Ring-closing metathesis reaction-based synthesis of new classes of polyether macrocyclic systems
作者:Naveen、Srinivasarao Arulananda Babu
DOI:10.1016/j.tet.2015.06.070
日期:2015.10
metathesis (RCM) reactions of suitable substrates having terminal olefins, which are assembled from various linkers and hydroxy benzaldehydes and syntheses of a wide range of 16–30 membered, new crown ether-type polyether, aza-polyether, bis aza-polyether macrocycles and dilactone moiety embedded polyethermacrocycles (macrolides) are reported. After the ring-closure reaction, installation of different functional
Rhodium(II)-Catalyzed Cyclization of Bis(N-tosylhydrazone)s: An Efficient Approach towards Polycyclic Aromatic Compounds
作者:Ying Xia、Zhenxing Liu、Qing Xiao、Peiyuan Qu、Rui Ge、Yan Zhang、Jianbo Wang
DOI:10.1002/anie.201201374
日期:2012.6.4
Ahead of the PAC: Polycyclicaromaticcompounds (PACs) can be easily accessed by the combination of Suzuki–Miyaura cross‐coupling and a [Rh2(OAc)4]‐catalyzed carbene reaction using easily available bis(N‐tosylhydrazone)s as intermediates (see scheme; Ts=4‐toluenesulfonyl).
led then, by oxidative cyclization processes, to the hexahelicenophanes 13, provided that the methylenedioxy chain of 12 is long enough (n = 8, 10). As competitive photoreaction, a twofold [2π+2π] cyclodimerization occurred, which furnished the belt cyclophanes 14. The latter process is the only photoreaction for 12 with n=6. The hexahelicenophanes 13 have lower racemization barriers and longer spinlattice
A series of copper(II) complexes (1–9 and 3′) derived from bis-dipyrrin ligands (L1–L9 and L3′) with diverse spacer lengths [–(CH2)n–] have been described. Structural diversities in these complexes have been explicitly established by spectral and structural studies on these and a closely related nickel(II) complex (3′′). All the ligands and complexes have been thoroughly characterized by spectroscopic
A drastic increase in the rate of racemization is found for the bridged hexahelicenophanes 1 (n=8, 10) relative to the unsubstituted parent [6]helicene. This unexpected result occurs from steric interactions between the polymethylenedioxy chains and the terminal rings, which causes the energy of the ground state to be raised and that of the transition state to be lowered.