Azeto quinazolines

Ab initio calculations indicate that in the gas phase the reaction of ketene inline and formaldehyde is concerted but asynchronous whereas in dichloromethane it is a two-step zwitterionic reaction.38 The 2 + 2-cycloadditions of keteniminium triflates with imines yields 2-azetidiniminium salts with cis stereoselectivity.39 The intramolecular 2 + 2-cycloaddition of ketenimines with imines (24) provides a novel synthesis of azeto[2,l-Z>]quinazolines (25) (Scheme 9).40... 

The reaction between ketenimines and imines was found to be much more difficult to accomplish [85, 86]. However, Alajarin et al. [87, 88] discovered that the intramolecular version of the reaction proceeded smoothly and several previously unknown azeto[2,l-b] quinazolines (91)] were proposed (Scheme 22). 

The azeto[2,l-4]quinazolines 178 (R = OMe or N02) in solution in chloroform or dichloromethane undergo slow oxidation, which is accelerated by light, to the quinazolines 179 (R = OMe or N02). The quinazolones are obtained more efficiently by oxidation of 178 by activated manganese dioxide <1997T13449>. 

The aza-Wittig reaction and aza-Wittig-type reactions from azaphosphoranes by thermolysis and by the reaction of azides and trimethylphosphine have been used to obtain azeto[2,l- ]quinazolines (Scheme 15) <1998MI1,... 

Although quinazolin-4(3//)-one itself does not undergo photochemical intramolecular [2 + 2] cycloaddition to alkenes, its 2-(trifluoromethyl) analog does perform such a reaction. Thus, irradiation of 2-(trifluoromethyl)quinazolin-4(3i/)-one in methanol under bubbling ethene gives the [2 + 2] cycloadduct, 2a-(trifluoromethyl)-2,2a-dihydro-l/y-azeto[l,2-a]quinazolin-4(377)-one as the sole product. In several cases, the initially formed adduct of 2-(trifluo-romethyl)quinazolin-4(3/7)-one with alkenes is further transformed under the irradiation conditions." ... 

Condensation of 2-azido-P-phenethylamine with 4-chloro- or 4-nitrobenzaldehyde followed by reaction with diphenylketene in refluxing toluene gives the ketenimine 59 which undergoes an intramolecular [2tc + 27t] cyclisation to the azeto[2,l-6][l,3]benzodiazepines 60 <97T13449>. The method may be used also to synthesise azeto[2,l- )]quinazolines, the main thrust of the publication, but the tether cannot be increased further as the respective 8- and 9-membered ring systems could not be formed. UV irradiation of 4,6-diazido-3-methylisoxazolo[4,5-c]pyridine gives two products which have been identified and isoxazolo-... 

TMSK can also react with in situ generated aza-Wittig reagents to furnish azeto[2,l-fc]quinazolines and isoquinolines (eq 20). ... 

An intramolecular cycloaddition reaction involving a ketenimine with two different substituents on its sp carbon terminus 42 affords a mixture of mainly m-azeto[2,lb]-quinazoline 43 and the trans- isomer 44 in total yields of 29-84... 

An intramolecular ketenimin-ketenimine [2+2] cycloaddition reaction has also been observed. The bis-ketenimine 57 was generated in situ by the aza-Wittig reaction and intramolecular cyclization afforded azeto[2,l-b]quinazolines 58 in moderate to good yields." ... 

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