Pseudoacids, or cyclic oxocarboxylic acids commonly form non-planar, complementary and non-cooperative, dimeric hydrogenbonds. A dehydration resistant arylpyran dipseudoacid, C16H18O6, has been synthesized and characterized. Crystals of trans-4,4,8,8-tetramethyl-3,7-dihydroxy-1,2,3,4,5,6,7,8-octahydro-2,6-dioxaanthracen-1,5-dione occur in the monoclinic system and form linear hydrogen-bonded chains; it has an elevated melting point without decomposition at 574.6 K. (C) 2007 Elsevier B.V. All rights reserved.
Synthesis of a Bis(boronate) Compound Having<i>s</i>-Indacene Framework and Its Property as a Host Molecule for Dimethylaminopyridine
A bis(boronate) compound (1) in which boronate components are situated on the same side of the planar s-indacene framework is synthesized from 1,5-dihydro-1,1,5,5-tetramethyl-s-indacene by OsO4-catalyzed dihydroxylation in the presence of dihydroxyphenylborane. The property of 1 as a host molecule has been examined with various compounds. The host 1 forms a 1 : 1 complex with 4-dimethylaminopyridine (DMAP) when an equimolar amount of DMAP is added; more concave-type complexes (2) are formed than convex-type complexes (3). When excess amounts of DMAP are present, a 1 : DMAP = 1 : 2 complex (4) can be isolated as a single crystal. This complex can be characterized by NMR measurements and X-ray analyses. These analyses indicate that the concave-type complex 2 does not have a bidentate coordination between the two boron–nitrogen atoms as proposed previously, but has a monodentate coordination form.