Pyrrolo quinazolines synthesis

It should be also noted that, in a very recent publication, Liu and coworkers were successful in applying microwave radiation within their domino approach towards the synthesis of pyrrolo[2,l-fc]quinazoline alkaloids such as deoxyvasicinone, 8-hy-droxydeoxyvasicinone, mackinazolinone and isaindigotone, which exhibit a promising broad spectrum of biological activities. In the case of isaindigotone, the authors were able to extend their strategy to a three-component procedure, which comprises the domino conversion of anthranilic acids and Boc-protected amino acids into the tricyclic core skeleton [43]. 

This method has been applied to a large-scale preparation of 6-bromoindole, which reacts with various arylboronic acids via the Suzuki reaction to afford 6-arylindoles (Eq. 10.50).64 6-Bromo-5-methoxyindole for use in the synthesis of marine bromoindole65 and 5-amino-7-ethoxycarbonylindole for use in synthesis of l//-pyrrolo[3,2-g]quinazoline ring system (Eq. 10.51)66 have been prepared from the appropriate o-nitrotoluene. 

Nitrogen Heterocycles.- Reactions of iminophosphoranes have been used to prepare a wide range of heterocycles. Examples of compounds prepared by intramolecular aza-Wittig reactions include 3,4-dihydroquinazolines (191) and quinazolines (192), quinazoline derivatives (e.g. 193),pyrrolo( 1,2-a)quinoxalines (194), indolo[3,2-clquinolines (195), and indolo[l,2-c]quinazolines (196),"8 imidazolinones (197),"9 quinazolinones (198),"9, 120 pyrido[2,3-d]pyrimidine derivatives (199), 21 and 4,5-dihydropyrazolo(3,4-d]pyrimidine derivatives (200). 22 Tributyl(cyclohepta-1,3,5-trienylimino)phosphorane (201), prepared by thermal isomerization of the 2,4,6-derivative, reacts with a,p-unsaturated ketones to give 9H-cyclohepta[b]pyridine derivatives (202). 23 a synthesis of (2,4)pyridinophanes (204) by the reaction of N-vinyliminophosphoranes (203) with a,P-unsaturated ketones has been reported. 24... 

Denny and co-workers used a two-step sequence to prepzire 4-thiomethyl substituted quinazolines as versatile intermediates for the synthesis diversely substituted quinazolines. Treatment of 6-methyl-6//-pyrrolo[2,3-g]-quinazoline with Lawesson s reagent, followed by methylation using methyl iodide under basic conditions, gave the corresponding quinazoline in 32% yield over two steps. 

Strategy has also been used for the synthesis of optically active pyrrolo[2,l- ]-quinazoline alkaloid, (5)-(-)-vasicinone (152) Fortunately, by this synthesis the authors have clarified that natural L-vasicinone has the ( S)-configuration. After 0-TBDMS (0-tcrf-butyl-dimethylsilyl) protection, o-azidobenzoylation followed by treatment of compound 149 (R = OTBDMS) with tributylphosphine afforded (5)-(-)-vasicinone (152) via the tandem Staudinger/intramolecular aza-Witlig reaction followed by TBDMS deprotection of 151 (Scheme 15.34). 

Molina P, Alajarin M, Vidal A (1990) New methodology for the preparation of pyrrole and indole derivatives via iminophosphoranes synthesis of pyrrolo[l,2-fl]quinoxalines, indolo[3,2-c] quinolines and indolo[l,2-c]quinazolines. Tetrahedron 46(3) 1063-1078. doi 10.1016/80040-4020(01)81384-3... 

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