Synthesis of 2‐oxo‐Δ²‐Pyrrolino‐[1,2‐a]‐(4H)‐Perimidine by N,C‐cyclo‐condensation to A heterocyclic ketene AMINAL

Abstract

2-Substituted (1 H)-perimidine 1 reacts with various 2-chloroacyl chlorides 3 to afford new ethyl 2-0x0-A2pyrrolino-[l,2-a]-(4H)-perimidine-3-carboxylates 5 in good yields by a N,C-cyclocondensation reaction sequence. The H, 3C NMR spectrum of some representative compounds are discussed. The reactions of 1 with trans-cinnamoyl chloride 6 and with 3-chloropropanoyl chloride 8 as P-dielectrophiles have been investigated and gave directly the corresponding fused perimidines 7 with reverse regiochemistry. Ethyl 4-methyl-3-0x0 -2(3H)-perimidinylidenepentanoate (2b) : (R = iPr), reaction time = 40 h, Rf = 0.84 (CH2C12), yield = 78%, mp = 154-155"C, MS (m/z) : 324.1494 found (calculated for ClgH20N203 : 324.1474),3H, J =7.1 Hz) ; 3.60 (m, l H , J = 6.7 Hz) ; 4.28 (q, 2H, J = 7.1 Hz) ; 6.4 (d, l H , J = 6.7 Hz, Ar) ; 6.46 (d, l H , J = 6.9 Hz, Ar) ; 7.09 (m, 4H, Ar) ; 11.9 (broad s, lH, NH) ;