Synthesis of New Ring Systems: Isomeric 1,2,4-Triazolopyrimido [4″,5″:4′,5′]thieno[3′,2′:5,6]pyrido[3,2c]cinnolines and Other Related Systems

Abstract

1 underwent ring closures with formamide and carbon disulphide to afford pyrimidothienopyridocinnaline 2 and its pyrimido-9,11-thione derivative 3, respectively. Treatment of 1 with triethylorthoformate followed by hydrazine hydrate produced 10-amino-11-imino-pyrimido system 5, which in turn reacted with triethylorthoformate, acetic acid, carbon disulphide, and acetylacetone to cyclize into the systems, 1,2,4-triazolo, 2-methyltriazolo, triazolo-2-thione, and 1,2,4-triazepinopyrimido thienopyridocinnolines 6-8, 11, respectively. Similarly, 3-amino-2-carboxamido-thienopyridocinnoline 12 was reacted with triethylorthoformate to give pyrimidothienopyridocinnoline-11-one 13, which was treated with phosphorous oxychloride and then hydrazine hydrate to produce 11-hydrazinopyrimido system 16. Treatment of 16 with triethylorthoformate, acetic anhydride, carbon disulphide, and ethyl chloroformate afforded the systems, 1,2,4-triazolopyrimidothienopyrido-cinnoline derivatives 16-18, 20, respectively.

Applications of alkyl orthoesters as valuable substrates in organic transformations, focusing on reaction media

“…411 In 2015, Pospech and co-workers introduced an intermolecular one-step methoxylation/acetalization reaction of donor- In 1993, Byun and Bittman synthesized (À)-dimethyl 2,3-Obenzylidene-L-tartrate and its enantiomer (488) in 83-91% yields via the reaction of L-tartaric acid (486), benzaldehyde (487), and TMOF (4) by p-TSA (10 mmol) in methanol at room temperature (Scheme 144). 416 In 2013, Geng et al prepared 4,6-O-arylidenated derivatives (493) and orthoesters (494), regioselectively via the protected/ unprotected sugars (489), benzaldehydes (487,490), and TEOF (5) by organocatalysts such as thiourea (491)/squaramide derivatives (492) in anhydrous CH 3 CN at room temperature (Scheme 145). In this procedure the inuence of various parameters, such as the amount and type of aldehyde, catalyst and orthoester, was investigated on the time and yield of reaction.…”

“…The cyclocondensation of 10-amino-7-( p -tolyl)pyrimido[4′′,5′′:4′,5]thieno[3′,2′:5,6]pyrido[3,2- c ]cinnoline-11-imine (615) with TEOF (5) was accomplished in refluxing acetic acid for 5 h to give 7-( p -tolyl)-1,2,4-triazolo[4′′′,3′′′:1′′,6′′]pyrimido[4′′,5′′:4′,5′]thieno[3′,2′:5,6]pyrido[3,2- c ]cinnoline (616) in 70% yield ( Scheme 185 ). 492 …”