Stoichiometric cyclotrimerisation of chiral alkynes at a ruthenium centre: preparation of optically active (η6-arene)(η4-cycloocta-1,5-diene)ruthenium(0) complexes
                                
                                    
                                        作者:Paolo Pertici、Alessandra Verrazzani、Emanuela Pitzalis、Anna Maria Caporusso、Giovanni Vitulli                                    
                                    
                                        DOI:10.1016/s0022-328x(00)00881-0
                                    
                                    
                                        日期:2001.3
                                    
                                    The chiral alkynes (S)-MeCH(R)-C drop CH. 2 (R = Et, 3-methyl-1-pentyne, a; 'Pr, 3,4-dimethyl-1-pentyne, b;'Bu, 3,4,4-trimethyl-1-pentyne, c), containing a stereogenic centre in alpha position to the triple bond, react at room temperature with the complex Ru(eta (6)-naphthalene)(eta (4)-COD). 1. to give the corresponding optically active complexes Ru (eta (6)-(S)-1, 3, 5-C6H3[CH(Me)R](3)} (eta (4)-COD), 6, and Ru(eta (6)-(S)-1,2,4-C6H3[CH(Me)R](3)}(eta (4)-COD), 7. the eta (6)-1.3.5-arene regioisomer being the prevalent product. With (S)-2a, a mixture of 6a and 7a (6a/7a = 90:10) is obtained and, with the more sterically demanding alkynes (S)-2b and (S)-2c, the regioselectivity to the corresponding complexes 6b and 6c is almost complete. This synthetic procedure does not involve the stereogenic centres on the alkynes and it proceeds with complete stereoselectivity. (C) 2001 Elsevier Science B.V. All rights reserved.