Tandem Condensation/Rearrangement Reaction of 2‐Aminohetarene N‐Oxides for the Synthesis of Hetaryl Carbamates

Abstract

A new approach to hetaryl carbamates through a tandem condensation/rearrangement reaction of 2‐aminohetarene N‐oxides was developed. The developed reaction is suitable for both five‐ and six‐membered heterocycles and proceeds through the condensation of 2‐aminohetarene N‐oxide with trimethyl orthoformate followed by intramolecular N‐oxide oxygen transfer. For five‐membered hetarene N‐oxides (furoxans), the intramolecular rearrangement is catalyzed by a cyanide anion, while for six‐membered hetarene N‐oxides (azines), Lewis acid catalysis is sufficient. The developed protocol is characterized by operational simplicity and high efficiency, resulting in carbamoyl derivatives in good and high yields.magnified image

Recent Advances in the Synthesis of C2‐Functionalized Pyridines and Quinolines Using N‐Oxide Chemistry

“…Makhova's group recently described the BF 3 ‐catalyzed preparation of hetaryl carbamates 392 by condensation of 2‐aminohetarene N ‐oxide 391 with trimethyl orthoformate followed by intramolecular N ‐oxide oxygen transfer (Scheme 114). [149] …”

Five-Membered Hetarene N-Oxides: Recent Advances in Synthesis and Reactivity

“…A novel reactivity mode of 3-aminofuroxans 49 was also recently established. 53 A scope of the Bystrov-Zhilin-Fershtat rearrangement was further extended on the Sc(OTf)3-catalyzed condensation of aminofuroxanyl amidoxime 54 with aldehydes. Amidoxime functionality was annulated to the 1,2,4-oxadiazole ring, while 4-aminofuroxan moiety was converted to the (carbamoyl)furazan one.…”

“…A novel reactivity mode of 3-aminofuroxans 49 was also established recently. 53 Compounds 49 were converted into the corresponding imino ethers 50, which were found to participate in a cyanide-catalyzed intramolecular rearrangement into furazanyl carbamates 51 (we propose naming this reaction as the Bystrov-Zhilin-Fershtat rearrangement). A plausible mechanism for the Bystrov-Zhilin-Fershtat rearrangement includes nucleophilic addition of the cyanide anion to the C(sp 2 ) atom of the imino ether functionality.…”

Copper-Catalyzed Oxidative Coupling of Quinazoline-3-Oxides: Synthesis of O-Quinazolinic Carbamates

“…In recent years, organic carbamates have attracted much attention from the synthetic community due to their diverse interesting properties. − In addition to being an important class of privileged structures in pharmaceuticals in the forms of drugs and prodrugs, the carbamate motif is also broadly existed in agrochemicals and polymers. − The most common methods to organic carbamates rely on the nucleophilic addition of alcohols to isocyanates or isocyanate intermediates generated in situ form acyl azides via Curtius rearrangement (Scheme ). − In addition, the utilization of CO 2 , ,,− CO, ,− or COCl 2 − as C1 synthon to combine with amines and alcohols provides an alternative convenient access to organic carbamates. − Very recently, some supplementary strategies have also been developed through transition metal-catalyzed or novel rearrangement process. − …”