Approaches to the synthesis of triterpenes. V. An unusual acid-catalysed rearrangement of a β,γ-unsaturated ketone

1978 ◽  
Vol 56 (16) ◽  
pp. 2150-2155 ◽  
Author(s):  
John W. ApSimon ◽  
Satyanand Badripersaud ◽  
Michael L. Post ◽  
Eric J. Gabe

The reaction of 2-keto-1β,4aβ-dimethyl-1α-[2-(3-keto-1,4,4-trimethylcyclohexyl)ethyl]-7-methoxy-1,2,3,4,4a,9-hexahydrophenanthrene 1a and b with p-toluenesulphonic acid in boiling xylene yields the rearranged product, 1,10-dimethyl-2-[2-(3-keto-1,4,4-trimethylcyclohexyl)-ethyl]-7-methoxy-3,4-dihydroanthracene (3). Crystals of 3 are monoclinic, space group P21/c, Z = 4, with a = 7.2684(3), b = 30.942(2), c = 10.5544(7) Å, β = 98.24(1)°. The structure was determined by direct methods from diffractometer data and refined by block-diagonal least-squares to an R of 0.043 for 1810 observed reflections. The molecule exhibits no unusual geometric features, although positional disorder is apparent in the cyclohexanone moiety.A possible route for the formation of 3 from 1a and b is presented.

2014 ◽  
Vol 2014 ◽  
pp. 1-4
Author(s):  
Harbi Tomah Al-Masri

The reaction of N,N-bis(diphenylphosphanyl)naphthylamine C10H7-1-N(PPh2)2 with (C5H10NH)2Cr(CO)4 (1 : 1 molar ratio) in dichloromethane afforded cis-[Cr(CO)4{C10H7-1-N(PPh2)2}] (1). This complex was crystallized in the monoclinic space group P21/n. The structure was solved by direct methods and refined by full-matrix least squares techniques to an R factor of 0.0313 for 6488 observed reflections. The Cr-metal is coordinated by four terminal CO molecules and a P,P′-bidentate N,N-bis(diphenylphosphanyl)naphthylamine ligand in a distorted octahedral array. The N-atom adopts a planar geometry with the two P-atoms and C-atom attached to it. The four-membered metallacycle ring P2CrN is nearly planar.


1978 ◽  
Vol 31 (9) ◽  
pp. 1953 ◽  
Author(s):  
D Taylor

Crystals of the title compound, C18H20Cl2N2O4, are monoclinic, a 14.706(1), b 17.168(1), c 7.269(1) Ǻ, β 92.72(1)°, space group P21/c with Z = 4. The structure was solved from diffractometer data by direct methods. Block-diagonal least-squares refinement converged at R 0.037, Rw 0.045 for 2103 reflections with I ≥ 3σ(I) which had been corrected for absorption (μ 34.0 cm-1). The asymmetric unit is comprised of two independent half-molecules, each molecule being centrosymmetric. The pyridine rings are distorted from planarity, with a maximum deviation of 0.10 Ǻ at the nitrogen atoms, as a consequence of the short intramolecular N...N contacts of 2.476(4) and 2.473(5) Ǻ.


1983 ◽  
Vol 61 (9) ◽  
pp. 2137-2140 ◽  
Author(s):  
Kottayil I. Varughese ◽  
Maria Przybylska ◽  
Kazimir Sestanj ◽  
Francesco Bellini ◽  
Leslie G. Humber

The crystals of C16H14F3NO3S2 belong to the monoclinic space group P21/c with a = 11.577(1), b = 12.404(1), c = 12.366(1) Å, β = 90.01(1)°, and Z = 4. The structure was solved by MULTAN 78. The parameters were refined by block-diagonal least-squares to a final R of 0.047 for 2679 observed reflections. Of particular interest is an intramolecular attractive interaction between the sulfur and oxygen atoms with an [Formula: see text] distance of 2.879(2) Å, in which oxygen appears to act as an electrophile. Intermolecular hydrogen bonds between the hydroxyl and keto groups join the molecules related through a centre of symmetry into dimers.


1982 ◽  
Vol 35 (2) ◽  
pp. 457 ◽  
Author(s):  
RM Carman ◽  
SS Smith ◽  
CHL Kennard ◽  
G Smith ◽  
AH White ◽  
...  

The crystal structures of two γ-lactones of the bicyclo[2,2,2]octane series, endo-3-carboxy-exo-5- iodobicyclo[2,2,2]octane-2,6-carbolactone (2; R = CO2H) and exo-3-methoxycarbonyl-endo-5-acetoxybicyclo[2,2,2] octane-2,6-carbolactone (7b), have been determined by direct methods from three-dimensional X-ray data and refined by least-squares to final residuals of 0.033 (2; R = CO2H) and 0.036 (7b) for 1918 and 630 'observed' reflections respectively. Crystals for (2; R = CO2H) are monoclinic, space group P21/c with Z 8 in a cell of dimensions a 7.192(2), b 23.785(8), c 13.199(5) �, β 105.35(2)�, while (7b) crystallizes in the orthorhombic space group P212121 with Z 4 in a cell of dimensions a 13.347(7), b 11.839(7), c 8.227(11) �.


1990 ◽  
Vol 45 (8) ◽  
pp. 1118-1122 ◽  
Author(s):  
R. J. Schubert ◽  
K.-J. Range

Single crystals of (n-C4H9)4NAu(CN)2 were obtained by crystallization using the temperature decreasing method in a newly developed computer-controlled apparatus. The colourless crystals are monoclinic, space group A2/n, with a = 20.216(2) Å, b = 13.130(1) Å, c = 9.328(1) Å, and β = 109.69(1)°. The measured density is 1.45 g/cm3, which agrees with the calculated density of 1.40 g/cm3 for Ζ = 4. The structure was solved by Direct Methods using 674 independent reflections and refined by least-squares procedures to conventional and weighted R factors of 0.068 and 0.058, respectively. The nearly linear [Au(CN)2]--anions form pseudohexagonal layers, in which they are arranged parallel to each other. The shortest Au—Au distance is 8.05 A. The stacking of the layers produces pseudo-trigonal channels, occupied by the cations. The tetra-n-butylammonium cation has four ordered trans chains with idealized D2d symmetry (4̄2 m).


1983 ◽  
Vol 61 (6) ◽  
pp. 1185-1188 ◽  
Author(s):  
Hans Koenig ◽  
Richard T. Oakley ◽  
A. Wallace Cordes ◽  
Mark C. Noble

The reaction of tetrasulphur dinitride with norbornadiene produces the 1:1 adduct S4N2•C7H8; X-ray crystallographic analysis of this compound reveals that olefin addition cleaves one of the sulphur–sulphur bonds of S4N2, yielding a novel eight-membered C2S4N2 ring. Crystals of S4N2•C7H8 are monoclinic, space group P21/c, a = 6.127(1), b = 17.369(1), c = 9.580(1) Å, β = 106.74(1)°, V = 1003.8(5) Å3Z = 4. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.039. The S—S—N—S—N—S fragment of the C2S4N2 ring is planar to within 0.15 Å. The S—C—C—S unit is folded out of this plane to produce a dihedral angle of 74.5°.


1973 ◽  
Vol 51 (16) ◽  
pp. 2794-2798 ◽  
Author(s):  
George Ferguson ◽  
Colin Alan Fyfe ◽  
Wayne Clifford Marsh

Crystals of the 1:1 adduct of tributylphosphine with p-chlorobenzylidenemalononitrile are monoclinic, a = 13.719(2), b = 12.557(5), c = 14.229(3) Å, β = 110.59(2)°, Z = 4, space group P21/c. The structure was determined with diffractometer data by direct methods and refined by block-diagonal least-squares calculations to R = 0.10 for 1405 observed reflections. The structure is zwitterionic with the positive charge localized on the phosphorus atom and the negative charge mainly on the terminal —C(CN)2 group.


1990 ◽  
Vol 68 (8) ◽  
pp. 1277-1282 ◽  
Author(s):  
Ivor Wharf ◽  
Michel G. Simard ◽  
Henry Lamparski

Tetrakis(p-methylsulphonylphenyl)tin(IV) and tetrakis(p-methylsulphinylphenyl)tin(IV) n-hydrate have been prepared and their spectra (ir 1350–400 cm−1; nmr, 1H, 13C, 119Sn) and X-ray crystal structures are reported. The first compound is monoclinic, space group C2/c, Z = 4, with a = 21.589(6), b = 6.207(3), c = 22.861(11) Å, β = 93.80(3)° (22 °C); the structure was solved by the direct method and refined by full-matrix least squares calculations to R = 0.043 for 2755 observed reflections. It has 2 molecular symmetry with the methyl group and one oxygen atom completely disordered in both CH3S(O2) groups in the asymmetric unit. The second compound is tetragonal, space group P42/n, Z = 2, with a = b = 15.408(6), c = 6.379(2) Å (−100 °C); the structure was solved by the Patterson method and refined by full-matrix least squares calculations to R = 0.060 for 1209 observed reflections. It has [Formula: see text] molecular symmetry with the whole asymmetric unit disordered. Water molecules occupy positions on parallel 42 axes but molecular packing requirements prevent all sites having 100% occupancy giving n ~ 1 for the hydrate. Keywords: Tetra-aryltins, crystal structures, sulphone, sulphoxide, hydrogen-bonding.


1983 ◽  
Vol 36 (11) ◽  
pp. 2333 ◽  
Author(s):  
B Kamenar ◽  
RA Pauptit ◽  
JM Waters

The X-ray crystal structure of 3α,4α:5β,6β-diepoxyandrostan-17-one has been determined. Crystals of the title compound (C19H26O3)are monoclinic, space group P21, with a 9.208(2), b 9.620(4), c 9.312(3) �, β 99.14(2)�, V 814.5 Ǻ3 and Z 2. The structure was solved by direct methods and refined to R 0.039 for 887 observed reflexions. The 3α,4α:5β,6β configuration of the epoxide rings confirms the assignment based on proton n.m.r. studies.


1976 ◽  
Vol 54 (5) ◽  
pp. 738-743 ◽  
Author(s):  
J. Brian Faught

The structure of 1,1-bis(diphenylphosphino)-2,2-dimethylhydrazine, [(C6H5)2P]2NN(CH3)2 has been determined crystallographically. The compound crystallizes from n-heptane in the space group P21/c with a = 8.910(1), b = 9.686(1), c = 27.489(4) Å, and β = 102.94(2)° with four molecules per unit cell. The structure was solved from 2669 independent reflections with I > 3σ(I) and refined by block diagonal least squares methods to R = 0.032 and Rω = 0.048. Each diphenylphosphino group is bonded to the same hydrazine nitrogen and the geometry about this nitrogen is nearly planar. The average dimensions of the structure are P—C = 1.828 ± 0.005, P—N = 1.715 ± 0.014, N—N = 1.451, and N—C = 1.457 ± 0.003 Å, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].


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