Heteronuclear NMR spectra

Aside from C-H coupling constants (often obtained from satellites in NMR spectra) not very much information is available on the NMR spectra of small heterocycles. A recent review (B-79MI50101) devotes only seven pages to the NMR spectra of all three- and four-membered heterocyclics. 

Azetidine N shifts are similar to those of the aziridines. Unsubstituted azetidine has its N resonance (relative to anhydrous ammonia) at 25.3 p.p.m., and N-r-butylazetidine shows the signal at 52 p.p.m. (80JOC1277). 

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The 31P NMR spectrum of (89) includes a resonance due to the Pd-coordi-nated phosphorus at high field (8 33.92 ppm).418 Detailed 1- and 2-D homo-and heteronuclear NMR spectra, including 1H, 13C, 1H-111 COSY, 1H-I 3C COSY, were reported for trans-PdL2X2, where X = Cl, Br L = 2- or 8-diethylquinolyl methylphosphonates.419 Similar experiments were reported to give full assignments of [Pd(p-K2-OAc)(p-K1-OAc)(KP, KC14-phenop)]2, where... 

Referencing of heteronuclear NMR spectra can be a source of confusion. In an effort to establish universal NMR standards, and hence chemical shift scales, lUPAC have recently adopted a procedure in which aT/NMR spectra are, effectively, referenced to the H signal of TMS. ... 

DFT calculations of H-H and H-C couplings across two and three bonds and a simulation of 2D H homo- and H- C heteronuclear NMR spectra of organic molecules have been suggested by Biffulco et al. as a tool in the determination of the relative configuration of organic compounds. 

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