Aryl nonaflates

To our delight we found that palladium-catalyzed cross-couplings between sulfoximines and aryl halides (or aryl nonaflates) work very well, affording N-arylated products in high yield [45]. Generally, Buchwald s Pd(OAc)2/BlNAP catalyst system (with CS2CO3 and toluene at 100 °C) was applied, and thereby a variety of N-aryl sulfoximines 58 - including enantiopure ones - were prepared (Scheme 2.1.1.17). 

As another alternative to triflates, aryl nonaflates (ONf) are easily prepared from phenol and commerically available perfluorobutane sulfonyl fluoride 243, and used for Pd-catalysed coupling with halides [111]. Aryl nonaflates are more reactive than aryl triflates. / -Iodophcnyl nonaflate (244) gives 245 by chemoselective reaction of the... 

Hartwig has reported a DPPF/Pd-catalyzed C-N coupling reaction between a diarylamine and an aryl nonaflate, Eq. (63) [64bj. The coupling below proceeded in 95 -100% yield (NMR) and was used in a strategy to prepare oligo(m-aniline) compounds. 

Deoxygenation of phenols,l Aryl nonaflates, readily available by reaction of phenols with this reagent and triethylamine, undergo hydrogenolysis (H2, Pd/C) more rapidly and in higher yield (80-90%) than do aryl mesylates or tosylates. 

Reaction of diarylamines with aryl nonaflates as part of the synthesis of discrete oligomeric triarylamines has also been reported104. Only one paper reports the palladium-catalyzed reactions of diarylamines with aryl tosylates this reaction was conducted with X-phos 31 (Figure 8) as the ligand in mixed solvents of 5 1 toluene t-butanol98. 

Boisnard, S., Chastanet, J. and Zhu, J. (1999) A high throughput synthesis of aryl triflate and aryl nonaflate promoted by a polymer supported base (PTBD). Tetrahedron Letters, 40, 7469-lAll. 

Aqueous aminations with palladium catalysts that are not soluble in water have recently been described by Buchwald et al. [4]. The use of 2/Pd2dba3 and KOH in water without co-solvent gives excellent results in the amination of aryl chlorides containing nitro, trifluoromethyl, or pyridyl groups. Indoles and hindered aryl nonaflates can be aminated in good yields. In summary, co-solvents and phase-transfer catalysts are not necessary. 

Imamoto reported that Pd-catalyzed coupling of phosphine-borane with aryl halides is useful for preparation of asymmetric phosphines. Phosphines can be easily isolated from phosphine-boranes by exchange reaction with amines such as pyrrolidine and DABCO [10]. Lipshutz found that aryl nonaflates ( Nf = nonafluorobutanesulfonate) and triflates are good substrates for coupling with BHs-stabilized diaryIphosphines. Selective coupling with nonaflate without... 

Most recently, aryl fluoroalkanesulfonates [Ar0S02(CF2) CF3] have been proposed as an alternative to triflates, because they are easily prepared using commercially available fluoroalkanesulfonic anhydrides or halides. Aryl nonaflates are especially useful, being readily prepared and stable to flush column chromatography (Scheme 19). " ... 

Recently, Buchwald reported the coupling of aryl nonaflates [154] with soluble bases under microwave irradiation. With a catalytic system comprising Pd2(dba)3, and either XantPhos, X-Phos or an X-Phos derivative as ligand, Buchwald efficiently coupled electron-rich and electron-neutral aryl nonaflates in the presence of DBU or MTBD as base, even when bearing functional groups, such as carbonyl-containing groups [155]. 

Zinc amide 59 shows better chemoselectivity (but lower reactivity) and leads to the formation of aryl- and heteroarylzinc chlorides. Notably, it can be used to achieve [82] directed ortho- and meta-zincation of functionalized aryl nonaflates, thus providing suitable substrates for further Negishi cross-coupling reactions. 

Polymethylhydrosiloxane (PMHS) made hypercoordinate by KF is responsible for the regeneration of the tin hydride. These conditions were successfully applied to the C(sp >-C(sp ) carbon-carbon bond formation involving aryl iodides, alkenyl halides (bromide or iodide) or benzyl bromide. Aryl nonaflate and allyl bromide proved to be ineffective partners under these conditions. 

Recently, a MW-promoted procedure for one-pot, two-step conversion of aryl alcohols to aryl fluorides via aryl nonafluorobutylsulfonates (ArONf) was reported (Scheme 44). Moderate to good yields were achieved by this MW-assisted palladium-catalyzed fluorination sequence. The in situ conversion of aryl alcohols to aryl nonaflates using CsF as base, followed by the MW heated (180 °C) fluorination, catalyzed by [Pd2(dba)3] (dba= dibenzyhdeneacetone) andt-BuBrettPhos [2-(di-ter<-butylphosphino)-2, 4 6 -triisopropyl-3,6-dimethoxy-l,T-biphenyl], allowed full conversion after 30—60 min reaction. ... 

Wannberg J, Wallinder C, Unliisoy M, Skold C, Larhed MJ. One-pot, two-step, microwave-assisted palladium-catalyzed conversion of aryl alcohols to aryl fluorides via aryl nonaflates. Org Chem. 2013 78 4184- 189. 

Very recently, Barluenga and coworkers have reported that aryl nonaflates can be employed in the coupling with tosylhydrazones under the catalytic system Pd2(dba)3-Xphos-LiO Bu, with an additional 5 equiv. of H2O in dioxane (Fig. 23) [94]. Halide salt has been commonly utilized to accelerate the Pd-catalyzed coupling reaction of aryl sulfonates [100, 101]. This is also the case for the coupling reaction... 

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