Bismuth trifluoroacetates

A number of new conditions and catalysts have been used for the synthesis of quinazolinones 50 from anthranilic acids, amines and ortho esters, including bismuth trifluoroacetate with an ionic liquid <06TL3561>, lanthanum nitrate or tosic acid under solvent-free conditions at room temperature <06TL4381> and Nafion-H <06SL2507>. 

Scheme 11.4 shows some other representative Friedel-Crafts acylation reactions. Entries 1 and 2 show typical Friedel-Crafts acylation reactions using A1C13. Entries 3 and 4 are similar, but include some functionality in the acylating reagents. Entry 5 involves formation of a mixed trifluoroacetic anhydride, followed by acylation in 85% H3PO4. The reaction was conducted on a kilogram scale and provides a starting material for the synthesis of tamoxifen. Entry 6 illustrates the use of bismuth triflate as... 

Although it was first prepared by Verma et al. in 1983 starting from Bi(III) trifluoroacetate [58], our group developed another strategy for the preparation of Bi(OTf)3 [32]. The key point of our synthetic strategy is based on the acidic cleavage of the three carbon-bismuth bonds of triphenylbismuth by triflic acid in dichloromethane (Scheme 1). A study of the hydration of Bi(0Tf)3xH20 revealed that this compound can exist as three different hydrates, the nonahydrate, the tetrahydrate, and the dehydrate [35], The structures of the nona- and tetrahydrate forms have been determined by ab-initio calculations [35] and XRD [36]. 

Table IV summarizes the trifluoroacetato complexes of the Group V elements that have been characterized. The simple trifluoroacetates of arsenic, antimony, and bismuth(III) have been isolated only recently, following the reaction of the corresponding trichloride with Ag(02CCF3) in CH2CI2 (123) and, for the bismuth derivative, by the reaction of Bi203 with (CFaCO)aO (200). These are reasonably volatile compounds which are extremely moisture-sensitive.

These two systems of phenol 0-phenylation [0-phenylation with tetraphenylbismuthonium trifluoroacetate (6) or with triphenylbismuth diacetate (47)] may be ligand coupling reactions involving hexavalent transient intermediates, but no proof of such structures was ever detected. The former reaction does not involve free radicals, as addition of 1,1-diphenylethylene (72) (DPE), did not affect the overall yield. These reactions were explained by a direct aromatic Sn2 displacement, facilitated by the partial charge on the carbon bonded to the bismuth atom.24 (see section 6.6)... 

The same type of reactivity patterns was observed in the case of the 0-phenylation of alcohols by tetraphenylbismuthonium trifluoroacetate under neutral or acidic conditions. These observations led to the conclusion that these reactions of 0-phenylation of alcohols and phenols are better explained by an aromatic Sn2 substitution, involving nucleophilic attack of the bismuth-bearing aromatic carbon by the hydroxyl function of the substrate. The electron-withdrawing trifluoroacetoxy substituent induces a partial positive charge on the ipso carbon, which facilitates the substitution.24,51... 

Epoxides also suffer nucleophilic attack by amines, forming ethanolamine derivatives. This reaction can take place under a variety of conditions and with the influence of several catalysts. Styrene oxide 61 undergoes ring opening in the absence of catalyst under strictly thermal conditions (90 C in a sealed tube) to give predominantly the amino-alcohol 62, the product of attack at the more substituted (a) position <04SC2393>. The reaction time can be reduced by using a combination of catalytic bismuth(III) trifluoroacetate and brief microwave irradiation, as... 

Diphenylbismuth trifluoroacetate 74 (2,2-Diphenylethyl)bismuth bis(benzenethiolate) 123 Diphenyl(phenylethynyl)bismuthine 26... 

Tetraphenylbismuth trifluoroacetate under neutral or slightly acidic conditions phenylates primary alcohol in reasonable yields (65-75%), but gives only moderate yields with secondary alcohols. In contrast, the reaction of bismuth [Bi(V)] reagents with alcohols under basic conditions [BTMG (2) or TMG (1)] gives, exclusively, oxidation [90]. 

An excess of boiling trifluoroacetic anhydride reacts with sodium arsenite to give the compound NaAs0(CF3C02)2 in good yield, and similar bismuth reactions also take place. Polarographic and potentiometric measurements in aqueous solution point to the formation of a complex [As(OH)2HX]" between arsenic(iii) and nitrilotriacetic acid (HaX). ... 

Thiophenes are generally obtained by sulfuration of 1,4-dicarbonyl compounds (Paal s)mthesis). The preparation of the highly substituted 2-(4-bromophenyl)-5-(3,4-dimethoxyphenyl)-3,4-dimethylthiophene from the respective 1,4-diketone represents a recent example. This type of reaction can be performed as a solid-phase synthesis with polymer-bound diketones (132) and LR (eq 44). Trifluoroacetic acid releases the thiophene (133) from the solid support. Bismuth triflate in 1,3-dialkylimida-zolium fluoroborate has been utilized as a catalytic ionic liquid system for the synthesis of thiophenes from 1,4-diketones and LR with significantly improved yields. 

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