Iodonium collidine perchlorate

Scheme 5.1 Mechanism of thioglycoside activation (a) by thiophiles X1 such as /V-bromosuccinimicle (NBS), 11,12 methyl triflate,13 dimethyl(methylthio)sulfonium triflate (DMTST),14 phenylselenyl triflate (PhSeOTf),17,18 iV-iodosuccinimide/triflic acid (MS/TfOH),19 20 and iodonium di-sym-collidine perchlorate (IDCP)21 (b) by tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBPA,+)25 and (c) via anomeric sulfoxides.26 The stereochemical outcome of these glycosylations follows the same general trends as with many other glycosyl donor/promoter combinations (m-CPBA = mcta-chloroperbenzoic acid).

Scheme 5.7 (a) Mechanism of the w-pentenyl glycoside-based glycosylation method. Electrophiles commonly employed include iodonium di-sym-collidine perchlorate (IDCP) and A-iodosuccinimide/triethylsilyl triflate (NIS/Et3SiOTf) (b) Mechanism for the activation of NIS by EtsSiOTf.55... 

Iodine-copper(II) acetate, 267 Iodine-mercury(II) oxide, 267-268 Iodine monochloride, 268-269 Iodine-silver carboxylates, 268 Iodine-silver nitrate, 268 lodoamination, 265-266 Iodocarbamation, 264-265 Iodocarbonates, 263 2 Iodoestradiol, 267 2-Iodoestrone, 267 Iodoiactonization, 263-264 C,-Iodomethylcephalosporins, 273 Iodonium di-svm-collidine perchlorate, 269 19-Iodononadecanic acid, 488 Iodophenylbis(triphenylphosphine)palladium, 269... 

Lemieux and Thiem developed the iodine glycosylation.16 You need an I+-reagent e. g. Y-iodosuccinimide (l-iodo-2,5-pyrrolidinedione, NIS) (47) or I(coll)2 (iodonium di-.sym-collidine perchlorate) (48). The mechanism of this step with the bromine reagent of 48 was evaluated by Brown. 1... 

Bis(syfn-collidine)iodine(I) perchlorate (Iodonium di-sym-collidine) perchlorate, +I(C8H N)2 C104 (1), 10, 212-213. 

In analogy to this approach, the cyclization of unsaturated furanosides and pyranosides, performed with iodonium dicollidine perchlorate [I(collidine)2C104] in dichloromethane, allows ris-2,5-disubstituted tetrahydrofurans to be obtained in moderate yield and with good to high diastereoselection122 -124. 

The addition of A,V-dibromobenzencsulfonamidc to hexose-derived glycals afforded, after reduction of the N —Br bond of the initial adducts, a mixture of diastereomeric 2-bromo-l-phenylsulfonylamino derivatives913 b. In the case of tri-O-benzyl-D-glucal the diastereoselectiv-ity in favor of the diaxial adduct 7 was improved by the alternative procedure using iodonium di-.cyw-collidine perchlorate and benzenesulfonamide (see Section 7.2.6.1.4.). 

Abbreviations Ac acetyl AIBN azobisisobutyronitrile All allyl Bn benzyl Bz benzoyl ClAc chloroacetyl DAST diethylaminosulfur trifluoride DBU l,8-diazabicyclo[5.4.0]-undec-7-ene DDQ 2,3-dichloro-5,6-dicyano-/)-benzoquinone DMDO dimethyldioxirane DMTST dimethyl(methylthio)sulfonium trifluoromethanesulfonate Fmoc 9-fluorenyl-methoxycarbonyl HDTC hydrazine dithiocarboxylate IDCP iodonium di-collidine perchlorate Lev levulinoyl MBz 4-methylbenzoyl Me methyl MEK methyl ethyl ketone MP 4-methoxyphenyl NBS iV-bromosuccinimide NIS A-iodosuccinimide Pent n-pentenyl Pfp pentafluorophenyl Ph phenyl Phth phthaloyl Piv pivaloyl PMB 4-methoxybenzyl TBAF tetrabutylammonium fluoride TBDMS tcrt-butyldimethylsilyl TBDPS tert-butyldiphenylsilyl TCA trichloroacetyl TES triethylsilyl Tf trifluoromethanesulfonyl TMS trimethylsilyl Tol 4-methylphenyl Tr trityl Troc 2,2,2-trichloroethoxycarbonyl Ts tosyl. 

GLYCOSIDES Bromotrimethylsilane-Cobalt(II) bromide. Iodonium di-sym-collidine perchlorate. Mercury(II) nitrate. Silver imidazolate. Stannous chloride-Silver perchlorate. 

For safety reasons it is probably advisable to substitute their iodonium(collidine)2 perchlorate, which is a potential explosive, with the corresponding triflate, which is made in the same manner as the perchlorate)]. 

Various pathways for the electrophilic addition to a glycal followed by nucleophilic opening of the resulting halonium ion can account for the different product distributions obtained from these reactions [74]. Irreversible formation of the halonium ion and subsequent nucleophilic displacement leads to the (B-g/wco compound, while reversible formation of the halonium ion followed by slow nucleophilic trans diaxial opening leads to the a-manno compound. Common T sources used to synthesise a-manno species include V-iodosuccinimide (NIS), and iodonium di-iym-collidine perchlorate (IDCP). An iodonium source is particularly favoured over a bromonium source, as this more readily allows further subsequent functionalisation of the product often via radical chemistry. The yields of... 

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