摘要:

The synthesis of five cyclopropanated glycopyranosides,6α,6β,7α,7β, and11capable of providing access to the title ions has been examined. Simmons–Smith methylenation of methyl 4,6-O-benzylidene-2,3-dideoxy-α-D-eryrtro-hex-2-enopyranoside (8α) under carefully controlled conditions gives an excellent yield of the α-D-alloadduct (6α). A homoallyl iodide, 4,6-O-benzylidene-1,2,3-trideoxy-3-C-iodomethyl-D-ribo-hex-1-enopyranose, (9), is also produced and upon methanolysis undergoes ring closure to an equal mixture of α-Dand β-Danomers of6. Methylene insertion into the aglycon of the starting olefin8α occurs giving small amounts of the ethyl hex-2-enopyranoside (10), the cyclopropanated glycoside derived therefrom,11, being also obtained. Methylenation of the β-D-hex-2-enopyranoside,8β, gives a complex mixture containing at least eight substances, although the expected β-D-mannoadduct,7β, is the major product. There is considerable anomerization of8β and of the primary product,7β; thus the anomer7α is also produced. The 3-epimer (14) of the above-mentioned homoallyl iodide (9) is obtained in small yield.The cyclopronated glycosides are very susceptible to prolonged exposure to the Simmons–Smith medium. Particularly in the case of8β the yields of the various products can be optimized by judicious choice of the duration of the reaction.Proton magnetic resonance data for the adducts are presented. The value of the spacingJ34provides a clear basis for determining the configuration of the ring. However anisotropy due to the cyclopropane ring-current causes the equatorial H-1 in the β-D-manno-anomer (7β) to resonate at higher field than H-1 in the α-Danomer7α.

ISSN:0008-4042    

DOI:10.1139/v72-468

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The homoallyl iodide 4,6-O-benzylidene-1,2,3-trideoxy-D-ribo-hex-1-enopyranose,4, is the second major product from Simmons–Smith reaction of methyl 4,6-O-benzylidene-2,3-dideoxy-α-D-erythro-hex-2-enopy-ranoside,6α. The major product is the cyclopropyl glycoside7α, which when treated separately with the Simmons–Smith reagents furnishes an 85% yield of4. The mechanism of this transformation is investigated. It is not simply a Lewis-catalyzed iodinolysis since zinc iodide in a variety of solvents does not convert7α to4. Methylene iodide is essential, as is the organo-zincate complex, operative in Simmons–Smith reactions.The 3-epimer of the homoallyl iodide4,i.e. 4,6-O-benzylidene-1,2,3-trideoxy-D-arbino-hex-1-enopyranose,5, is produced in only 0.9% yield in the methylenation of the anomeric olefinic glycoside,6β. The low yield is attributable to the extensive anomerization experienced by6β itself, and by the primary reaction products. This leads to a plethora of compounds including both epimeric homoallyl iodides4and5.In order to get it all together, the homoallyl iodide4is transformed into its epimer5by an unambiguous synthetic sequence. Some of the intermediates in this sequence are polyfunctional molecules of considerable synthetic potential.The possibility of an alternative route to compound4directly from the olefinic glycoside6α is discussed. Coordination of the methoxyl oxygen of6α to the organo-zincate complex could achieve an ideal SNi transition state in whichis delivered at C-3 with synchronous departure of the methoxyl group. This mechanism, called the "reverse" allylic rearrangement for reasons outlined in the text, is discussed.

ISSN:0008-4042    

DOI:10.1139/v72-469

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The syntheses of three α-cyclopropylcarbonyl compounds of carbohydrate origin,1,2,3, are described. The cyclopropyl carboxaldehyde1was obtained from the corresponding carbinol by manganese dioxide oxidation of the primary alcohol. However, the secondary cyclopropyl alcohol in8did not respond to manganese dioxide and its oxidation (in the tritylated derivative (14), to the cyclopropyl ketone,2, had to be achieved by ruthenium tetroxide. The sequence leading to2(via8) began with ethyl 4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside11, which added methylene to give the α-D-alloconfiguration with the cyclopropane ringsynto the glycosidic ethoxy group. The diastereomeric tritylated cyclopropyl ketone3, possessing the cyclopropyl ringantito the ethoxy group, resulted from cyclopropanation of the αβ-un-saturated ketone,15. In the latter case, the acetoxy group apparently provides greater directing influence to the incoming methylene than does the allylic ethoxy group.

ISSN:0008-4042    

DOI:10.1139/v72-470

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A new method has been developed for determining the heat of combustion of perfluoro aromatic compounds. The basic differences from previous methods are that no auxiliary substance is used and no water is present in the bomb. The combustion of hexafluorobenzene in a platinum lined bomb yields CO2, CF4, and F2. Visual inspection and the material balance indicate that complete combustion is obtained. The value ofobtained by this method is −224.0 ± 2.0 kcal/mol. Recalculation of the result of Coxetal. (1, 2) obtained from combustion of C6F6in mylar bags in the presence of hydrocarbon oil and water leads to

ISSN:0008-4042    

DOI:10.1139/v72-471

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The possible ways in which alkyl rearrangements can occur in cycloalkenyl cations are described. With cyclohexenyl cations, two rearrangements unique to this system are discussed and experimental evidence for both of these is presented. Use is made of the n.m.r. spin saturation transfer technique in one case.In the final part of the paper, we show how, by repeatedly using both rearrangements, it is possible in theory to scramble the relative positions of all of the carbon atoms with respect to both the different positions within a cyclohexenyl cation framework and with respect to the bonding order of consecutive atoms within the framework. In the unsubstituted case, this corresponds to a 360-fold degenerate rearrangement.

ISSN:0008-4042    

DOI:10.1139/v72-472

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The results of a study of the electronic absorption spectrum of cobalt(II) in Li2SO4–DMSO solution, an equimolar NaHSO4–KHSO4melt, a eutectic melt of Li2SO4–Na2SO4–K2SO4, single salt melts of Li2SO4and Na2SO4and a doped single crystal of K2Zn2(SO4)3have been combined with previous results in sulfate media; all the results can be explained in terms of a blue dodecahedral [Co(O2SO2)4]6−species, a pink octahedral [Co(OSO3)6]10−species or an equilibrium mixture of the two.

ISSN:0008-4042    

DOI:10.1139/v72-473

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Laser Raman and infrared vibrational spectra of solutions of NaNO3in deuterium oxide reveal the presence of bothion pairs and solvated nitrate ions. The degree of association has been measured. The concentration quotients are remarkably independent of concentration and almost equal to the thermodynamic association constant, 0.060 ± 0.006 kg mol−1at 25.0 °C. The latter quantity was obtained by an extrapolation procedure, taking account of the activity coefficients. Values are reported for the activity coefficient of the ion pair. Interpretation is also considered in terms of a place-exchange equilibrium involving the solvent. Vibrational assignments are made to the two forms of nitrate ion present. Density, partial molal volume, conductance, and viscosity data are also presented and discussed in terms of the reported constitution.

ISSN:0008-4042    

DOI:10.1139/v72-474

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The structure of 2-(3′-methyl-4′-nitrophenoxy)-1,3-diisopropylbenzene, C19H23NO3, has been determined by X-ray diffraction. The crystals are triclinic,a = 12.422(24),b = 13.180(25),c = 11.241(30) Å, α = 89.99(20), β = 95.81(15), γ = 105.46(12)°,withZ = 4. The intensities of 8153 independent reflections were measured on a four circle diffractometer, of which 3701 were used in the refinement of the structure to give a final least-squares weighted residue of 0.053.The ether oxygen bond angle in each of the two independent molecules is 120°. The two phenyl rings are nearly orthogonal in each case, while the ring containing the electron withdrawing nitro group is conjugated with the ether oxygen atom. The rings show significant deviations from hexagonal symmetry and the nitro-substituted ring is bent away from the other ring.

ISSN:0008-4042    

DOI:10.1139/v72-475

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The structure of 2-(2′,4′-dinitrophenoxy)-1,3,5-tri-t-butylbenzene, C24H32N2O5, has been determined by X-ray diffraction. The crystals are triclinic,a = 12.160(30),b = 10.564(17),c = 10.684(16) Å, α = 119.23(10), β = 96.06(15), γ = 96.55(15)°,withZ = 2. The intensities of 5359 independent reflections were measured on a four circle diffractometer of which 2471 were used in the refinement to give a final least-squares weighted residue of 0.063. The presence of two electron withdrawing groups on one of the phenyl rings increases the conjugation between the ring and the ether oxygen atom to a greater degree than was found in the previous work. The tri-t-butyl-substituted ring is nearly orthogonal to the other ring. The bond angle at the ether oxygen atom is less than the value found earlier but ring distortions are similar.

ISSN:0008-4042    

DOI:10.1139/v72-476

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The structure of 2-(2′-carbomethoxy-4′-nitrophenoxy)-1,3,5-trichlorobenzene, C14H8NO5Cl3, has been determined by X-ray diffraction. The crystals are triclinic,a = 8.862(10),b = 15.164(10),c = 13.028(14) Å, α = 90.35(8), β = 116.28(8), γ = 97.54(8)°,withZ = 4. The intensities of 6417 independent reflections were measured on a four circle diffractometer of which 4526 were used in the refinement to give a final least-squares residue of 0.047. The two independent molecules in the unit cell show a similar conformation to that found in earlier studies of diphenyl ethers, and the conformation appears to be determined partly by steric effects, since conjugation between the nitro-substituted ring and the ether oxygen atoms is less pronounced than found previously.

ISSN:0008-4042    

DOI:10.1139/v72-477

出版商:NRC Research Press    

年代:1972

数据来源: NRC