No abstract

Ring-opening polymerization of x-pentadecalactone (PDL) by tetrahydroborate complexes of rare earth metals, Ln(BH 4 ) 3 (THF) 3 (Ln ¼ La (1), Nd (2), Y (3)), was studied. These complexes showed high activity for PDL polymerization in THF at 60 C. Among the complexes 1-3, the neodymium complex 2 was most active. The obtained poly(PDL) was demonstrated to be hydroxytelechelic by 1 H-NMR and MALDI-TOF MS spectroscopy.Biodegradation of the poly(PDL) in compost at 60 C was investigated, where 18% weight loss of the samples was observed after 280 days.

The synthesis of chiral, nonracemic difluoromethylthio (SCF 2 H) compounds that contain a tetrasubstituted stereogenic center is reported. Racemic α-SCF 2 H-β-ketoallylesters 5 were initially prepared by an electrophilic difluoromethylthiolation of β-ketoallylesters 6, followed by a Pd-catalyzed Tsuji decarboxylative asymmetric allylic alkylation (DAAA) to provide a wide variety of chiral, nonracemic α-allyl-α-SCF 2 H-ketones (4) with high enantiopurity. This strategy can be extended to the enantioselective synthesis of chiral, nonracemic α-allyl-α-trifluoromethylthio(SCF 3 )-ketones (7).

In the doubly interpenetrated metal−organic framework (MOF) structure with cds topology, [Zn 2 (bpeb)-(dhbdc)(fa) 2 ], 1 (where bpeb = trans,trans,trans-1,4-bis[2-(4′pyridyl)ethenyl]benzene, dhbdc = 2,5-dihydroxy-benzene-1,4dicarboxylate, and fa = formate), the adjacent bpeb ligands are aligned in a slip-stacked manner infinitely, and the olefin pairs are aligned in parallel ready to undergo a quantitative photochemical [2 + 2] cycloaddition reaction. The singlecrystal-to-single-crystal (SCSC) photoreaction under UV light yielded a non-interpenetrated [Zn 2 (poly-bppcb)(dhbdc)-(fa) 2 ], 2 (where poly-bppcb = 1,3-(4,4′-bipyridyl)-2-phenylcyclobutane) in which the poly-bppcb polymer comprising cyclobutane rings are nicely integrated into the two-dimensional coordination polymeric sheet formed by [Zn 2 (dhbdc)(fa) 2 ].This organic polymer can be depolymerized back to 1 by heating 2 at 250 °C in a hot air oven for 6 h. The cleavage of cyclobutane rings to bpeb ligands has been attributed to the hydrogen bonding of the two hydroxy groups in the dhbdc ligand. In a similar metal organo-polymeric framework with bdc ligand, the poly-bppcb could not be depolymerized. Thus, this study provided some new insights into the reversible cleavage of cyclobutane polymers. These polymeric materials based on cyclobutane may be environmentally benign as these can be depolymerized to yield easily disposable and degradable monomers.