By 1H nmr, the predominance of the conformer with a quasi‐axial 6‐methyl group was established for the pyrido[1,2‐a]pyrimidines I‐III. The 13C nmr spectra of I‐III were completely assigned. The conjugative effect of substitution at G‐3 on 1H and 13C chemical shifts of the C‐9 methylene group parallels its effect on reactivity.
ASJC Scopus subject areas
- Organic Chemistry