The Structure of Orcylaldehyde As Prepared from Orcinol via the Gattermann Reaction.
MetadataShow full item record
The synthesis of the derivatives of Psoralen, a furocoumarin, has been an area of interest in research at Kalamazoo College for several years. The Psoralen (III) below can be synthesized from B-orcylaldehyde. Orcylaldehyde is obtained through the formylation of Orcinol (IV) via the Gattermann reaction. 2 Crawford prepared this compound, mp, 181-181.5°,s As seen below, however, two theoretically possible isomers result from the formylation. Note that BThe position of the aldehyde group in the formylated orcinol must be determined in the elucidation of the structure of consequently synthesized furocoumarins. On the nuclear magnetic resonance spectrum Crawford claimed that y-orcylaldehyde (II) would possibly display a single peak with its two "equivalent" aromatic protons. s This need not be expected, however, as hydrogen bonding between the aldehyde and hydroxy groups (fig. 2a) may result in different magnetic environments for the two aromatic protons. B- orcylaldehyde with its two non-equivalent protons would be expected to show a pair of distorted doublets (fig. 2b). A portion of the NMR spectrum of the formylated orcinol prepared by Crawford appears in fig. 3a for the aromatic protons. To eliminate the possibility of hydrogen bonding, Whittlesey methylated the formylated orcinol prepared by Crawford with methyl iodide. She obtained both the monomethyl ether (VI), mp. 62.5-63°, and the dimethyl ether (VII), mp. 64.5-65°, of the formylated orcinol. 4 Both products displayed sharp sin&hrts for their aromatic protons on the NMR spectrum in deuterated chloroform, CDCls (fig. 3b). The singlet in fig. 3b suggests that the aromatic protons are equivalent, and that the formylated orcinol has the v-symmetrical structure (II). (Thus the monomethyl and dimethyl ethers would not be structures (VI) and (VII), but (VIII) and (IX)). The structures in the literature whose melting points correspond with the orcylaldehyde and monomethyl and dimethyl ethers prepared by Crawford and Whittlesey all have the B-(1:2:4) structure (I). This project then is to determine whether the formylated orcinol has the B-(1:2:4) structure or the y-(L:2:6) structure.