Joseph J. McKendrick

4-(4-Hy­droxy­phenyl)-2,2,4-trimethyl-7,8-benzo­thia­chroman, a fused-ring counterpart of thia-Dianin's compound

In the title compound, both independent molecules possess a very similar proximal conformation, this referring to the juxtaposition of the 4-hydroxyphenyl substituent with respect to the syn-related methyl group.

Synthesis and crystal structures of normethyl analogues of Dianin's compound

As part of a study of inclusion behaviour, chromans (II) and (III) have been prepared, normethyl analogues of the versatile host Dianins compound (I). Compound (II), which lacks the 2-methyl group cis to the p-hydroxyphenyl substituent, retains the ability to form clathrates. Crystals of the carbon tetrachloride clathrate of (II) are trigonal, space group R, with a= 26.936(6), c= 10.796(1)A, and 18 host and 3 guest molecules in the hexagonal unit cell. An X-ray study has shown that the new cavity-shape is markedly different from that of the parent (I). In contrast to (II), the 4-nor-analogue (III) crystallises unsolvated in the tetragonal system, space group P21c, with a= 12.640(2), c= 17.254(4)A, and Z= 8. This structure has infinite chains of molecules linked head-to-tail by O–H ⋯ O hydrogen bonds of length 2.82(1)A.

A synthetic and structural investigation of the role of hydrogen bonding in clathrate formation

A study of molecules related to Dianins compound (I) in which the hydroxy-function is replaced by another group capable of forming hydrogen bonds is described. The amine (II) crystallises with spontaneous resolution, without incorporation of solvent. The thiol (III) shows an interesting duality of behaviour, crystallising unsolvated with spontaneous resolution from cyclohexane, but forming a true clathrate with carbon tetrachloride. This clathrate crystallises in the trigonal space group R , with a= 27.063, c= 12.074 A, with 18 host and 6 guest molecules in the unit cell. The structure was solved by direct methods, and refined to a final R value of 10.4% for 1 475 independent diffractometer data. Near planar hexagons of sulphur atoms, linked by SH ⋯ S hydrogen bonds, form the top and bottom of each closed cage in the clathrate structure.

Alteration of cage geometry by systematic structural modification of a clathrate host molecule

A study of compounds structurally related to the versatile host compound, 4-p-hydroxyphenyl-2,2,4-trimethyl-thiachroman (I) is described. The compounds (II)–(IV) which possess an additional methyl group at the 6-, 7-, or 8-position of (I) have been synthesised and found to exhibit an interesting spectrum of behaviour. The previously described 7-methyl analogue (III) forms spontaneously-resolved unsolvated crystals while (II) and (IV) are new hosts. A single-crystal X-ray investigation of the trigonal crystals of the cyclo-octane clathrate of the 8-methyl analogue (IV), space group R, a= 33.629(9), c= 8.239(3), and Z= 18 (host), has established the formation of a fundamentally new cage-shape. Compound (V) has also been synthesised in the present study, as have analogues (VII) and (VIII) of the host Dianins compound (VI), but in these three cases no inclusion behaviour has been found.

Synthesis and X-ray structural analysis of 4-p-hydroxyphenyl-2,2,4,7tetramethylthiochroman

The title compound has been prepared and its crystal and molecular structure determined by three dimensional X-ray analysis. Crystals are orthorhombic, a= 11.777(1). b= 16.501 (2), c= 8.479(1)A, Z= 4, space group P212121. The structure was solved by a combination of conventional Patterson and direct methods, and refined by least-squares methods to a final R of 0.091, employing 1 136 diffractometer data. The crystal structure possesses infinite chains of molecules linked head-to-tail by OH ⋯ S hydrogen bonds of length 3.34 A. such that no voids are left for solvent inclusion.

Crystal structure of a clathrate formed by a mercapto-analogue of Dianin's compound

An X-ray diffraction analysis of the CCl4 clathrate of the mercapto-host (II) is described; a key feature of the host structure is the linking of the SH groups of six molecules of (II) by SH ⋯ S hydrogen bonds, such that the sulphur atoms form a near-planar hexagon.

Synthesis and clathrate cavity geometry of a 2-nor-analogue of dianin's compound; X-ray crystal structure

A new clathrate host (II), which corresponds to specific removal of one of the geminal methyl groups of Dianins (I), has been synthesised; the resulting fundamental modification of the cavity shape has been elucidated by X-ray methods.

Formation of benzo[b]thiophens and related compounds by a rearrangement involving ring contraction

Substituted 4-(naphthyl- and phenyl-thio)-4-methylpentan-2-ones (I)–(VI) undergo cyclodehydration by polyphosphoric acid at 100 °C to give thiochormens (VII)–(XII) which, under these conditions, rearrange with ring contraction to the corresponding fused thiophens (XIII)–(XVIII).

Variation of inclusion properties by structural modification of a clathrate host

By controlled modification of the structure of the selected clathrate host (I), it is possible to achieve a significant alteration in cavity geometry, accompanied by a striking change in selective clathration properties.