J‐modulated ¹⁹F‐ and ¹H‐detected dual‐optimized inverted ¹J_CC 1,n‐ADEQUATE: A universal ADEQUATE experiment

Abstract

The recently reported 19F‐detected dual‐optimized inverted 1JCC 1,n‐ADEQUATE experiment and the previously reported 1H‐detected version have been modified to incorporate J‐modulation, making it feasible to acquire all 1,1‐ and 1,n‐ADEQUATE correlations as well as 1JCC and nJCC homonuclear scalar couplings in a single experiment. The experiments are demonstrated using N,N‐dimethylamino‐2,5,6‐trifluoro‐3,4‐phthalonitrile and N,N‐dimethylamino‐3,4‐phthalonitrile.

Unequivocal identification of two-bond heteronuclear correlations in natural products at nanomole scale by i-HMBC

“…Thus, we propose the use of i-HMBC as a complement to HMBC for NMR structure elucidation because it provides important isotope shift information at minimal extra cost of total experiment time (also note that if a decreased S/N caused by relaxation was a concern, then the FID could be simply truncated during spectral processing to generate a nominal HMBC spectrum). In addition, methodology for measuring relative 1-n ∆ 1 H( 13/12 C) and 2-n ∆ 1 H( 13/12 C) isotope shifts developed in this work could also be utilized with other heteronuclear NMR experiments, such as HSQMBC, HMQC (D-i-HMBC) and ADEQUATE 60 . Broader adoption of this methodology should lead to more published ∆ 1 H( 13/12 C) isotope shift data, which, in turn, will undoubtedly enhance the body of knowledge for this fundamental yet thus far underexplored measurable NMR parameter.…”