Nucleophilic Acyl Substitutions of Anhydrides with Protic Nucleophiles Catalyzed by Amphoteric, Oxomolybdenum Species

Abstract

[reaction: see text] Among six different group VIb oxometallic species examined, dioxomolybdenum dichloride and oxomolybdenum tetrachloride were the most efficient catalysts to facilitate nucleophilic acyl substitution (NAS) of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. In contrast to the well-recognized redox chemical behaviors associated with oxomolybdenum(VI) species, the catalytic NAS was unprecedented and tolerates virtually all kinds of functional groups. By using benzoic anhydride as a mediator for in situ generation of an incipient mixed anhydride-MoO(2)Cl(2) adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-alpha-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the Mo=O unit in oxomolybdenum chlorides was found to be responsible for the catalytic NAS profile as supported by a control NAS reaction of using an authentic adduct-MoOCl(2)(O(2)CBu(t)())(2) between pivalic anhydride and MoO(2)Cl(2) as the catalyst.

Lewis acid catalyzed N-acylation of carbamates and oxazolidinones

“…Therefore, we have decided to perform the N-acylation of carbamate with carboxylic acid in presence of benzoic anhydride by adopting the mixed anhydride method. 10 Consequently, the reaction of phenyl acetic acid 3a with benzyl carbamate 1a in presence of benzoic anhydride and 5 mol% ZnCl 2 in CH 2 Cl 2 at room temperature for 1.5 h afforded the corresponding product 4a in 85% yield (entry 1, Table 3). Phenyl carbamate 1b was acylated to 4b by using the same carboxylic acid 3a under the similar conditions.…”

1,1'-(Ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) as a recyclable catalyst for acylation

“…19,21,24,43 It is worth noting that none of the procedures reported in literature has focused on the acylation of alcohols, amines, and thiols with isobutyric anhydride. In order to extend the scope of the methodology, acylation of alcohols, amines, and thiols with other anhydrides was carried out under the identical condition as described using acetic anhydride.…”

“…17,18 Metal triflates [19][20][21][22][23][24][25][26][27][28][29] and perchlorates [30][31][32][33] have been used for the purpose owing to their acidic nature. Other reagents / catalysts employed are TMSCl, 34 HClO 4 -SiO 2,35 Sc(NTf 2 ) 3,36 Nafion-H, 37 Yttria-Zirconia, 38 43 Although metal triflates, perchlorates and other acidic catalysts are effective for the acylation reaction, their use is limited due to explosive nature of metal perchlorates and strong acidic character of triflates which results in side reactions. The drawbacks associated with some of the procedures reported in literature are arduous preparation of catalysts, difficulties in work-up and isolation, the need for an inert atmosphere, harsh reaction conditions, expensive reagents, low yields, longer reaction times, dry solvents and incompatibility with other protecting groups.…”

N,N-dichloro-4-methylbenzenesulphonimide as a novel and efficient catalyst for acetylation of alcohols under mild conditions

“…1,2 The various catalysts developed for the activation of anhydrides include nucleophilic, 3,4 and electrophilic [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] reagents. However, these acetylation methodologies suffer from one or more disadvantages such as stringent conditions, use of hazardous materials (e.g.…”