A Simple Preparation of Aryl Methanesulfonates by Thermal Decomposition of Dry Arenediazonium o-Benzenedisulfonimides in Methanesulfonic Acid

Abstract

Aryl methanesulfonates 3 (18 examples) were easily prepared by thermal decomposition of dry arenediazonium o -benzenedisulfonimides 1 in methanesulfonic acid ( 2 ). The reactions were carried out at temperatures between 60 and 120¡C for times between 0.5 and 8 h. The aryl methanesulfonates were obtained in reproducible yield of 70Ð90%, with few exceptions. In all cases the o -benzenedisulfonimide ( 4 ) could be recovered in good yields which can then be reused to prepare the salts 1 . When thermal decomposition of salts 1 was carried out in trifluoromethanesulfonic acid ( 5 ) at 90Ð120¡C for 1Ð2 h, aryl trifluoromethanesulfonates 6 were obtained in 73Ð78% yield (3 examples).Aryl methanesulfonates 3 are a notable class of compounds with various applications. They are used in organic synthesis, in reactions where it is necessary to protect the phenolic hydroxyl group 1 or where there is the removal of the mesylate group, i.e. in metal-catalyzed homoand cross-coupling reactions 2 and in substitution reactions. 2b,3 Furthermore, the use of aryl methanesulfonates has been the subject of numerous patent claims, even recent ones, such as dyes, 1b,c drugs 4 and especially agrochemicals. 5 It is known that aryl trifluoromethanesulfonates can be prepared by triflation of phenols or of their O -silyl derivatives, 6 as well as by thermal decomposition of arenediazonium tetrafluoroborates in trifluoromethanesulfonic acid 7 or, though less favourably, in trifluoromethanesulfonic anhydride. 8 Instead, to our knowledge, aryl methanesulfonates are prepared exclusively by treating phenols with methanesulfonyl chloride in the presence of a base. 9Ð13 Recently 14 we prepared a representative series of dry arenediazonium salts 1 that are very stable due to the anion of the o -benzenedisulfonimide ( 4 ), promptly prepared and able to be stored safely for long periods, without any risk and ready for use. In a wide-ranging investigation 14,15 on the synthetic uses of the salts 1 , we have found that thermal decomposition in methanesulfonic acid ( 2 ) brings about their easy conversion into the corresponding aryl methanesulfonates 3 (Scheme 1). The reaction involved heating of the salts 1 in methanesulfonic acid ( 2 ) between 60 to 120¡C, temperatures that are at least 20ûC lower than the decomposition temperatures of the reacting salts themselves. Reaction time was 0.5 to 8 h and aryl methanesulfonates 3 were obtained in good yields. It must be stressed that in all the reactions with a positive outcome (Table, entries 1Ð4, 6Ð8, 10Ð15 and 17Ð21) there was also the recovery of good amounts of the o -benzenedisulfonimide ( 4 ), reusable for the preparation of the salts 1 . Conditions and yields of the studied reactions are listed in the Table. The reactions failed when a methoxy, fluoro or nitro substituent was present in the ortho position (Table, entries 5, 9 and 16). Thus, the formation of the aryl methanesulfonates 3 proceed through a D N + A N mechanism of dediazoniation 16 and that in the cases indicated in entries 5, 9 and 16 the t...

A New Effective Synthesis of Arene Mono- and Disulfonyl Chlorides

“…10 Salt 3f was converted into 5f (62% overall yield) in the presence of 10 equiv of H 2 O. Comparable results were obtained starting from the o-benzenedisulfonimide salt 3g 11 (entries 9 and 10).…”

o-Benzenedisulfonimide: An Organic Reagent and Organocatalyst of Renewed Interest

“…Aryl methanesulfonates 75 (and three aryl trifluoromethanesulfonates) were easily prepared by thermal decomposition of some representative salts 67 in methanesulfonic acid (or trifluoromethanesulfonic acid), at a temperature between 60 and 120 °C, in reproducible good yields (Scheme 24) [42]. The authors suggested that the reaction follows a D N +A N mechanism (Nucleofuge Detachment + Nucleophile Attachment) of dediazoniation.…”

A Novel Synthesis of Aryl Mesylates via One-Pot Demethylation-Mesylation of Aryl Methyl Ethers Using a Mixture of Phosphorus Pentoxide in Methane­sulfonic Acid

“…Colorless oil. 7 1 H NMR (250 MHz, CDCl 3 ): d = 7.69-7.12 (m, 4 H), 3.22 (s, 3 H). 13 C NMR (62.9 MHz, CDCl 3 ): d = 145.…”

“…6 A simple method for the synthesis of aryl mesylates has been reported by thermal decomposition of dry arene diazonium o-benzenedisulfonimides in methanesulfonic acid. 7 Methyl ethers have been employed as protecting group; however, this is generally avoided because they require harsh reagents or conditions for their removal and this often conflicts with the requirements of other functionalities. 8 Methanesulfonic acid is a Brönsted acid that used as catalyst and solvent for condensation or rearrangement reactions.…”