G.J. van Hummel

Selective functionalization of calix[4]arenes at the upper rim

Methods are described for the selective diametrical functionalization of calix[4]arenes at the upper rim by transfer of functionality and selective substitutions at the para positions of the phenol rings. The crystal structure of 26,28-dimethoxy-11,23-dinitrocalix[4]arene is described.

The tertiary amino effect in heterocyclic synthesis : mechanistic and computational study of the formation of six-membered rings

The mechanism of the ring closure of [2-(1-pyrrolidinyl)phenylmethylene]-propanedinitrile (2a) to l,2,3,3a,4,5-hexahydropyrrolo[1,2-a]quinoline-4,4-dicarbonitrile (3a) has been studied by kinetic measurements using 1H-NMR spectroscopy. It could be shown that the rate-determining step consists of an intramolecular 1,5 hydrogen transfer, which is accompanied by charge separation within the- molecule. The calculated (AM1) and experimental (X-ray) molecular structure of 2a are in fairly good agreement. In the ground state geometry a 1,5 hydrogen transfer will most likely take place suprafacially. Subsequent rotation of the former vinyl group and C-C-bond formation, leading to a six-membered ring, also take place in a stereochemically defined way.

Synthesis of pyrrolizines by intramolecular capture of 1,4-dipolar intermediates in reactions of enamines with dimethyl acetylenedicarboxylate

Solvent polarity and reaction temperature strongly influence the reactions of dimethyl acetylenedicar-boxylate (DMAD) with 1-pyrrolidinyl enamines of acyclic and cyclic ketones. Whereas DMAD and 1-[1-phenyl-2-(phenylthio)ethenyl]pyrrolidine (3) give only a mixture of the isomeric 1,3-butadienes (5) in apolar solvents, in methanol the main product is the pyrrolizine 7, together with 5. Again in methanol, DMAD reacts at 0-5° with 8, 9 and 10 to give exclusively 1:1 adducts, the pyrrolizines 11,12 and 13, respectively, whereas at −50° 8 and 9 give 1:2 (enamine : DMAD) adducts, the pyrrolizines 14 and 15, respectively; a single crystal X-ray analysis of 14 gave the structure of the 1:2 adducts. In the same solvent methyl propiolate and 8 give only the linear Michael adduct 17. The enamine-ketone 18 reacts with DMAD in propylene carbonate at 0–5° to give, via (2 + 2)-cycloaddition and ring expansion, 19, and the linear Michael adduct 20. The mechanism of (2 + 2)-cycloaddition and pyrrolizine formation is discussed in terms of a common tied-ion pair intermediate formed in the first, rate-determining step, followed by a second solvent-dependent step.

.alpha.-Selenocarbenium ions: preparation, x-ray molecular structure determination, and proton and carbon-13 NMR spectral characterization

Les sels des ions bis-methylselenocarbenium RC + (SeMe) 2 Y − (R=H 1 Et, PhCH 2 ; Y=BF 4 , SbCl 6 ) ainsi que leurs analogues bis-methylthio sont prepares par reaction des triseleno- et trithioorthoesters soit avec lion tritylium soit avec un sel dargent approprie dans le dichloromethane

Novel applications of the “t-amino effect” in heterocyclic chemistry; synthesis of 1-alkylindoles

Thermal rearrangerment of 2-vinyl-1-(1-pyrrolidinyl)benzenes varies with the leaving group ability of substituents in the vinyl moiety; compound 3 having an OR group 9-(alkoxy-methyl)pyrrolo[1,2-a]indoles and compounds 6 (X = OAc, OTs or Cl) yield 1-alkylindoles.

The structures of anhydrous 1,5- and 2,6-diazanaphthalene

Both molecules have the formula C 8H6 N 2. 1,5Diazanaphthalene: tetragonal, P41,32~2 (P4!2~2 was chosen), a = b = 7.4079 (3), c = 24.089 (2) A, Z = 8, V = 1321.9 (1)/~3, Dx = 1.308 g cm -3, weighted R = 0.041,/~(Mo/Ca) = 0.76 cm-L 2,6-Diazanaphthalene: monoclinic, P2Jc , a = 4.8281 (4), b = 5.5254 (3), c = 12.0834 (8) A, fl = 94.28 (2) ° , Z = 2, V = 321.46 (4) ,i~3, Dx = 1.345 g cm -3, weighted R = 0.042,/ t(Mo Ka) = 0.78 cm -~. Data collection for both cases was carried out at 20°C. The X-ray proton geometries differ from those previously proposed [Lee & Gilson (1976). Can. J. Chem. 54, 2783-27871 on the basis of NMR experiments. Introduction. In our laboratory, the chemical and physical properties of diazanaphthalenes are studied [e.g. Huiszoon, van Hummel & van den Ham (1977)1. In this paper we report the X-ray analysis of those isomers that can be expected to be centrosymmetric 1,5and 2,6-diazanaphthalene. The dihydrates of these compounds have been investigated earlier by Brufani, Fedeli, GiacomeUo, Riccieri & Vaciago (1966). Our interest in the crystal structures of the anhydrous compounds originates from our objective to compare experimental heats of sublimation of all diazanaphthalenes with heats of sublimation calculated on the basis of intermolecular force fields. Recently, Lee & Gilson (1976) reported an NMR study on the title compounds. From the NMR data and with the aid of the X-ray data of Brufani et al. (1966), these authors proposed proton geometries. These geometries differ from those derived by the present Xray experiment. 1,5and 2,6-diazanaphthalene were prepared following the instructions of Albert (1960) and Danieli & Ricci (1973) respectively. Both compounds were purified by passing them through a column packed with basic alumina. After thorough drying over molecular sieves, the solvent was evaporated and the residual compounds were sublimed in vacuo. The crystals were sealed in Lindemann-glass capillaries. Special dry Table 1. Details o f data collection Number of Scan Scan reflexions Compound 0-range (o) width (o) time (s) measured 1,5-Diazanaphthalene 3.0-25.0 1.50 5

1,4-diacetoxy-β-lactams. Reactions with nucleophiles

β-Lactam reacts with hetero nucleophiles under ring cleavage to give 2,2-dimethyl-3-oximinobutanoic esters 6 and 7 . N-hydroxyazetidine 5 , the precursor of β-lactam 1, is prepared by a new method.

The crystal and molecular structure of 2,7-diazanaphthalene

X-ray diffraction data were collected at 20°C on a computer-controlled Philips diffractometer (PW 1100). The structure was solved by direct methods and refined by the full-matrix least-squares method to an R of 0.065 (weighted R 0.046). The molecule in the crystal is of lower symmetry than C2,.. The geometry of the molecule has been compared with NMR results obtained by Danieli, Lunazzi & Veracini [J. Chem. Soc. Perkin II, (1976), pp. 19-201. As a result a C-H bond-length correction of 0.09 (2) A was found.

Reduction of nitro groups by ynamines; synthesis and x-ray crystal structure of n,n-diethyl-3,3a-dihydro-3-methylbenzofuro[3,2-c]isoxazole-3-carboxamide

3-Nitrobenzo[b]furan and 1-diethylaminopropyne react thermally at 5–10°C to give a 1:1 addition product ( ) in which one of the oxygen atoms of the nitro group is transferred to C-1 of the acetylene. The structure of the benzofuro[3,2-c]isoxazole ( ) has been determined by X-ray crystallography.

N,N'-Tetramethylenedibenzamide (TMDB)

Cl8H20N202, monoclinic, P21/c, a = 5.118(3), b = 5.324(3), c = 28.410 (5) /~, B = 97.05 (5)°, Z = 2. The crystal structure was solved by direct methods. All H atoms have been located. R w = 4.7%. The planes of the phenyl ring and the amide ngroup are rotated with respect to each other due to steric hindrance. Hydrogen bonds connect molecules related by translation in the a direction.