Iodination reagents alkenes

Under certain conditions, amides can add directly to alkenes to form N-alkylated amides. 3-Pentenamide was cyclized to 5-methyl-2-pyrrolidinone by treatment with trifluorosulfonic acid. Acylbydrazine derivatives also cyclized in the presence of hypervalent iodine reagents to give lactams. When a carbamate was treated with Bu3SnH, and AIBN, addition to an alkene led to a bicyclic lactam. 

Iodination reagents combined with aryl phosphines and imidazole can also effect reductive conversion of diols to alkenes. One such combination is 2,4,5-triiodoimidazole, imidazole, and ttiphenylphosphine.297 These reagent combinations... 

Iodination reagents combined with aryl phosphines and imidazole can also effect reductive conversion of diols to alkenes. One such combination is 2,4,5-triiodoimidazole, imidazole, and triphenylphosphine.215 These reagent combinations are believed to give oxyphosphonium intermediates which then serve as leaving groups, forming triphenylphosphine oxide as in the Mitsunobu reaction (see Section 3.2.4). The iodide serves as both a... 

Only the head-to-tail adducts were obtained in the [2+2] photoaddition of 4-hydroxy-l-phenyl[l,8]naphthyridin-2(l//)-one with various alkenes in methanol (Scheme 3). The photolysis of the hypoiodites generated by the in situ reaction of the cycloadducts with excess mercury(ll) oxide-iodine reagent in benzene induced a regioselective scission of the non-ring junction bond of the alkoxyl radical to give substituted 3,9-dihydro-9-phenylyfuro[2,3- ][l,8]naphthyridin-4(2//)-one and/or 3,5-dihydro-5-phenylfuro[3,2-f][l,8]naphthyridin-4-(2//)-ones <1996T6125>. 

Alkenyl(phenyl)iodonium salts have attracted a significant interest recently as stable and readily available powerful alkenylating reagents. Several convenient, general procedures for the stereoselective synthesis of alkenyliodonium salts from silylated or stannylated alkenes and the appropriate hypervalent iodine reagents are known [5]. The chemistry of alkenyliodonium salts has been extensively covered in several recent reviews [42 - 45]. 

Bis(arylsulfanyl)alkenes 30 can be prepared from alk-l-ynes and a hypervalent iodine reagent 29, prepared from (diacetoxyiodo)benzene (27) and 2,3,5,6-ielrafluorobenzenethiol (28) in pyridine. ... 

As for many other nucleophiles, the nitrite anion undergoes addition to the iodonium ion generated by the reaction of alkenes and 1,3-alkadienes with electrophilic iodine reagents. Two procedures have been described bis(pyridine)iodine(I) tetrafluoroborate136,137 [prepared from mcrcury(II) oxide and tctrafluoroboric acid supported on silica gel and pyridine on dichloromethane] and copper(II) tetrafluoroborate [prepared from copper(II) oxide and te-trafluoroboric acid] and iodine138 139. trans Addition would be expected for all products from mechanistic considerations, however, only the cyclohexene adduct 1 has been shown to have trans configuration ( H-NMR spectroscopy)139. 

Wc-Ditosylates are formed from alkenes on reaction with the hypervalent iodine reagent 50. Enantioselectivity is moderate. 

Dichloroiodo)benzene can be convenientiy generated in situ from other hypervalent iodine reagents and used for subsequent chlorination of organic substrates. In a specific example, an efficient chlorination of p-keto esters, 1,3-diketones and alkenes has been performed using iodosylbenzene with concentrated HCl, selectively giving a-chloro-p-keto esters, 2-chloro-l,3-diketones and 1,2-dichloroalkanes, respectively [63]. A stereoselective anti-addition was observed in the chlorination of indene under these conditions. 

Bortolini, O., Bottai, M., Chiappe, C., Conte, V and Pieraccini, D., Trihalide-based ionic liquids. Reagent-solvents for stereoselective iodination of alkenes and alkynes. Green Chem. 4, 621-627 (2002). 

In addition, Trauner and co-workers recently presented the short total synthesis of racemic merochlorin B by means of this biomimetic [3+2] cationic condensation between phenol ring carbons and the internal nucleophilic alkene moiety mediated by hypervalent iodine reagents (Scheme 20) [107]. 

This review is devoted to an overview of phenol dearomatization and its application in natural product synthesis through the use of a special class of phenolophile reagents that has attracted much attention in recent years, the hypervalent iodine reagents. These polyvalent iodine compounds, also called iodanes, are oxidizing electrophiles that can mediate a wide number of diverse chemical transformations not only of (hetero)aromatic compounds, but also of inter alia alkenes, alkynes, alcohols, sulfides, amines and amides, (enolizable) carbonyl... 

In contrast, Muniz reported an indole synthesis from 2-vinyl anilines 13, which relies on activation of the alkene moiety by the hypervalent iodine reagent [9]. The reaction employs a sterically congested Koser reagent generated in situ from iodosobenzene and the bulky sulfonic acid 15. The reaction provides synthetically unique access to 2,3-unsubstituted indoles 14 and can also be conducted under catalytic conditions. 

To date, this chemistry remains rather unexplored with respect to the development of related transition metal catalyses [43]. Still, difunctimialization of alkenes with hypervalent iodine reagents has been explored extensively over the past few decades [44], and there are important recent contributions that indicate that hypervalent iodines can indeed serve as suitable chiral reagents or catalysts for enantio-selective oxidation of alkenes [43-46]. 

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