Hydroxy group interactions in stannylated carbohydrates. Structures and thermal stabilities of 5-deoxy-5-C-(Ph3Sn)-1,2-O-isopropylidene-α-D-xylofuranose, 5-deoxy-5-C-(IPh2Sn)-1,2-O-isopropylidene-α-D- and -L-xylofuranose, and 5-deoxy-5-C-(I2PhSn)-1,2-O-isopropylidene-α-D- and -L-xylofuranose

Abstract

Structures and thermal stabilities of 5-deoxy-5-C-(Ph₃Sn)-1,2-O-isopropylidene-α-D-xylofuranose, [(D)-3], 5-deoxy-5-C-(IPh₂Sn)-1,2-O-isopropylidene-α-D- and -L-xylofuranose, [(D)-4 and (L)-4], and 5-deoxy-5-C-(I₂PhSn)-1,2-O-isopropylidene-α-D- and -L-xylofuranose, [(D)-5 and (L)-5], are reported. The hydroxy groups in the stannylated xylofuranose derivatives, 3–5, exhibit roles as Lewis bases, Brønsted acids and hydrogen bonding centres. The 5-deoxy-1,2-O-isopropylidene-α-D- and –L-xylofuran-5-yl ligands operate as C⁵,O⁴ chelating ligands (4-membered chelate rings) in 3, C⁵,O³ chelating ligands in 4 (molecule 2) and 5 (5-membered chelate rings), and a C⁵,O⁴,O³ tridentate ligand in 4 (molecule 1) [both 4- and 5-membered chelate rings]. Compounds 4, in contrast to 3 and 5, undergo slow proton-dephenylation reactions in chloroform solutions at ambient temperature. All decompose on heating at 145–155 °C with evolution of PhH, Me₂CO and H₂O. The trigonal bipyramidal tin centres in (D)-5 and (L)-5 are chiral, at least in the solid state. Different modes of O–H–O bonding are found in 3, 4 (molecule 2) and 5 compared to that in 4 (molecule 1).