Graphical Abstract
Transfer Hydrogenative Cycloaddition. Ruthenium(0) complexes modified by CyJohnPhos or RuPhos catalyze the successive C-C coupling of acetylenic aldehydes with α-ketols to form [4+2] cycloadducts as single diastereomers. This method enables convergent construction of type II polyketide ring systems of the angucycline class.
Two new mesogenic series have been synthesized. They have the same main core which contains four aromatic rings, with two lateral substituents on the same side of one of the inner rings. One of the substituents is a 4-chlorobenzyloxy group and the second is an alkoxy chain. The positions of the lateral substituents are di erent in the two series. Despite the large aromatic branch, an enantiotropic nematic phase is obtained for most of the compounds. The orientational ordering behaviour of these new compounds has been investigated by C-13 NMR, and two isomeric compounds containing a lateral dodecyloxy chain were chosen for the study. The order parameters of the chain were obtained by a 2D C-13 NMR technique with variable angle spinning. The temperature dependence of the order parameters was determined using the C-13 chemical shifts with slow spinning of the sample parallel to the magnetic ® eld. The ® rst methylene fragment in each lateral substituent of each compound has a positive C± H bond order parameter, implying that this fragment adopts a cisconformation in the nematic phase. The two lateral substituents are folded back along the mesogenic core in opposite directions. The lateral chain is found to be roughly aligned along the molecular long axis imposed by the core, whereas the para-axis of the phenyl ring in the lateral aromatic branch makes a considerable angle with the molecular long axis. It was also found that the di erent patterns of substitution do not a ect the position of the molecular long axis to any large extent.
Upon further examination of the NMR spectra for the products of the reduction of the Se-phenyl 1-methoxybicyclo[2.2.2]oct-5-ene-2-carboselenoate 5 f the authors of this Communication have found that the reaction did not give the expected 1-methoxy-bicyclo-[2.2.2]oct-2-ene 6 f in 67 % yield as reported in Table 1 (entry f). Instead, three major products were obtained in a combined yield of 67 %: the expected product 6 f (16 %) along with the two products of cyclopropylcarbinyl radical rearrangement, the endo (major, 57 %) and the exo (minor, 27 %) isomers of 2-methoxybicyclo[3.2.1]oct-6-ene, the former being a known compound. [1] [1] a) M. A. Battiste, J. M. Coxon, A.
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