Rh‐Catalyzed Annulation of ortho‐C−H Bonds of 2‐Arylimidazoles with 1,4,2‐Dioxazol‐5‐ones toward 5‐Arylimidazo[1,2‐c]quinazolines

Abstract

A Rh-catalyzed unique and direct approach for constructing a series of 5-arylimidazo [1,2-c]quinazolines in moderate to excellent yields from simple and readily available 2-arylimidazoles and 3-phenyl-1,4,2-dioxazol-5-ones was described. This procedure proceeds with sequential ortho-CÀH bond amidation and cyclization, which represents a facile and straightforward pathway to access such frameworks.

Catalytic Transformations of Functionalized Cyclic Organic Carbonates

“…[58,59] With the introduction of ad irecting group possessing nucleophilic or electrophilic character,s ubsequent intramolecular cyclization after initial CÀHa midation is feasible giving rise to bicyclicc ompounds (Scheme 20). Thus,t he synthesis of quinazolines [60] and their N-oxides, [61] benzimidazoles, [62] azolopyrimidines [63] and thiadiazine-1-oxides [64] was achieved in as ingle step.T he use of an electrophilic enaminone directing group gave rise to 4-quinolone product. [65] Thea midation of more challenging C(sp 2 ) À Ha nd C(sp 3 ) À Hb onds can be also achieved though the scope is limited to the use of specially designed substrates such as oxime ethers,s ubstituted 8-methylquinolines and thioamides.…”

Katalytische Umwandlung von funktionalisierten cyclischen organischen Carbonaten

“…Transformation von 1,4,2-Dioxazol-5-onen 1,4,2-Dioxazol-5-one (Dioxazolone,c yclische Nitrilcarbonate) sind aufgrund ihrer schwachen N-O-Bindung bei milden Bedingungen leicht zu aktivieren. Aufd iese Weise konnten Chinazoline [60] und ihre N-Oxide, [61] Benzimidazolene, [62] Azolopyrimidine [63] und Thiadiazin-1-oxide [64] in einem Syntheseschritt hergestellt werden. Als besonders geeignet zeigten sich diese Substrate bei Reaktionen, die die C-H-Amidierung von (Hetero)Arenen beinhalten (Schema 19).…”

“…[58,59] Durch die Einführung einer dirigierenden Gruppe mit einem nukleophilen oder elektrophilen Charakter wird nach einer vorausgehenden C-H-Amidierung eine anschließende intramolekulare Cyclisierung ermçglicht, die die Bildung von bicyclischen Verbindungen fçrdert (Schema 20). Aufd iese Weise konnten Chinazoline [60] und ihre N-Oxide, [61] Benzimidazolene, [62] Azolopyrimidine [63] und Thiadiazin-1-oxide [64] in einem Syntheseschritt hergestellt werden. Ausd er Verwendung einer elektrophilen dirigierenden Enaminon-Gruppe ergibt sich die Mçglichkeit der Synthese von 4-Chinolonen.…”

Rhodium(III)-catalyzed C–H functionalization of C-alkenyl azoles with sulfoxonium ylides for the synthesis of bridgehead N-fused [5,6]-bicyclic heterocycles

“…The most extensive related research has focused on C–H functionalization of C-aryl azoles for the synthesis of tricyclic and higher order aza-fused heterocycles. 5–13 Dong and co-workers reported the first examples of C–H functionalization for the preparation of ring-junction nitrogen [5,6]-bicyclic heterocycles by annulation of N -alkenyl imidazoles with internal alkynes. 14 More recently, we reported the C–H functionalization of C-alkenyl azoles with various electrophiles, including internal alkynes and diazoketones, for the synthesis of bridgehead N -fused bicyclic heterocycles (Scheme 1A).…”