A new, wide ranging, synthetically powerful, catalytic tandem cyclisation-anion capture process is proposed which depends on the rate of cyclisation of an organopalladium specifies (RPdX) onto a proximate alkene or diene being significantly faster than anion exchange and reductive elimination in the sequence RPdX → RPdY → RY + Pd(0). The catalytic cyclisation - anion capture sequence is illustrated
(and in some cases rhodium) catalysed regiospecific 5-exo-, 6-endo-and 6-exo-trig cyclisations of aryl iodides and vinyl bromides onto proximate alkenes or heteroaromatic rings (indole, pyrrole) lead to a wide variety of fusedring systems. In appropriate cases the methodology provides a facile approach to the creation of tetrasubstituted carbon centres. Double bond isomerisation in the product is only
Carbamoyl Radical‐Mediated Synthesis and Semipinacol Rearrangement of β‐Lactam Diols
作者:Marie Betou、Louise Male、Jonathan W. Steed、Richard S. Grainger
DOI:10.1002/chem.201304982
日期:2014.5.19
ring system, the scope of the tandem 4‐exo‐trig carbamoylradicalcyclization—dithiocarbamategrouptransferreaction to ring‐fused β‐lactams is evaluated. β‐Lactams fused to five‐, six‐, and seven‐membered rings are prepared in good to excellent yield, and with moderate to complete control at the newly formed dithiocarbamate stereocentre. No cyclization is observed with an additional methyl substituent
Stereospecific S N 2? reactions of exo-4-substituted 3-halogenobicylo[3.2.1]oct-2-enes
作者:H. Maskiil、Alan A. Wilson
DOI:10.1039/p29820000039
日期:——
samples of exo-bicyclno[3.2.1]octan-2-ol are obtained from hydrolysis followed by hydrogenation–hydrogenolysis of exo-3,4-dihalogenobicyclo[3.2.1]oct-2-enes. Attempted tosylation of the intermediate hydroxy-halides in these reactions by the Tipson procedure gave only exo-4-chloro-3-halogenobicyclo[3.2.1]oct-2-enes. No inversion of configuration was detected in the reactions of exo-3,4-dihalogenobicyclo[3
的立体化学纯的样品外-bicyclno [3.2.1]辛-2-醇从水解,随后的氢化,氢解得到的外切-3,4-dihalogenobicyclo [3.2.1]辛-2-烯类。在这些反应中,通过Tipson程序尝试甲苯磺酸化中间体羟基卤化物,只能得到外型-4-氯-3-卤代双环[3.2.1]辛-2-烯。在非质子偶极溶剂中,外-3,4-二卤代双环[3,2,1]辛-2-烯与卤化so的反应未检测到构型反转。这些结果得出结论,该系统中的S N 2'反应发生在具有相对构型但绝对构型反转的共价底物上。
The Stereochemistry of the Bicyclo[3.2.1]octane System. III.<sup>1,2</sup> The Addition of Dihalocarbene to Bicyclic Olefins