Sulfonamides hydroamination with

Ph3PAuOTf has been shown to catalyse intra- and inter-molecular hydroamination of unactivated alkenes with sulfonamides in a Markovnikov fashion.115 The same complex catalyses hydroamination of 1,3-dienes with carbamates (e.g. PhCH2OCONH2) and sulfonamides at room temperature.116 An intramolecular version of the hydroamination with the Cbz group (benzyloxycarbonyl) has also been reported. The latter... 

Krause has shown that gold(III) salts catalyze the intramolecular emJo-hydroamina-tion of N-protected a-aminoallenes [35]. For example, treatment of the diasteromeri-cally pure a-allenyl sulfonamide 44 with a catalytic amount of AUCI3 in dichlor-omethane at 0 °C for 1 h formed the pyrroline derivative 45 in 95% yield with 96% diastereomeric purity (Scheme 11.6). The protocol tolerated aryl and alkyl substitution of the distal allenyl carbon atom and was also effective for the hydroamination of N-unprotected a-allenylamines although these latter transformations required considerably longer reaction time. In a similar manner, Lee has reported the gold (Ill)-catalyzed ewdo-hydroamination of 4-allenyl-2-azetidinone 46 to form bicydic P-lactams 47 (Eq. (11.25)) [36]. 

Toste has described the intramolecular enantioselective hydroamination of y- and 6-aUenyl sulfonamides catalyzed by enantiomerically pure bis(gold) phosphine complexes [42]. For example, treatment of the terminally-disubstituted y-allenyl sulfonamide 59 with a catalytic amount of [(R)-3,5-xylyl-binap](AuOPNB)2 (OPNB =p-nitrobenzoate) formed protected pyrrolidine 60 in 88% yield with 98% ee (Eq. (11.34)). Likewise, treatment of 6-allenyl sulfonamide 61 with a catalytic amount of [(JJ)-Cl-MeObiphep](AuOPNB)2 in nitromethane at 50 °C for 24h formed 2-alkenyl piperidine 62 in 70% isolated yield with 98% ee (Eq. (11.35)). Realization of high enantioselectivity in this protocol required employment of both a terminally disubstituted allene and a sulfonamide nucleophile. 

Mild and selective 1 1 reactions of amines with 1,3-dienes without telomer-ization are still limited. The recently reported bismuth-catalyzed intermolecular hydroamination with various amides (carbamates, sulfonamides, and carboxamides) to produce allylic amines in good yields is a good example of such a reaction (Equation 56 and Scheme 11.4) [80]. Some additives are necessary to optimize the reaction conditions. Cyclic and acyclic dienes were tested. The isomer ratio (1,2-adduct versus 1,4-adduct) depended on the nature of the dienes. 

Table 2 Bi(OTf)3/Cu(CH3CN)4PF6/dppe-catalyzed intermolecular hydroamination of la with various carbamates, sulfonamides, and carboxamides...

The enantioselective hydroaminations of allenes with chiral phosphine catalysts was accomplished with substrates that had a terminal symmetric substitution and with the amines protected as carbamates or sulfonamides. The same symmetric substituents were necessary for the enantioselective transformation nsing chiral counterions. However, very recently, high enantiomeric excesses were reached with trisubstituted asymmetric allenes by a dynamic kinetic enantioselective hydroamination of allenyl carbamates (eqnation 110), even thongh the E/Z ratio of the prodncts was not optimal. 

Hydroamination of olefins is also possible with gold catalysts. In this reaction, the attack comes Ifom a nitrogen nucleophile as a carbamate,a urea, an amide, or a sulfonamide. In the latter case, the reaction can be carried out intermolecularly. While the carbamates, ureas, and amides give only products of intramolecular anunations, the sulfonamides can perform the intermolecular addition. Only the addition of ureas (equation 146) takes place at room temperature, and in the rest of the additions heating is required. The catalysts of choice in all these reactions are cationic gold(I)-species stabilized by phosphines or NHC ligands. The reaction times have been reduced by the use of microwave irradiation. The mechanism of the hydroamination reaction has been studied in detail theoretically. ... 

The intermolecular addition of carbamates to 1,3-dienes (equation 147) under mild conditions has been described as well. The hydrothiolation of 1,3-dienes has also been reported. " Other related conjugate additions can be performed over methylenecyclopropanes (equation 148) with sulfonamides and the resulting product cyclizes by a second hydroamination of an olefin, finally yielding cyclic sulfonamides. This behavior is reproduced in a similar reaction for the ring opening of vinylcyclopropanes with sulfonamides. One more example in this group of reactions is the synthesis of dUiydrobenzofurans from aryl-allyl ethers. ... 

Doye s group [81] showed that a dinuclear titanium-sulfonamidate complex (Scheme 21), with a tetrahedral sulfur in the ligand backbone, can be used for intermo-lecular hydroaminoalkylation as well. This system gives mixtures of branched and linear products, although to date there has been no mechanistic rationale provided for the reduced regioselectivity of group 4 metal complexes in this transformation. There has been one report by Zi s group [44] that describes axially chiral bis(sulfonamidate) tantalum and niobium complexes for application as precatalysts for hydroamination and hydroaminoalkylation. Unfortunately, these complexes did not show any reactivity for either of these reactions. 

Hydroamination. Sulfonamides and weakly basic anilines add to alkenes with yields >95%, when catalyzed by (cod)Pt(OTf)2. Interestingly, (cod)RhBF4 [also with DPPB ligand] induces intramolecular hydroamination in the anti-Markovnikov fashion ... 

The distal bond cleavage occurs in hydroamination. Reaction of MCP 208 with dibenzylamine afforded the allylic amine 209 by using the combination of 7r-allylpalladium chloride with DPPP as a catalyst [61]. Similarly sulfonamide 211 was allylated with MCP 210 to produce the diallylated amide 212 using a complex mixture of Pd(0), Pd(II), and PPhs as a catalyst [62]. The use of Pd(0)-PPh3 in an appropriate ratio seems to be effective. 

An intramolecular gold-catalyzed hydroamination took place upon heating of cyclic dienes bearing a sulfonamide side chain with PhsPAuCl and AgOTf. In this case, 1,4-addition of the amide leads to the formation of hexahydroindoles and related heterocycles. The presence of the bulky phenyl groups in the tether is crucial for... 

Stereochemical and kinetic analyses of the Brpnsted acid-catalysed intramolecular hydroamination/deuterioamination of the electronically non-activated cyclic alkene (13) with a neighbouring sulfonamide nucleophile have been found to proceed as an anh-addition (>90%) across the C=C bond to produce (15). No loss of the label was observed by and NMR (nuclear magnetic resonance) spectroscopies and mass spectrometry (MS). The reaction follows the second-order kinetic law rate = 2 [TfOH] [13] with the activation parameters being = 9.1 0.5 kcal moP and = -35 5 cal moP An inverse a-secondary kinetic isotope effect of d/ h = (1-15 0.03), observed for (13) deuteration at C(2), indicates a partial CN bond formation in the transition state (14). The results are consistent with a mechanism involving concerted, intermolecular proton transfer from an N-protonated sulfonamide to the alkenyl C(3) position coupled with an intramolecular anti-addition by the sulfonamide group. ... 

Yamamoto has reported the intramolecular e%o-hydroamination of N-allenyl sulfonamides and carbamates catalyzed by simple, unligated gold(I) and gold(III) salts. Noteworthy was that cyclization of N-allenyl sulfonamide derivatives that possessed an axially chiral allenyl moiety occurred with highly selective transfer of chirality to the newly formed tetrahedral stereogenic carbon atom [38]. For example, treatment of enantiomerically enriched y-allenyl tosylamide 52 (96% ee) with a catalytic amount of AuCl in THF at room temperature led to isolation of ( )-2-(l-heptenyl)pyrroldine ( )-53 in 99% yield with 94% ee (Eq. (11.28)). 

In contrast to the hydroamination of alkenes with sulfonamides, the potential of an acid-catalyzed reaction pathway in the hydroamination of alkenes with carboxamide derivatives appears less likely. Hartwig found that the intramolecular hydroamination of alkenes with N-arylcarboxamides was only realized in the presence of stoichiometric amounts of triflic add [50]. In contrast, He reported that triflic add catalyzes the intramolecular hydroamination of an N-4-methyl-4-pentenyl carbamate in toluene at 85 °C [55]. However, in the corresponding gold(I)-catalyzed transformation, the intramolecular hydroamination of an N-4-methyl-4-pentenyl carbamate was markedly slower than was the intramolecular hydroamination of an N-4-pentenyl carbamate [52], which is inconsistent with the antidpated behavior of an acid-catalyzed pathway. Furthermore, control experiments firmly ruled out the presence of an acid-catalyzed reaction pathway in the gold(I)-catalyzed intramolecular hydroamination of alkenes with carboxamide derivates and ureas [53, 54]. 

Tunge [261] showed that Pd(0) catalysts can be used for the hydroamination of vinyl ethers with sulfonamides (Scheme 15.61). Most recently, Hartwig [262] has shown that Ir(I) catalysts in combination with amides and sulfonamides can be used for intermolecular hydroamination, including the highly challenging... 

Scheme 15.62 Ir-catalyzed hydroamination of unactivated alkene with amides and sulfonamides.

The success of simple Au(I) PPhj systems for catalysis inspired the development of less strongly donating phosphine hgands in order to enhance it-acidity to improve reactivity with protected amines. Using triphenyl phosphite as a hgand, intermolecular hydroamination of alkenes with sulfonamides can be accomphshed with low catalyst loadings (Scheme 15.63) [263]. 

Scheme 15.63 Au-catalyzed hydroamination of alkenes and 1,3-dienes with sulfonamides.

Iridium The intermolecular hydroamination of unactivated C=C bonds in ct-olefins (RCH=CH2) and bicycloalkenes (norbornene and norbornadiene) with arylamides (ArCONH2) and sulfonamides has been attained upon catalysis by chiral iridium complexes (PP)IrHCl(NHCOAr)(NH2COAr) [PP = chiral bidentate diphosphine]. Mechanistic studies identified the product of N-H bond oxidative addition and coordination of the amide as the resting state of the catalyst. Rapid, reversible dissociation of the amide precedes reaction with the alkene, but an intramolecular, kinetically significant rearrangement of the species occurs before the reaction with alkene. ... 

Zirconium Intermolecular hydroamination of both terminal and internal alkynes R C=CR with primary amines R NH2 to produce (after subsequent reduction) saturated secondary amines RiCH2-CH(NHR )R can be attained with the in situ generated zirconium catalysts (Me2N)4Zr (5 mol%) and sulfonamide (10 mol%). " Zirconium-catalysed intramolecular hydroamination (225) (226) has been studied theoretically " as for the analogous iridium-catalysed cyclization of (177) discussed (g) earlier " and similar conclusions have been reached regarding the hydrogen bonding, and so on. 

Although hydroamination of allenes can be easily achieved with group 4 and group 5 metal catalysts, the stereoselectivity of these systems is rather limited. Several attempts to perform asymmetric hydroamination/cyclization of aminoallenes employing chiral aminoalcohols [260, 261] and sulfonamide alcohols [262] as chiral proligands for titanium- and tantalum-based catalyst systems have produced vinyl pyrrolidines with low selectivities only. While the titanium catalysts were... 

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