DBU-Catalyzed Desymmetrization of Cyclohexadienones: Access to Vicinal Diamine-Containing Heterocycles

Abstract

A DBU-catalyzed desymmetrization strategy between cyclohexadienones and isocyanates was discovered, affording a series of vicinal diamine-containing heterocycle derivatives in moderate to good yields and excellent diastereoselectivity under mild conditions. Furthermore, this reaction could be performed on a 10 g scale using 1.0 mol % of catalyst loading.

Synthesis of Hydrobenzoimidazoles from para‐Quinamines and 1,3,5‐Triazinanes via a Formal [3+2] Annulation Reaction

“…For intermolecular reactions, there were two major reaction modes (i. e., [3+2] and [3+3]), and hydroindole derivatives as the products were obtained in the most reports. In the case of [3+2], the only exception was Huang's report that a DBU‐catalyzed desymmetrization of para ‐quinamines with isocyanates, which delivered hydrobenzoimidazol‐2‐ones as the final products [9f] . Based on these elegant contributions, we hoped to combine these two nitrogen‐containing building blocks (i. e., 1,3,5‐triazinanes and para ‐quinamines) to synthesize 1,3‐diaza heterocycles.…”

Recent Advances in the Catalytic Synthesis of Imidazolidin-2-ones and Benzimidazolidin-2-ones

“…A similar approach was applied to the desymmetrization of cyclohexadienones with isocyanates in presence of a catalytic amount of DBU (1,8-Diazabicyclo(5.4.0)undec-7-ene) [180]. The authors reported the synthesis of a broad range of bicyclic imidazolidin-2-ones with high diastereomeric ratios (Scheme 63).…”

“…The same base was also employed as a catalyst in the cyclization of β-amino carbamates to promote the formation of the imidazolidin-2-one scaffold [180].…”

“…DBU-catalyzed sequential nucleophilic/aza-Michael addition [180]. DBU: 1,8-Diazabicyclo(5.4.0)undec-7-ene.…”

Chiral Phosphoric Acid Catalyzed Asymmetric Desymmetrization of para-Quinamines with Isocyanates: Access to Functionalized Imidazolidin-2-one Derivatives

“…In contrast to the basic conditions employed in the above reaction, we questioned whether such a reaction could be realized under acid condition. In 2018, the Huang group reported a DBU-catalyzed desymmetrization strategy between cyclohexadienones and isocyanates, affording a series of racemic imidazolidin-2-one derivatives, which were widely existed in natural products and biological compounds . Inspired by these pioneering studies above and as our continuous interest in exploring new asymmetric reactions of cyclohexadienone derivatives, herein we reported a catalytic enantioselective variant of desymmetrization between para -quinamines and isocyanates by chiral phosphoric acid (Scheme b).…”