o 1-bromo-3-metil-2-buteno em 54%The reaction of several alkenes with 0.4 mol equiv. PBr 3 /SiO 2 in dichloromethane at room temperature gave the alkyl bromides with Markovnikov regiospecificity in 50 -100% yield and short reaction time. Isoprene at -8 o C in these conditions gave 1-bromo-3-methyl-2-butene only (54%).