Catalytic Activity of 1,3-Dibromo-5,5-dimethylhydantoin (DBH) in the One-Pot Transformation ofN-Arylglycines toN-Arylsydnones in the Presence of NaNO₂/Ac₂O under Neutral Conditions: Subsequent Bromination of these Sydnones to their 4-Bromo Derivatives

Abstract

1,3-Dibromo-5,5-dimethylhydantoin (DBH) has been found to efficiently catalyze the one-pot conversion of various Narylglycines through N-nitrosation and cyclization to sydnones in combination with NaNO 2 and Ac 2 O in high yields (80-94%) under mild and neutral conditions. Also, it was shown that DBH can conveniently promote the bromination of these sydnones to their 4-bromo substituted congeners in excellent yields in DMF at room temperature.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

“…Azarifar and Ghasemnezhad-Bosra reported that DBH is capable of brominating sydnones to their 4-bromo-substituted congeners in excellent yields in DMF at room temperature (Scheme ). Initially, they developed a method for the conversion of various N -arylglycines to sydnones using the same reagent in the presence of sodium nitrite and acetic anhydride in dichloromethane. Bromination of the resulting sydnones was carried out using 2 mol equiv of DBH.…”

A mechanochemical approach to the synthesis of sydnones and derivatives

“…45 Bromination has been achieved with Br 2 /NaHCO 3 , 46 Br 2 /Ac 2 O, 47 KBrO 3 /HBr, 41 N -bromosuccinimide (NBS), 48 or 1,3-dibromo-5,5-dimethylhydantoin (DBH). 49 Finally, direct iodination of sydnones has been described with N -iodosuccinimide (NIS) in AcOH, 50 or ICl in AcOH. 51…”

Click and Bio-Orthogonal Reactions with Mesoionic Compounds

“…46 Finally, one-pot strategies were developed, avoiding the isolation of the toxic nitroso-amine intermediate. 47,48 In 2019, an alternative method using mechanochemistry was developed by the group of Lamaty. 49 Interestingly, the sydnone core offers various postfunctionalization possibilities, which have been the topic of several works, including reviews (Scheme 6b).…”

“…The nitrosylation step was also improved by Turnbull by using isoamyl nitrite, a milder reagent which requires only evaporation as workup . Finally, one-pot strategies were developed, avoiding the isolation of the toxic nitroso-amine intermediate. , In 2019, an alternative method using mechano-chemistry was developed by the group of Lamaty . Interestingly, the sydnone core offers various postfunctionalization possibilities, which have been the topic of several works, including reviews (Scheme b). ,− Indeed, the proton in position C 4 possesses an acidic character and can be abstracted in the presence of different organometallic species.…”