Lactonization trifluoroacetic anhydride

Miki and Hachiken reported a total synthesis of murrayaquinone A (107) using 4-benzyl-l-ferf-butyldimethylsiloxy-4fT-furo[3,4-f>]indole (854) as an indolo-2,3-quinodimethane equivalent for the Diels-Alder reaction with methyl acrylate (624). 4-Benzyl-3,4-dihydro-lfT-furo[3,4-f>]indol-l-one (853), the precursor for the 4H-furo[3,4-f>]indole (854), was prepared in five steps and 30% overall yield starting from dimethyl indole-2,3-dicarboxylate (851). Alkaline hydrolysis of 851 followed by N-benzylation of the dicarboxylic acid with benzyl bromide and sodium hydride in DMF, and treatment of the corresponding l-benzylindole-2,3-dicarboxylic acid with trifluoroacetic anhydride (TFAA) gave the anhydride 852. Reduction of 852 with sodium borohydride, followed by lactonization of the intermediate 2-hydroxy-methylindole-3-carboxylic acid with l-methyl-2-chloropyridinium iodide, led to the lactone 853. The lactone 853 was transformed to 4-benzyl-l-ferf-butyldimethylsiloxy-4H-furo[3,4- 7]indole 854 by a base-induced silylation. Without isolation, the... 

C-aryl glycals in 75-92% yields. It consisted in the addition of aryllithium reagents to variously protected 2-deoxy-aldono-l,5-lactones, followed by treatment with a mixture of pyridine (Py), 4-(Dimethylamino)pyridine (DMAP), and trifluoroacetic anhydride (TFAA). 

Lithium 2-thiophenethiolate, readily prepared from thiophene, -butyllithium, and sulfur, reacts with / -butryo-lactone to give carboxylate derivative 98 which can be readily acidified to the free acid. Cyclization in the presence of trifluoroacetic anhydride gives thieno[2,3-3]thiopyran (Scheme 27) <1996TA2721>. 

Fleet and co-workers (75a) synthesized various tetrazoles from manno- and rhamnopyranoses, as well as furanoses, based on the intramolecular 1,3-dipolar cycloadditions of azides with nitriles (Scheme 9.75). All of these tetrazoles were tested for their inhibitory activities toward both glycosidases and other sugarprocessing enzymes. D-Mannopyranotetrazole (397) was prepared from L-gluono-lactone (393). Azide 394 on ring opening with ammonia followed by dehydration with trifluoroacetic anhydride gave the azido nitrile 395. Intramolecular 1,3-dipolar cycloaddition of 395 in refluxing toluene followed by deprotection produced the D-mannopyranotetrazole 397 in 86% overall yield. 

Exposure of 3-(tetrahydro-2-furyl)-3-trimethylsilylpropanoic acids 178 to trifluoroacetic anhydride allows intramolecular acylative ring-opening reaction to give the corresponding eight-membered lactones 180 in moderate to good yields (Scheme 46) <1999SL1757>. However, when R1 = R2 = Me, lactones 180 are not formed. The acyloxonium ion 179 is a probable intermediate in these reactions. Similarly, acids 182 afford lactones 183 (Scheme 47). 

The mixed trifluoroacetic anhydride method played an important role in the first synthesis of the 14-membered macrolide zearalenone (70) by Taub et al. [42]. Hydroxy acid 68 was treated with trifluoroacetic anhydride (TFAA) and lactone 69 was obtained in 15% yield (Scheme 22),... 

The migration of oxygen from a quaternary center in a cyclohexadienone may be preferred to a carbon shift, when present as an ether or ester function rather than free hydroxy. Thus the p-quinol acetate (117) yields the orcinol monoacetate (118 79%) on treatment at room temperature with trifluoroacetic anhydride, and the p-quinol ether (119) forms the resorcinol diethyl ether (120 71%) in ethanolic sulfuric acid. In the second case, hemiketalization must intervene also some methyl shift (12%) is observed. With the quinol (121), treatment with acetic anhydride-sulfuric acid leads to the lactone (122) acetylation or lactonization probably precedes oxygen shift. A number of related examples can be found in the steroid area. - Thermal 1,3-shifts of p-quinol acetates can also be induced acetate (117) yields catechol acetate (123 50-60%, 45 °C) by way of isomerization of the first-formed acetate (124). In the o-quinol acetate series, 1,2-acetoxy shift is seen in (125) (126 92%) and in (127) (128 90%), both in... 

Not surprisingly. Bycroft reported failure to effect formation of the macrocycle from the seco acid via an intramolecular lactonization. All attempts at the use of either DCC or trifluoroacetic anhydride under a variety of conditions failed... 

Lactonization of this mixture with trifluoroacetic anhydride and... 

The method also works well for bicyclic ketones such as nor-camphor (Eq. 27) and acyclic ketones such as pinacolone which afforded tert-butyl acetate in 96% yield. Reactions of benzocycloalkanones such as a-tetralone with the UHP-trifluoroacetic anhydride system also give the expected lactones in better yields than have previously been reported. The results are summarised in Eqs. (28) to (30). 

B.ii. Synthetic Approaches to Macrocyclic Lactones. There are many examples of biologically important, naturally occurring lactones. A variety of cyclization techniques have been developed, but all are based on the idea that the carbonyl end of an cu-substituted acid is activated to facilitate attack by or at the other functionalized end. Trifluoroacetic anhydride, for example, was used to convert 220 to 222 in 31% yield.xhe initially formed mixed anhydride (221) activated the carbonyl to attack by the hydroxyl moiety, leading to 222 in the Taub et al. synthesis of zearalenone. An alternative synthetic route required a macrocyclization reaction but it involved Friedel-Crafts acylation (sec. 12.4.D). Cyclization has also been observed using a mixture of trifluoroacetic acid and trifluoroacetic anhydride. ... 

The conversion of cyclic ketones to produce lactones via a Bayer Villiger-type reaction can be performed using UHP as shown in reaction 5. These types of reactions involve using UHP with trifluoroacetic anhydride in the presence of disodium hydrogen phosphate which acts as a buffer. The active species in these solutions is trifluoroperoxyacetic acid which is generated in situ. 

In a variation of the known conversion of phthalideisoquinolines into rhoeadines, the -lactone 1 derived from jS-hydrastine was converted to its iV-oxide. The secondary amine 2 was obtained from the iV-oxide by reaction with trifluoroacetic anhydride, in a modified Polonovski reaction. The papaverrubine 3 was then generated from the amine 2 as shown below ... 

Already in 2001, Basavaiah and Satyanarayana [49] reported Sj,2 bisalkylation of indanone (68a) or 1-tetralone (68b) with Bayhs-Hillman acetates 30 followed by a saponification and trifluoroacetic anhydride-mediated bis-lactonization of 70 as a facile route to bis-a-aryhdene-S-lactones 71 (Scheme 4.18). Reactions proceeded in... 

Yonemitsu et al. [46] modified the Yamaguchi conditions in which the mixed anhydride is not isolated and DMAP is directly introduced at room temperature from the beginning. Shiina et al. [47] described the use of 2-methyl-6-nitrobenzoic anhydride (MNBA) as an alternative to 2,4,6-trichlorobenzoyl chloride. Pivaloyl chloride [48], trifluoroacetic anhydride [49], AC2O [50], and B0C2O [51] are also employed for the lactonization via mixed anhydride under basic conditions. Furthermore, Yamamoto et al. [52] described the use of Sc(OTf)3 as a Lewis acid. 

If other reactive moieties are present a cyclopropanecarbonyl compound can be converted to the corresponding cyclopropylalkane using various conditions. Thus, 3,4-benzotricy-clo[4.3.1.0 ]dec-3-en-2-one yielded 3,4-benzotricyclo[4.3.1.0 ]dec-3-ene in excellent yield on treatment with sodium in liquid ammonia. di-l-Methylcyclopropane-l,2-dicarboxylic anhydride underwent a similar reaction to afford isomeric lactones on treatment with lithium aluminum hydride or sodium borohydride in tetrahydrofuran. On the other hand, ionic hydrogenation (triethylsilane in trifluoroacetic acid and water) of cyclopropyl phenyl ketone gave a complex reaction mixture and very little benzylcyclopropane. ... 

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