Synthesis of polycyclic fused [1,2-a]pyrroles

Pyrrolo[1,2-a]quinoxalines based on pyrroles (Review)

“…An example of a synthesis using such an approach is the intramolecular cyclization of 1-(2-isocyano-phenyl)pyrrole (1a), which is easily obtained by dehydration of the corresponding formylamino derivative with . i 1 a R = H, b R = Me; 3 a-e R 2 = H, a R 1 = Et, b R 1 = 2-Pr, c R 1 = CMe 2 Et, d R 1 = Ph, е R 1 = 2-furyl; f R 1 = R 2 = Me; g R 1 +R 2 = (CH 2 ) 6 ; h R 1 = Ph, R 2 = Me; i R 1 = Me, R 2 = CO 2 Et; j R 1 = Me, R 2 = (CH 2 ) 2 CO 2 Et; 4 a R = R 2 = H, R 1 = R 3 = Me; b R = R 2 = H, R 1 = Me, R 3 = Et; c R = H, R 1 = R 2 = Me, R 3 = Et, d R = R 2 = H, R 1 = vinyl, R 3 = Et, e R = R 2 = H, R 1 = Ph, R 3 = Me; f R = R 1 = Me, R 2 = H, R 3 = Et; 9 a R = R 1 = R 2 = H, R 3 = Me; b R = R 1 = R 2 = H, R 3 = Ph; c R = R 3 = H, R 1 +R 2 = (CH 2 ) 4 ; d R = R 1 = R 2 = H; R 3 = (CH 2 ) 2 CH=CH 2 ; e R = Me, R 1 +R 2 = (CH 2 ) 4 , R 3 = H; 10 a R = H, b R = Me a POCl 3 /Et 3 N mixture in THF. The reaction takes place in the presence of catalytic amounts of boron trifluoride etherate under mild conditions (CH 2 CH 2 , 0°C), resulting in the formation of unsubstituted pyrrolo[1,2-a]quinoxaline (2) with an almost quantitative yield [2,3].…”

“…During the construction of the pyrazine ring of the pyrrolo[1,2-a]quinoxaline system the direct source of the N-C fragment can be not only an isocyano function (-N + ≡C − ) but also an acylamino function (-NHC(O)R) [3,[5][6][7][8][9][10]. As a result as far back as 1966 a general method was proposed for the production of pyrrolo[1,2-a]quinoxalines [5] by the cyclization of 1-(2-aminophenyl)pyrroles, obtained by the Clauson-Kaas reaction [11], and their derivatives 18.…”

“…As a result as far back as 1966 a general method was proposed for the production of pyrrolo[1,2-a]quinoxalines [5] by the cyclization of 1-(2-aminophenyl)pyrroles, obtained by the Clauson-Kaas reaction [11], and their derivatives 18. It was unexpectedly found [6] that o-(pyrrol-1-yl)benzophenone oxime 20, which undergoes a Beckmann rearrangement to 5-chloro-2-(pyrrol-1-yl)benzanilide (18e) during the action POCl 3 in DMF, can serve as a starting material for the production of the pyrroloquinoxaline 19e. The structure of the pyrroloquinoxaline 19e was confirmed unambiguously not only spectrally but also by an alternative synthesis from the authentic 5-chloro-2-(pyrrol-1-yl)benzanilide (18e) by the method in [5].…”

“…61 a А = (СН 2 ) 5 , b A = (СН 2 )6 Cyclization in a basic medium also takes place in the case of the reaction of benzaldehyde with derivative of 1-(2-aminophenyl)pyrrole. For example, treatment of the aminoester 28g with an equimolar amount of benzaldehyde in pyridine gives 4,5-dihydropyrrolo[1,2-a]quinoxaline 64 and not the expected pyrrolobenzotriazocine 63[37].…”

Pyrrolo[1,2-a]quinazolines: synthesis and biological properties

“…[18][19][20][21][22][23][24][25][26][27][28][29][30] Noticing the availability of the 2-aminobenzophenones in the synthesis of certain heterocycles, Garcia et al 24 extended these studies to pyrrole and pyrrolo-fused derivatives. Thus, starting from …”