Cisoid couplings

Following this pattern, 3JCC couplings of transoid carbon atoms in aromatic compounds are larger than those in a cisoid coupling path [129]. 

Three-bond carbon-mercury couplings are larger for transoid in comparison to cisoid coupling routes, as shown for the endo-exo pair of 2-norbornylmercury acetate, and met a... 

The electronic structure of 4 (and the other o-quinonoid heterocycles 1,2, and 3) has been discussed in the light of NMR data. For a series of hydrocarbons containing formally cisoid butadiene fragments (10 R and R not explicitly stated), the ratio of the vicinal coupling constants s.e)... 

Three-bond carbon-phosphorus couplings JCP depend on configuration, as expected, transoid couplings being larger than cisoid ones, as demonstrated for cyclohexyl- and 2-norbornylphosphonates in Table 4.52. The Karplus relation (4.13) can be derived from the data for 2-norbornyl derivatives [376]. 

In inter alia the t-butyl substituted compound 118, the cisoid allylic couplings constants to H, 2.3 Hz and that to H", 1.9 Hz together with the transoid counterparts to H, 2.6 Hz and to H", 2.4 Hz indicated a slight variation of the coupling constant with substituent electronegativity In 119 the cisoid and transoid coupling constants were 2.4 and 2.8 Hz... 

Attempts to bring about the acyloin coupling reaction with the diester (31) were unsuccessful. The failure can be attributed to the severe nonbonded interactions between the two ester groups in the cisoid conformation required for coupling to occur. 

Figure 12.16. Dependence of allylic coupling constants on stereochemistry. Solid lines Transoid (Jbx) dashed lines Cisoid Ja - 0 is the... 

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