Synthesis and rotational barrier of an unsymmetrical bi-annulenyl derived from a bridged [14]annulene, a model for 1,2′-binaphthyl
                                
                                    
                                        作者:Reginald H. Mitchell、Ji Zhang                                    
                                    
                                        DOI:10.1016/s0040-4039(97)01518-9
                                    
                                    
                                        日期:1997.9
                                    
                                    Nickel(0) catalysed coupling of a 1:1 mixture of 2-bromo- and 4-bromo-trans-10b,10c-dimethyldihydropyrene yields 28% of the first unsymmetrically connected bi-annulenyl 4, with 33% of 2. Unlike 2, the bi-annulenyl 4 has a significant barrier to rotation which is estimated at 11.0 kcal/mole from T-c measurement compared to an MM2+PI calculated barrier of 12 kcal/mole. This is the first measurement of the barrier to rotation in a 1,2'-binaphthyl type system. (C) 1997 Elsevier Science Ltd.