... Tetrahedron. Volume 40, Issue 9, 1984, Pages 1487-1490. Cover image. ... Download full text in PDF. Tetrahedron Vol 40, No. 9, pp. ... Formation of either _3 or 4^ should shift upfield the signal of ^ by about 40 ppm,6 while the methyl signal of 1_ should show a large downfield shift. ...