Butyl triflate

Other Alkylation Experiments. In other experiments lithium and sodium were used in place of potassium. Biphenyl and anthracene were used in place of naphthalene. 1,2-Dimethoxyethane was used in place of tetrahydrofuran. Butyl chloride, butyl bromide, butyl mesylate, butyl triflate, methyl iodide, and octyl iodide were used in place of butyl iodide. The conditions used in these experiments were very similar to the conditions used in the procedures described in the previous paragraphs. The isolation procedure was modified in those cases where the ionic salt, e.g., sodium iodide, was soluble in tetrahydrofuran. In these instances the tetrahydrofuran-soluble product was washed with water to remove the salt prior to further study. 

Molybdenum.— The reaction of r/tr o-3,3-dimethyl[l,2- H2]butyl triflate with [MoC1(CO)s( i C5H5)] (Scheme 3) proceeds with inversion of configuration at... 

Preparation of 2-Fluoro-4-methylacetamlide, 166 Fluorination with A-ferf-Butyl-Al-fluorobenzenesulfonamide Preparation of 1-Fluoro-l-octene, 166 Fluorination with A-Fluoro-2,4,6-trimethylpyridinium Triflate Preparation of Diethyl Fluorophenylmalonate, 166 Fluorination with Xenon Difluoride... 

Abbreviations Aik, alkyl AN, acetonitrile Ar, aryl Bu, butyl cod, 1,5-cyclooctadiene Cp, cy-clopentadienyl Cp , pentamethylcyclopentadienyl Cy, cyclohexyl dppm, diphenylphosphinome-thane dpme, Ph2PC2H4PMe2 Et, ethyl fod, 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octane-dionate HOMO, highest occupied molecular orbital LUMO, lowest unoccupied molecular orbital Me, methyl MO, molecular orbital nbd, norbornadiene Nuc, nucleophile OTf, triflate Ph, phenyl Pr, propyl py, pyridine THE, tetrahydrofuran TMEDA V,V,M,M-tetramethylethylenediamine. 

Larhed et al. investigated enantioselective Heck reactions with 2,3-dihydrofuran as alkene [86]. In the coupling with phenyl triflate, conditions previously reported by Pfaltz [87] were attempted under microwave irradiation. Interestingly, the catalytic system Pd2(dba)3/(4S)-4-t-butyl-2-[2-(diphenylphosphanyl)phenyl]-4,5-dihydro-l,3-oxazole, identified by the Swiss team, was found suitable for high-temperature microwave-assisted enantioselective Heck reactions (Scheme 76). Using a proton sponge as a base and benzene as a solvent gave the best conversions (Scheme 76). At tempera-... 

For aryl halides and sulfonates, even active ones, a unimolecular SnI mechanism (lUPAC Dn+An) is very rare it has only been observed for aryl triflates in which both ortho positions contain bulky groups (fe/T-butyl or SiRs). It is in reactions with diazonium salts that this mechanism is important ... 

Silica sol-gel inunobihzed La(OTf)3 (Scheme 48.2B) previously used in the acylation of a series of alcohols and activated aromatic compounds using acetic anhydride as acylating agent, showed a poor activity compared with other various sihca sol-gel inunobihzed triflate derivatives (tert-butyl-dimethylsilyl-trifluoromethane-sulfonate (BDMST), or trifhc acid (HOTf)). Acylation at the aromatic ring occurred over the BDMST and HOTf catalysts, while the La(OTl)3 catalysts only led to O-acetylated products [22]. Such behavior is characteristic... 

Metal-Catalyzed. Cyclopropanation. Carbene addition reactions can be catalyzed by several transition metal complexes. Most of the synthetic work has been done using copper or rhodium complexes and we focus on these. The copper-catalyzed decomposition of diazo compounds is a useful reaction for formation of substituted cyclopropanes.188 The reaction has been carried out with several copper salts,189 and both Cu(I) and Cu(II) triflate are useful.190 Several Cu(II)salen complexes, such as the (V-f-butyl derivative, which is called Cu(TBS)2, have become popular catalysts.191... 

The di-t-butyl-substituted silanols 40 and 41 result from hydrolysis during column chromatography of the corresponding triflates and have also been structurally characterized (240). The adamantyl compound... 

Transformations through 1,2-addition to a formal PN double bond within the delocalized rc-electron system have been reported for the benzo-l,3,2-diazaphospholes 5 which are readily produced by thermally induced depolymerization of tetramers 6 [13] (Scheme 2). The monomers react further with mono- or difunctional acyl chlorides to give 2-chloro-l,3,2-diazaphospholenes with exocyclic amide functionalities at one nitrogen atom [34], Similar reactions of 6 with methyl triflate were found to proceed even at room temperature to give l-methyl-3-alkyl-benzo-l,3,2-diazaphospholenium triflates [35, 36], The reported butyl halide elimination from NHP precursor 13 to generate 1,3,2-diazaphosphole 14 upon heating to 250°C and the subsequent amine addition to furnish 15 (Scheme 5) illustrates another example of the reversibility of addition-elimination reactions [37],... 

Denk et al. reported the first synthesis of 4,5-unsubstituted [l,3,2]diazaphosphe-nium chloride, 47C1 from the dilithio reduction product 50 of 1,2-diiminoethane, via cyclic dichloro-diazasilane 51 by means of metathetical reaction of the latter with PC13 (Scheme 15) [46], l,3-Di-ferf-butyl-[l,3,2]diazaphosphenium tetrachlo-rogallate [46], hexafluorophosphate [52], tetrafloruborate [49], and l,3-dimesityl-[l,3,2] diazaphosphenium triflate [49] were obtained as stable crystalline solids from the... 

Copper(II) triflate is quite inefficient in promoting cyclopropanation of allyl alcohol, and the use of f-butyl diazoacetate [164/(165+166) = 97/3%] brought no improvement over ethyl diazoacetate (67/6 %)162). If, however, copper(I) triflate was the catalyst, cyclopropanation with ethyl diazoacetate increased to 30% at the expense of O/H insertion (55%). As has already been discussed in Sect. 2.2.1, competitive coordination-type and carbenoid mechanisms may be involved in cyclopropanation with copper catalysts, and the ability of Cu(I) to coordinate efficiently with olefins may enhance this reaction in the intramolecular competition with O/H insertion. 

Several palladium catalysts for formation of aryl sulfides from aryl halides have been investigated more recently. A combination of Pd2(dba)3 and DPEphos catalyzed the formation of a broad range of diaryl sulfides in the presence of 1 mol.% palladium and NaO-t-Bu base in toluene solvent.12,rThe highest yields of alkyl aryl sulfides were obtained from aryl triflates and n-butyl thiol catalyzed by a combination of palladium acetate and BINAP. However, these reactions contained 10 mol.% catalyst, were long, and required deactivated aryl triflates. A combination of Pd2(dba)3 and DPPF catalyzed the coupling of thiols with resin-bound aryl halides.121... 

Microwave promoted, palladium-catalyzed, DPPP-controlled arylation of butyl vinyl ether with 4-tert-butylphenyl triflate afforded the branched arylation product and the corresponding methyl ketone, indicating the occurrence of selective internal a-arylation. Addition of water to the reaction mixture and microwave-heating for 2.8 min at 55 W smoothly produced the hydrolyzed product, 4-tert-butylacetophe-none, with an isolated yield of 77% (Eq. 11.2) [17]. 

Equation 11.2 Heck-coupling of 4-tert-butylphenyl triflate and butyl vinyl ether in the presence of water (DPPP = 1,3-bis (diphenyl phosphino) propane). 

Equation 11.13 Internal vinylation of butyl vinyl ether with a vinyl triflate. 

Exchange of the butyl vinyl ether for 2-hydroxyethyl vinyl ether enabled the facile transformation of vinyl triflates or bromides into protected a,/i-unsaturated methyl ketones (Eq. 11.14) [27]. One interesting aspect of this reaction is that a masked methyl ketone can easily be introduced into a structure even in the presence of other free ketone groups. 

Analogously, 5-tributylstannylimidazole 29 was easily obtained from the regioselective deprotonation of 1,2-disubstituted imidazole 28 at C(5) followed by treatment with tributyltin chloride [24]. In the presence of 2.6 equivalents of LiCl, the Stille reaction of 29 with aryl triflate 30 afforded the desired 1,2,5-trisubstituted imidazole 31 with 2,6-di-tert-butyl-4-methylphenol (BHT) as a radical scavenger. Reversal of the nucleophile and electrophile of the Stille reaction also provided satisfactory results. For example, the coupling reaction of 5-bromoimidazole 33, derived from imidazole 32 via a regioselective bromination at C(5), and vinylstannane 34 produced adduct 35 [24],... 

The reactive triflate 323 prepared from the aldol adduct 322 promoted an intramolecular attack by the BOC carbonyl group (expecting subsequent loss of a tert-butyl cation) to afford the dihydro derivative 325 through the oxonium 324 (Scheme 45) <2003OBC3749>. 

Methods for indirect oxidation have also been developed. The combination of KF/ wCPBA in acetonitrile and water has been used to generate KOF CH3CN reagent, a mild and selective oxidant that reacts at 0 °C with no overoxidation [78]. This reagent functions by providing a fluorosulfonium ion intermediate, which is hydrolyzed in the presence of water to the desired sulfoxides. As a result of the indirect oxidation method, the typical stereoselectivity of mCPBA-type oxidations is not observed here. The KOFCH3CN oxidant is similar in scope and mechanism to 1-fluoropyridinium triflates, Selectfluor [302] and the more classical t-butyl hypochlorite [288]. 

Helmchen and co-worker investigated the use of phosphinooxazolines as ligands for copper(II) catalyzed Diels-Alder reactions (Scheme 19) (214). Optimal selectivities are found for a-naphthyl-substituted phosphinooxazoline (299). These catalysts require 2.5 h to induce complete conversion to cycloadduct, compared to 18 h using the triflate complex 269c under identical conditions. Helmchen invokes a square-planar metal geometry to explain the stereochemistry of the adducts, similar to the model proposed by Evans. He suggests that the bulky phosphine substituents are required to orient binding of the dienophile in such a way as to place the olefin directly below the terf-butyl substituent on the oxazoline. 

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