2-Iodo 1-sulfonamide

SESCl in Synthesis. The SES group has been used successfully in the synthesis of glycosides (eq 5). Reaction of (6) with SES-sulfonamide and iodonium di-sym-collidine perchlorate provides the iodo sulfonamide (7) in 82% yield. Treatment of (7) with (benzyloxy)trihutylstannane in the presence of silver(I) tri-fluoromethanesulfonate provides the /3-benzyl glycoside (8). Ru-oride treatment of (8) removes both the silyl ether and the SES group, giving the amino alcohol (9). 

Compound 152 was destined to house the lactose bearing the ceramide unit and was therefore converted to triol 155. While 155 has several potential glycosylation sites, in principle, the C3 hydroxyl is the most reactive position. A suitable donor could be fashioned by subjecting 153, the core of the Le sector, to IDCP iodo-sulfonamidation (see 156). Addition of ethanethiolate effected the roll over reaction and the donor was ready for coupling with 155. In the event, treatment of 157 with 155 under promotion of MeOTf did, in fact, give the desired tetrasaccharide 158, albeit often in low yield (35-55%). In addition, the reaction mixture appeared to contain significant quantities of at least one regioisomer. 

It was known from solution-based studies that an iodonium electrophile adds to the glycal linkage, in the presence of a sulfonamide, in a transdiaxial fashion.24 This results in formation of a 1 -a-sulfonamido-2-p-iodo product. Furthermore, displacement of iodine can be induced by nucleophilic attack of a thiolate nucleophile... 

Scheme 50 Allylation of a-iodo lactones Al-BINOL and Al-sulfonamide ligands as single...

Oxidative C-H amination has been an area of intensive research since the publication of CHEC-II(1996). This methodology has been applied to the synthesis of a variety of 1,2-thiazine 1,1-dioxides. In the simple cases, substrates containing an aromatic C-H can be cyclized in the presence of hypervalent iodine. For instance, the reaction of A-methoxy(2-arylethane)sulfonamide 202 with [hydroxyl(tosyloxy)iodo]benzene rapidly affords benzenesulfon-amide 203 in excellent yield (Equation 30) <20030BC1342> see also <2000JOC926> and <2000JOC8391>. 

Palladiun-catalyzed two component cascade cyclization of 1-iodo-vinylbenzenes 489 and sulfonamide 490 gave 6-substituted 2-tosyl-ll-methylene-2,3,4,6,11,1 la-hexahydro-lH-pyrazino[l,2-b]isoquinolines 491 (07T6152). 

More recently, the effect of substituents in the arenesulfonyl moiety on Cu(I)-catalyzed aziridinations of cyclohexene with a series of [(arenesulfonyl-imino)iodo]benzenes was evaluated (Scheme 65) [177]. Iminoiodanes possessing p-OMe,p-CF3, andp-N02 substituents gave higher yields of aziridines than the tosylimino analog. Product yields in these reactions are not simply related to relative rates of aziridination (p-MeO >p-Me >p-N02), and appear to reflect partitioning of the copper(III)-nitrene intermediates between aziridination of the C,C-double bond and reduction to the corresponding sulfonamides. 

Although the foregoing studies are focused on imidations of P, S, Se, and As compounds with [(tosylimino)iodo]benzene, and related reactions, PhI = NTs has also been utilized for conversions of trialkylboranes to N-alkyl-p-toluene -sulfonamides (Scheme 21) [47]. Such reactions presumably occur through N-tosylaminoborane intermediates (i.e., B-N bond formation). 

An interesting approach to 2,5-disubstituted 4-iodo-2,3-dihydropyrroles (8) has been reported, based on the cyclization of the sulfonamides 9 with iodine in the presence of potassium carbonate. The products could be dehydrogenated in good yields giving the corresponding pyrroles 10 with 2 equiv. of DBU at room temperature, while the use of only one equiv. of the base at elevated temperature led to partial loss of the iodine atom . 

Cyclization with PSHTIB ([hydroxyl(tosyloxy)iodo]arenes of sulfonamides bearing an electron-rich aromatic ring provides the corresponding spirosultam 423 <2003ARK11, 20030BC1342>. When the cyclization was applied to Wmethoxy(phenyl)methanesulfonamide, 186 (X = CH, R =OMe, R = R = H) was obtained which could not be obtained with the radical reaction method. On the other hand, photochemical conditions applied to Wmethyl-3-(phenyl)propanesulfonamide afforded 1,3-propanesultam 236 (R = Me, R = Ph) <2000JOC926>. 

Other compounds under consideration include ammoniacal copper-fatty acids, isothiazolinones, benzothiazoles, sulfonamides, tetrachloroisophthalonitrile, salicylanilide derivatives, and 3-iodo-2-propynyl butylcarbamate (8-J3). 

Amino sugars. Glycals undergo addition with the iodonium perchlorate and 2-(trimethylsilyl)ethanesulfonamide to afford 2-iodo-l-sulfonamide adducts which are transformed into the protected aminoglycosides on alcoholysis. 

Heterocyclization. Formation of A-tosyl-2-iodomethylaziridine from A-tosyl-allylamine requires iodine and NaH, whereas Ij-LiAl(OBu ) mediates cyclization of allyl A-acylcarbamates." A route to 4-iodo-2,3-dihydropyrroles by iodine-induced cyclization of homopropargylic sulfonamides involves a 5-endo-dig cyclization. ... 

A mixture of THF and DMPU has been used as a solvent for Sml2 in various reactions such as cyclization of alkynyl halides [90,91], tandem iodo-enone cy-clization/samarium enolate aldol reaction [92], coupling of (3-silylacrylic esters [93], deprotection of arenesulfonamides [94] and pyridine-2-sulfonamides [95], radical ring-opening reactions of cyclopropyl ketones and the trapping of the resulting samarium(III) enolates by a variety of electrophiles [96] (Scheme 41). 

A modification of the Hofmann-Loffler-Freytag reaction that avoids the harshly acidic conditions described above has been developed. The A-iodo compound is generated by reaction with iodine and iodobenzene diacetate. Warming or irradiating the reaction mixture promotes the formation of the lutrogen-centred radical and hence subsequent remote hydrogen atom abstraction. The reaction is particularly effective with carboxylic amides, sulfonamides or phosphoramidates, as illustrated in the transannular cyclization to give the indolizidine 20 and in the formation of the bicyclic produet 21 (4.21,4.22). ... 

Iodo- and o-bromoanilines as well as the corresponding carboxamides and sulfonamides can undergo Pd-catalyzed o-alkenylation and o-alkynylation. The cross-coupling products thus formed can then undergo catalytic aminopalladation to give indole derivatives. A few representative procedures for the synthesis of indoles are shown in Scheme 53.[i45].[i46]... 

Motherwell s group developed an original approach to the synthesis of biaryls based on the intramolecular free-radical i so-substitution reaction. This includes the reaction of ortho-iodo (or bromo) phenols, A/-methylanilines or A -methylbenzamides with various arylsulfonyl chlorides to give the respective sulfonates XXX, A -methyl sulfonamides XXXI, or iV-acylsulfonamides XXXII. The latter are reacted with tri-n-butyltin hydride in the presence of azobisisobutyronitrile (AIBN) in refluxing benzene to produce spirocyclic intermediate XXXIII, which, upon extrusion of sulfur dioxide, afforded the ortho-hydroxy- XXXIV, methyamino- XXXV, or /V-methyl carboxamido-substituted biphenyls XXXVI in moderate to good 3delds [1-4], Scheme 1. 

When three molar equivalents of AgOAc were added to a previous protocol for the synthesis of a 4-iodo-2,3-dihydropyrrole derivative, the yield increased from 30% to 83%. In general, the addition of AgOAc gave reasonable yields (69-87%) for the synthesis of 4-iodo-2,3-dihydropyrroles from homopropargylic sulfonamides via a 5-endo-dig cyclization (eq 25). ... 

Professor Knight has also Tetrahedron Lett. 2007,48, 7906) established a route to poly-substituted pyrroles 10, by iodination of alkynyl sulfonamides such as 9. Similarly, Richard C. Larock of Iowa State University foimd J. Org. Chem. 2007, 72, 9643) that 1-Cl cyclized methoximes such as 11 to the corresponding iodo isoxazole 12, and Stephen L. Buchwald of MIT uncovered Organic Lett. 2007, 9, 5521) the cycUzation of an enamide such as 13... 

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