N−H Insertion Reactions of Primary Ureas:  The Synthesis of Highly Substituted Imidazolones and Imidazoles from Diazocarbonyls

Abstract

Primary ureas have been used as substrates in rhodium-catalyzed N-H insertion reactions with an array of diazocarbonyls. The insertion reaction is efficient and gives excellent selectivity and yields. The products from the insertion reaction with diazoketones cyclize readily in the presence of acid to yield the corresponding imidazolones that can be further derivatized by N-alkylation with alkyl, allyl, and benzyl halides. Alternatively, the imidazolones were treated with phosphorus oxybromide to form the corresponding 2-bromoimidazoles that were further functionalized using a Suzuki coupling reaction.

Asymmetric Synthesis of the Aminocyclitol Pactamycin, A Universal Translocation Inhibitor

“…The reaction of 2,4-pentanedione 10 with para-acetamidobenzenesulfonyl azide (pABSA) 20 and Et 3 N afforded the corresponding diazoketone in nearly quantitative yield. An N-H insertion reaction analogous to that used in our previous studies delivered α-ureidodiketone 8 in 67% yield, 21 and Tsuji-Trost allylation provided the necessary diketone precursor 6 in 81% yield. Working first to optimize the racemic reaction, we began screening reducing agents and conditions for selectivity.…”

Methods for the synthesis of 1-substituted 1H-imidazol-2(3H)-ones

“…[51][52][53] Heating of diazo compounds 21 and monosubstituted ureas 3 in the presence of a catalytic amount of Rh 2 Oct 4 allowed to obtain imidazolones 1 51,52 (Scheme 29). The intermediates in this reaction were ureidoketones 8, isolated in three cases.…”

α-Amino acid derivatives with a Cα-P bond in organic synthesis

“…32 A wide range of amines (R 1 = aryl, R 2 = H) and amides (R 1 = acyl, R 2 = H or alkyl) was used in this reaction to get the amination product in moderate to good yields. [32][33][34] It should be noted, that both tosyl azide and diazo compound 27 are potentially explosive. …”