Quinazoline Synthesis by Pericyclic Reactions

After Rossi's synthesis of quinazolines via 6n-electrocyclization (see Scheme 2), a few but unique quinazoline synthesis by electrocyclization were reported [202,203]. On the other hand, rapid analogue synthetic methods of substituted 1,2,3-triazolo[1,5-a]quinazolines based on cycloaddition/condensation of 2-azidobenzoic acid or related compounds were developed by


heat to boil Iii'

C0CH3 17-38%

69 70 CHs

Tennant [204], Smalley et al. [205], and Jones et al. [206]. For example, 1,2,3-triazolo[1,5-a]quinazolines 70 were obtained in moderate yields by base-catalyzed cycloaddition/condensation reaction (Scheme 14) [205]. Synthesis of 4(3ff)-quinazolinones and -imines via 1,3-dipolar cycloaddition has been reported also [207,208]. Novel formation of quinazolines via thermal ring contraction of 3ff-1,4-benzodiazepines is found by Sashida et al. [209]. Synthesis of quinazoline alkaloids by cycloadditions is discussed in Sect. 3.

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