Crystal structure of 1:1 complex crystal between 4-(3-methoxybenzyloxy)-6-methyl-2-pyrone and maleimide.

molecules are one of the important current topics because of unusual and interesting results.1,2 We have reported the solidstate [2+2]photocycloaddition reactions of 1:1 complex crystals between 2-pyrone derivatives and maleimide (2) to afford highly stereoselective cycloadducts.2 As a part of our continuing program, 1:1 complex crystal formation between 4(3-methoxybenzyloxy)-6-methyl-2-pyrone (1) and 2 was investigated. Compound 1 was prepared by dehydrochlorination reaction between 4-hydroxy-6-methyl-2-pyrone and 3-methoxybenzyl chloride with 1,8-diazabicyclo[5.4.0]undec-7-ene in 30% yield according to the previous report.2 1:1 Complex crystal (1·2) (Fig. 1) was prepared as follows. An equimolar mixture of 1 (25 mg, mp 81 – 83 ̊C) and 2 (10 mg, mp 92 – 94 ̊C) was dissolved in 2 ml of hot acetonitrile. The solution was allowed to cool at room temperature, during which fine colorless crystals were formed. After crystallizing overnight, the crystal material was collected by filtration, then dried in vacuo to give colorless plates (mp 89 – 91 ̊C). An X-ray diffraction study of the crystal was carried out to determine the structure. Data collections were performed at 93 K with graphite monochromated Mo Kα radiation on a Rigaku RAXIS-RAPID Imaging Plate diffractometer (λ = 0.71069 Å). The linear absorption coefficient, μ, for Mo-Kα radiation is 1.02 cm–1. A symmetry-related absorption correction using program ABSCOR3 was applied; this resulted in transmission factors ranging from 0.44 to 0.99. The data were corrected for Lorentz and polarization effects. The structure was solved by direct methods using SHELXS-97.4 The structure was refined by a full-matrix least-squares method. The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined isotropically. All calculations were performed using teXsan5 crystallographic software package. Table 1 gives the crystal data and experimental conditions. Figure 2 is an ORTEP diagram of the molecule, which shows the atomic-labeling scheme. The final positional parameters are given in Table 2, and selected bond lengths and angles are listed in Table 3. An X-ray diffraction study shows that the crystal contains 965 ANALYTICAL SCIENCES AUGUST 2002, VOL. 18 2002 © The Japan Society for Analytical Chemistry