Preparation and in situ use of unstable N-alkyl α-diazo-γ-butyrolactams in Rh^II-catalyzed X–H insertion reactions

Abstract

N-Alkyl α-diazo-γ-butyrolactams, previously found to be unstable and to undergo unproductive dimerization to bishydrazones, were successfully converted immediately to various X–H insertion products with alcohols, aromatic amines and thiols via an in situ RhII-catalyzed reaction. With aliphatic amines or unreactive, sterically hindered anilines, the reactions tended to yield enamine adducts.

RhII‐Catalyzed De‐symmetrization of Ethane‐1,2‐dithiol and Propane‐1,3‐dithiol Yields Metallo‐β‐lactamase Inhibitors

“…The arsenal of diazo compounds 1 a – i selected for this study has been reported previously as prepared via the recently developed ‘sulfonyl‐azide‐free’ (SAFE) protocol ( vide infra ) [10–12] . α‐Diazo‐γ‐butyrolactams 1 j – n were prepared via the Danheiser diazo transfer protocol using 4‐nitrobenzene sulfonyl azide as diazo transfer reagent [13,14] . It should be noted that all aforementioned diazo compounds are stable to storage except for 1 j which undergoes a rapid dimerization [14] and had, therefore, been used immediately [13] in the subsequent Rh(II)‐catalyzed S−H insertion reaction without isolation (Figure 2).…”

“…Known diazocarbonyl compounds 1 a – n were prepared according to literature procedures,[ 10 , 11 , 12 , 13 , 14 ] other reagents were obtained from commercial sources and used without any additional purification. Solvents were distilled over suitable drying agents.…”

“…[10][11][12] α-Diazo-γ-butyrolactams 1 j-n were prepared via the Danheiser diazo transfer protocol using 4-nitrobenzene sulfonyl azide as diazo transfer reagent. [13,14] It should be noted that all aforementioned diazo compounds are stable to storage except for 1 j which undergoes a rapid dimerization [14] and had, therefore, been used immediately [13] in the subsequent Rh(II)-catalyzed SÀ H insertion reaction without isolation (Figure 2).…”

Preparation and Synthetic Applications of Five-to-Seven-Membered Cyclic α-Diazo Monocarbonyl Compounds

“…o -Substitution in the aryl group perturbs that conjugation and makes such systems more ‘ N -alkyl-like’ [ 128 ]. In order to be able to use such unstable α-diazo-γ-butyrolactams in subsequent transformations, a convenient, one-pot protocol has been developed that does not require the isolation of the diazo compounds in the interim [ 129 ].…”