Tuning Stereoselection in Tethered Biginelli Condensations. Synthesis of cis- or trans-1-Oxo- and 1-Iminohexahydropyrrolo[1,2-c]pyrimidines

Stereoselection in tethered Biginelli condensations can be tuned to give either the cis or trans stereoisomer of 1-oxohexahydropyrrolo[1,2-c]pyrimidine and 1-iminohexahydropyrrolo[1,2-c]pyrimidine products (see eq 1). With substrates having urea and N-sulfonylguanidine functionality (Schemes and ),...

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Bibliographic Details
Published in:Journal of organic chemistry 1999-03, Vol.64 (5), p.1520-1528
Main Authors: McDonald, Andrew I, Overman, Larry E
Format: Article
Language:English
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Summary:Stereoselection in tethered Biginelli condensations can be tuned to give either the cis or trans stereoisomer of 1-oxohexahydropyrrolo[1,2-c]pyrimidine and 1-iminohexahydropyrrolo[1,2-c]pyrimidine products (see eq 1). With substrates having urea and N-sulfonylguanidine functionality (Schemes and ), cis stereoselection (4−7:1) is observed when the condensation is accomplished under Knoevenagel conditions, while trans stereoselection (4−20:1) is observed when the condensation is carried out in the presence of polyphosphate ester (PPE). Under both conditions, steroselectivity is highest in the N-sulfonylguanidine series. With substrates bearing a basic guanidine unit, the trans product is formed exclusively under Knoevenagel conditions (Scheme ).
ISSN:0022-3263
1520-6904
DOI:10.1021/jo981972g