Alain Thozet

Crystal and molecular structure of two calix[6]arenes:p-Isopropylcalix[6]arene andp-tert-butylcalix[6]arene—benzene(1∶3) complex

The isopropyl derivative crystallizes from a mixture of carbon disulfide and benzene in the orthorhombic system: Space groupP21nb, a=17.420(3),b=17.708(3),c=18.972(3) Å,V=5852(3) Å,Z=4. Thet-butyl derivative crystallizes from benzene, but the crystal is a complex (1∶3), space groupPĪ,a=15,065(5),b=19.103(3),c=13.878(3) Å, α=106.95(2), β=102.72(2), γ=80.61(2),V=3703(2) Å3,Z=2. Refinement led toR=0.185 for 1512 reflections for the isopropyl derivative, a sufficiently high number to establish the conformation of the molecule; for thet-butyl complexR=0.12 for 7340 reflections. Intramolecular hydrogen bonds are given as well as comparison of the conformation of both compounds. Thet-butyl groups and the benzene molecules are disordered but the isopropyl groups are not.

Enantiopure Trioxadecalin Derived Liquid Crystals: Influence of the Nature of the Phenyl Substituent on the Mesogenic Properties

Reaction of pseudo‐glucal 1 with Grignard reagents derived from 1‐bromo‐4‐(trimethylsilyloxy)benzene, 1‐bromo‐4‐methoxybenzene, 1‐bromo‐4‐methoxymethoxybenzene, 1‐bromo‐4‐dimethylaminobenzene, in the presence of a catalytic amount of NiCl2(dppe), gives the corresponding unsaturated β‐C‐aryl glycosides 2. Desilylation and hydrogenation of 2 leads to β‐C‐aryl glycosides 4, which can be used as chiral precursor compounds in the synthesis of chiral liquid crystals. Combination of 4 with arylaldehydes leads to compounds 5–7, whereas reaction with p‐alkoxysubstituted phenylboronic acids gives the trioxaboradecalins 8–11. The mesogenic properties of these compounds are strongly influenced by the nature of the substituent on the phenyl ring in the molecule. †This paper is dedicated to Professor Gérard Descotes on the occasion of his 70th birthday.

Catalytic Hydrogenation of Organic Solids-Basic Problems

Abstract The hydrogenation of organic solid substances like phenols and phenoxides under mild conditions has been studied. It is shown that those reactions take place in the solid state. Because of the lack of fluid phase the classical catalysis processes cannot explain the high conversion ratios obtained; the spillover effect and the existence of mobile hydrogenating species are discussed.

Resolution and absolute configuration of bromofluoroacetic acid

Abstract The resolution of racemic bromofluoroacetic acid (BrFHCCO 2 H) 1 was effected by crystallisation of its diastereoisomeric α-methylbenzylamine salts. The crystal structure of the p salt (+)- 3a {(+)-BrFHCCO 2 H·( R )-(+)-α-methylbenzylamine} was solved by X-ray crystallography and the ( S )-(+)/( R )-(−) absolute configuration was established for 1 . Diastereoisomeric esters 5a and 5b , obtained by addition of bromofluoroacetic acid to enantiomerically pure epoxychroman 4 , were used to determine the enantiomeric excess of 1 by 19 F NMR. Moreover, the diastereoisomerically pure ester 5a , resulting from addition of enantiomerically pure (+)- 1 to 4 , gave single crystals and its X-ray crystal structure corroborated the ( S )-(+)/( R )-(−) absolute configuration of 1 .

Crystal Structure of the 1" 1" 6 Complex between 18-crown-6, Hydroquinone and Water

Hydroquinone forms a 1 : 1 : 6 complex with 18-crown-6 and water. Crystals of this complex are monoclinic, space groupP21/a witha = 14.289(1),b = 7.972(1),c = 11.596(1) Å, β = 97.72(1)°,Z = 2,Dc = 1.22 g cm−3. The hydroquinone and crown ether molecules lie on centres of symmetry with the crown in theD3d conformation. The water molecules act as a bridge between hydroquinone and the crown ether. The structure consists of molecules linked by a 3-dimensional network of hydrogen bonds: the hydroquinone and two water molecules lie roughly in the (001) plane; the crown ether and four water molecules form bipyramidal structures which are stacked in layers alternating with the previous planes.

Solid State Polycondensation of Precursors of Phenolic Resins

Abstract Twelve substances derived from phenol or 4-alkylphenol, six of which are precursors of phenolic resins, have been prepared by condensation of the phenol with paraformaldehyde or by further reaction of one of these with the starting phenol. Two cyclic oligomers belonging to the class of calixarenes or cyclophanes have been isolated and characterized. Single crystals of some precursors have been obtained and their crystalline structures have been determined. The thermal decomposition of precursors of phenolic resins have been investigated. Their solid state behaviour and their relative reactivities in acidic and basic conditions have been evaluated. The obtained substances can be considered as important intermediates. They are both sufficiently stable and highly reactive.

Double partial cone conformation for p-cumylcalix[6]arene·2.5 dimethylformamide

Abstract The crystal structure of p-cumylcalix[6]arene·2.5 dimethylformamide has revealed that the compound exists in the double partial cone conformation. The DMF molecules are bound to the calixarene via hydrogen bonds. The compound crystallizes in the triclinic space group P1 with a = 17.328(3), b = 17.981(3), c = 17.040(3) A, α = 116.56(2), β = 112.42(1), γ = 76.18(2)°, and Dc = 1.165 g cm−3 for Z = 2. Refinement based on 9418 observed reflections led to a final R value of 0.08.

Conformational analysis of the four 3-methyl-isopropylphenol isomers (thymols) by molecular orbital calculations and X-ray crystal structure determinations

Abstract PCILO calculations have been used in a conformational investigation of 3-methyl- x -isopropylphenols (thymol isomers), including a study of the barrier to internal rotation of substituents. The results of the calculations are in good agreement with those available from experimental crystal structure determinations, except for 3-methyl-6-isopropylphenol. For the latter the calculated most stable conformer cannot form a crystal with hexamers bonded by H bonds, as is determined by crystallography. The heights of the barriers to internal rotation of the substituents are compared with the available experimental data and discussed in terms of steric hindrance.

From p-tert-Butyl-Calix[6]Arene to p-tert-Butyl-[16]Meta Cyclophane

Calixarenes are cyclic phenolic oligomers mixing complexation abilities for neutral or ionic guests and a good functionalization flexibility with a high thermal stability. Since the pionnering work of Gutsche [1], they became a promising chemical platform for the building of a new and large family of synthetic receptors [2].

Polar and Chiral Organic Crystals, Striking Reactivity and Selectivity

Abstract Polar reactivity differences have been found on the two faces of a slice cut along a polar axis in a 3-methyl 4-isopropyl phenol crystal. A case of absolute asymetric synthesis is noted during the chlorination of the same compound.