Note on “the Stereochemical Requirements for Long Range Coupling in α-Halogenocyclohexanones”

✍ Scribed by M. Anteunis; N. Schamp

• Publisher: Wiley (John Wiley & Sons)
• Year: 2010
• Weight: 183 KB
• Volume: 79
• Category: Article
• ISSN: 0037-9646
• DOI: 10.1002/bscb.19700790705

✦ Synopsis

In reply t o the paper of Jefford and Waegell [I] it is shown that non-classical longrange coupling does exist in 3,3,S,5-tetrasubstituted-2-halo-cyclohexanones. Following the reasoning of those authors, an even larger abnormal coupling than originally proposed by us[2] would exist. It is illustrated however that in our original assignation of peaks to axial resp. equatorial H-4 and H-6 hydrogens, we have not used false premises. Therefore our original statements [2] are maintained.

In connection with the preceding paper by C. Jefford and B. Waegell[l], we want to stress some points which seem to us to be essential in the discussion of the pmr pecularities of 2-chloro-, and 2-bromo-3,3,5,5-tetramethylcyclohexanone (ll)*. Our attribution of the pmr signals in CDCI, to the appropriate hydrogen atoms was based [2] on the observation of two long range couplings, which are believed to follow a "classical" planar zig-zag path or M-mode: 1) the 45 coupling between one of the methyl signals with the B-parts of both H-4 and H-6 AB quartets and; 2) a ''large'' 45 coupling between the A parts of both H-4 and H-6 quartets (not shown in fig. l*).