J. Indian Chern. Soc., Vol. 88, October 2011, pp. 1577-1580 Synthesis of 8,8'-(polymethylene-/o-xylyl-dioxy)di(pyrano[4,3-b]-1-benzopyran- 10H-10-one) and its conversion to corresponding diacrolein derivative Suman Kalyan Panja, Sourav Maiti and Chandrakanta Bandyopadhyay* Department of Chemistry, Ramakrishna Mission Vivekananda Centenary College, Rahara, Kolkata-700 118, India E-mail : kantachandra@rediffmail.com Manuscript received 29 November 2010, accepted 21 March 2011 Abstract : 6,6'-Tethered-di(4-oxo-4H-1-benzopyran-3-carboxaldehyde) undergoes inverse electron demand [4+ 2] cycload- dition reaction with ethoxyethene to produce endo-di{pyrano[4,3-b]-1-benzopyran), which produces diacrolein when treated with NaOMe in methanol. Keywords : 3-Formylchromone, benzopyran, Diels-Aider reaction. Introduction Most of the dichromones appeared in the literature are pharmaceutically important 1 . Disodium cromoglycate (1) acts as an antiasthmatic and antiallergic compound, its binding activity to human serum albumin was deter- mined2. A khellin like 7, 7' -glycerol-briged dichromone 2 exhibits antianaphylactic activity. In passive cutaneous anaphylaxis testing, compound 2 was found to be more effective at low dose than 1 3 . Dichromones isolated from Selaginella delicatula exhibit antitumar activity 4 . the synthesis of 6,6' -(polymethylenedioxy)di(chromone- 3-carbaldehyde) 7 . In continuation to our interest in synthesising various dichromones 8 , we report herein the synthesis of di(pyrano[4,3-b]-1-benzopyran) and its de- composition9 to diacrolein. Results and discussion A solution of 3 in dichloromethane was heated under reflux for 20 h in the presence of excess ethyl vinyl ether (EVE). Solvent and excess EVE was distilled out from 8 S OMe OMe O-CH 2 -C(H-CHr0 ' <XNO O.CH CH-CH OH - I I r, 2 I I 0 0 0 0 ,; OH J 1 ·- OMeO 2 0 NaOzC C02Na Fig. 1 Chromone-3-carbaldehyde, which is a very good build- ing block for the synthesis of chromone-Jinked or chromone-fused heterocycles, exhibited itself also as a heterodiene. It undergoes [4+2] cycloaddition by inverse electron demand with activated olefin ethoxyethene 5 to produce pyrano[4,3-b]-1-benzopyran moiety, which has structural resemblance with fungal metabolite fulvic acid 6 . Presence of OH, OMe or OAc group at 6-position of 3- formylchromone exhibited higher endo-selectivity in the above cycloaddition reactions. We have earlier reported the reaction mixture. The concentrate yielded 4 in mode- rate yields (Scheme 1). The structure of the compound was established on the basis of IR, 1 H NMR and mass spectral analysis. Al- though chromone-3-carbaldehyde produced a mixture of exo and endo diastereomers with the later as the predomi- nant product 5 , in the case of di(chromone-3-carboxal- dehyde) a single diastereomer was isolated. The two pos- sible diastereomers 4-endo and 4-exo are shown in Fig. 2. 1577