Hypervalent iodonium salts

In 1986, Tamura et al. found that intra- and intermolecular sp -sp C-H couplings of aromatic compounds (Ar-H) and a-acylsulfides could be 

Entry Additive Solvent Temperature/°C Time/h Yield% 28 29  

The substrate scope, the optimum reaction conditions and the presumed reaction pathway in a series of intramolecular couplings of phenyl ether derivatives have been well investigated by Kita et al. In the reaction of norbelladine derivative 27, which has 4-methoxyphenyl and 3,4-dimetho)y-phenyl groups, normal atyl-aryl C-C coupling products (28) are exclusively 

PIFA (0.125 equiv.) mCPBA (0.75 equiv.) BF3 EtaO (1 equiv.) 

6-dimethylphenol by PIDA followed by homocoupling giving diphenoqui-none 33 and subsequent reduction by the excess starting material (SM). 

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Furthermore, arylthiophenes have been prepared using the Stille coupling of hypervalent iodonium salts [96] or organolead compounds [97, 98] as electrophiles in place of aryl or vinyl halides and triflates. Hypervalent iodonium salts are sufficiently reactive to undergo coupling at room temperature. 

Palladium-catalysed cross-coupling of organotellurium compounds with hypervalent iodonium salts... 

It was reported that Pd(0)-catalyzed coupling reactions of allenic alcohols, amines and acids with hypervalent iodonium salts afforded cyclized heterocyclic tetrahydrofurans, tetrahydropyrans, pyrrolidines, piperidines, or lactones under mild conditions <99SL324>. Intramolecular 1,5-hydrogen atom transfer radical cyclization reaction of pyrrolidine derivatives was examined. Reaction of 3,4-dialiyloxy-JV-(0-bromobenzyl)pyrtolidine gave hexahydro-... 

A polyethylene glycol-polystyrene graft copolymer palladium catalyst has been used in allylic substitution reactions of allyl acetates with various nucleophiles in aqueous media.58 Another polymer-bound palladium catalyst 40 was developed and used in a Heck coupling of allylic alcohols with hypervalent iodonium salts to afford the substituted allylic alcohols as the sole products under mild conditions with high catalytic efficiency.59 The same polymer-bound palladium catalyst has also been used for Suzuki cross-coupling reactions.60... 

Jang, S. B. Polymer-Bound Palladium-Catalyzed Coupling of Allylic Alcohols with Hypervalent Iodonium Salts, Tetrahedron Lett. 1997, 38, 4421. 

Kang, S.-K., Lee, S.-H., Lee, D. Copper-catalyzed N-arylation of amines with hypervalent iodonium salts. Synlett 2000, 1022-1024. 

Kang et al. showed that under the catalysis of Pd(PPh3)4 (5 mol%) the reactions of 4,5- or 5,6-allenyl alcohols/toluenesulfonamides and 4,5- or 5,6-allenoic acids with hypervalent iodonium salts led to the formation of five- or six-mem-bered-ring heterocyclic products (Schemes 22 and 23) [15, 16]. With AT-(3,4-pentadienyl)toluenesulfonamide, a mixture of four- and six-membered-ring products was also formed. 

Jeffery has reported an alternative additive-based solution to yield Hy-abstracted products. Mizoroki-Heck reaction of allylic alcohols with aryl or alkenyl hahdes in the presence of silver salts (AgOAc or Ag2C03) results in selective Hy -abstraction [7]. Similar hydroxy-coordination to the cationic organopalladium intermediates are believed to be involved in this system. In this regard, the use of hypervalent iodonium salts is also effective for generating cationic palladium species [8]. 

Kurihara, Y, Sodeoka, M. and Shibasaki, M. (1994) A novel and efficient coupling reaction of sodium tetraphenylborate with hypervalent iodonium salts. Chem. Pharm. Bull., 42, 2357-60. 

In addition to palladium catalysts, nickel—as a less expensive catalyst—was also explored in the caibonylative coupling of organostannanes with hypervalent iodonium salts [74]. In the presence of Ni(acac)2 (10 mol%) in NMP at 70 °C, organostannanes and hypervalent iodonium salts were caibonylative coupled and gave the corresponding ketones in good yields (Scheme 4.37). 

Additionally, copper was used as a powerful catalyst in the carbonylative coupling of hypervalent iodonium salts with organostannanes and organoboranes as well [75]. In the presence catalytic amount of Cul, ketones were produced in good yields from their parent molecules under mild conditions (Scheme 4.38). 

Moreover, manganese chloride as a catalyst for carbonylative coupling of organostannanes and hypervalent iodonium salts was developed by Kang and... 

Hypervalent iodonium salts (RI+PhX ) selectively transfer the R group (phenyl, p-anisyl, 2-thienyl, ( )-/3-styryl) and couple with R of R SnBus to furnish unsymmetri-cal ketones in excellent yields under very mild reaction conditions within a short period of time (1 atom of CO, 0.2% of PdCl2, 25 °C, 20 min) (Scheme 11). The reaction is most successfully performed in an aqueous medium (DME/H2O, 4 1). In dry DME, the reaction does not give clean products. 

Alkenylation/Arylation. The palladium-catalyzed coupling of TMSOF with hypervalent iodonium salts under mild aqueous conditions provides a route to /-substituted 3,/-unsaturated butyrolactones in excellent yield (eq 21). ... 

Lu C, VanDerveer D, DesMarteau DD (2008) Fluoroalkylation of imidazoles by hypervalent iodonium salts. Org Lett 10 5565-5568... 

Pd(0)-catalyzed arylation of the aryl-substituted a-allenic alcohols with hypervalent iodonium salts afforded substituted trans-epoxides. Alternatively, arylation of the alkyl-substituted a-allenic alcohols in the presence of K2CO3 afforded syn-diol cyclic carbonates and trans-epoxides in the presence of CS2CO3 (Scheme 5). 

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