Catalytic transformations of 1,6-dioxaspiro[4,4]nonanes

Summary In the vapor phase over platinized charcoal at 300–320°, 2-and 3-alkyi-1,6-dioxaspiro[4.4]nonanes undergo the following transformations: isomerization of one of the tetrahydrofuran rings with formation of tetrahydrofuran oxo compounds, decarbonylation of tetrahydrofuran aldehydes, and isomerization of tetrahydrofuran homologs and tetrahydrofuran ketones to give aliphatic ketones and -diketones, respectively.     

Electrolytic ethoxylation of several γ-furylalkanols

Compounds of the 2-ethoxy-1,6-dioxaspiro[4.4]-3-nonene series were obtained during the electrolysis of solutions of primary, secondary, and tertiary-furylalkanols in ethanol as a result of intramolecular alkoxylation. Depending on the conditions, catalytic hydrogenation of the products leads to the formation of 2-ethoxy-1,6-dioxaspiro[4.4]nonanes or 1,6-dioxaspiro [4.4 ]nonanes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1303–1305, October, 1970.     

Researches on furan compounds

This paper gives the results obtained by liquid phase catalytic hydrogenation under pressure, over ruthenium catalysts, of furan aldehydes, ketones, and carboxylic acids. It is shown that the ruthenium catalysts are highly effective for hydrogenating the furan ring, ethylenic double bonds, and the carbonyl group, though they are not selective with respect to them. At room temperature the furan ring is mostly reduced to a tetrahydrofuran one. It is confirmed that compounds containing the 1, 6-dioxaspiro [4, 4]-nonane grouping are formed by hydrogenating furfurylidene aldehydes and ketones, and -furylalkanols.For Part XXX see [15].     

A simple,efficient, two-step synthesis of symmetric 2,7-dialkyl-1,6-dioxaspiro[4.4]nonanes

A two-step synthesis of symmetric 2,7-dialkyl-1,6-dioxaspiro[4.4]nonanes has been achieved by double Michael addition of nitromethane with two moles of enones on Amberlyst A21, followed by in situ reduction with sodium borohydride, then spontaneous spiroketalization of the obtained nitrodiol, by the Nef reaction under acidic conditions, affords the title compounds in good yields.     

Syntheses based on 8-substituted 3-bromoacetyl-3,8-dimethyl-2,7-dioxaspiro[4,4]nonane-1,6-diones

By reaction of 8-substituted 3-bromoacetyl-3,8-dimethyl-2,7-dioxaspiro[4,4]nonane-1,6-diones with thiourea and substituted thioureas under Hansch reaction conditions, we have obtained the novel heterocycles 3-[2′-amino(arylamino)thiazol-4-yl]-3,8-dimethyl-2,7-dioxaspiro[4,4]nonane-1,6-diones. By reacting the above-indicated bromoacetyl spirodilactones with 5-aryl-3-mercapto-1,2,4-triazoles, we obtained 8-substituted 3-(aryl-3,8-dimethyl-1′,2′,4′-triazol-3′-yl)thioacetyl-2,7-dioxaspiro[4,4]nonane-1,6-diones. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 123–129, January, 2006.     

Three-component reaction of 5-aryl-4-(quinoxalin-2-yl)-furan-2,3-diones,acetylenedicarboxylic acid dimethyl ester,and triphenylphosphine

Three-component synthesis from 5-aryl-4-(quinoxalin-2-yl)furan-2,3-diones, acetylenedicarboxylic acid dimethyl ester, and triphenylphosphine afforded methyl esters of 1,6-dioxaspiro[4.4]nona-3,7-diene-4-carboxylic and 4H-furo[3,2-c]pyran-3-carboxylic acids.     

Electrolytic methoxylation of halognofurans

-Halogenofurans are electrolytically methoxylated in two ways in the presence of sulfuric acid electrolyte, methoxyl groups either adding at the 2 and 5 positions in the furan ring or replacing a ring halogen atom. The following are methoxylated: 2-bromo-, 2-iodofuran, 5-chloro-, 5-bromo-, and 5-iodofurfural, ethyl 5-bromopyromucate. Derivatives of 2, 2, 5-trimethoxy-2, 5-dihydrofuran are prepared, giving on hydrolysis-aldehydo- and-ketoacrylic acids.Total anode polarization graphs are obtained in order to study the electrolytic methoxylation reaction mechanism.Furfural and 2-acetylfuran methoxylate, but only after first undergoing conversion to the dimethylacetal [1, 2].Electrolytic methoxylation of furan derivatives using sulfuric acid as electrolyte was first applied to methoxylation of a pyromucic ester, which, as referred to above, is not methylated using ammonium bromide.     

Hydrogen atom transfer methodology for the synthesis of C-22, C-23, and C-25 stereoisomers of cephalostatin north 1 side chain from spirostan sapogenins

A simple synthesis of all eight C-22, C-23, and C-25 diastereoisomers of the cephalostatin north 1 side chain has been accomplished from (25R)-5α-spirostan-3β-ol (tigogenin). The synthesis involves selective hydroxylations at C-23 and C-25 and reductive opening of the 1,6-dioxaspiro[4.5]decane spirostan system to give a conveniently protected 5α-furostan-3β,23,25,26-tetrol. The construction of the required 1,6-dioxaspiro[4.4]nonane system entailed an intramolecular hydrogen abstraction reaction promoted by the C-25 alkoxyl radical as the key step. Acid-catalyzed isomerization of the spiroketal unit suggested that 22R isomers are the thermodynamic products while the 22S isomers are the result of kinetic control. The acid-catalyzed equilibrium between 1,6-dioxaspiro[4.4]nonane and 1,6-dioxaspiro[4.5]decane systems was also studied. In the 1,6-dioxaspiro[4.4]nonane units, the observed ³J_23,24 coupling constants suggest that the five-membered puckered ring-F undergoes substantial conformational changes on going from 22S to 22R isomers.     

Correlation between C and O chemical shifts and torsional strain in spiroacetals

The relationship between the ¹³C and ¹⁷O NMR chemical shifts and the dihedral energies (non-bonding interactions) of 1,4-dioxaspiro[4.4]nonane, 1,4-dioxa- and 6,10-dioxaspiro[4.5]decane, 1,4-dioxa- and 6,11-dioxaspiro[4.6]undecane, 1,5-dioxaspiro[5.5]undecane, 1,5-dioxa and 7,12-dioxaspiro[5.6]dodecane and 1,6-dioxaspiro[6.6]tridecane were analyzed. These data showed correlation of the non-bonding interactions with the chemical shift of the spiranic carbon, as well as a linear relationship between ¹³C and ¹⁷O.     

Research on furan compounds

Pressure hydrogenation using Raney nickel or ruthenium on charcoal, of secondary and tertiary -furylalkanols is described. The products are the corresponding homologs of 1, 6-dioxaspiro[4, 4]nonane and tetrahydrofuran alcohols, the relative yields being determined by the structure of the initial furan alcohol and the type of catalyst.For Part XXXII see [1].     

Synthesis of spiroacetals using functionalised titanium carbenoids

Alkylidenation of lactones with functionalised titanium carbenoid reagents (Schrock carbenes) followed by acid-induced cyclisation of the resulting enol ethers constitutes a new method for the preparation of [4.4], [4.5] and [5.5] spiroacetals (1,6-dioxaspiro[4.4]nonanes, 1,6-dioxaspiro[4.5]decanes and 1,7-dioxaspiro[5.5]undecanes, respectively, sometimes termed 5,5-, 5,6- and 6,6-spiroketals). The titanium carbenoids are easily generated from readily available thioacetals.     

Structure of bromo derivatives of 1,6-dioxaspiro[4,4]nonanes

The PMR spectra of 1,6-dioxaspiro[4.4]nonane and its monobromo and dibromo derivatives indicate that bromination of 1,6-dioxaspiro[4.4]nonanes proceeds at the 4 and 9 positions of the spiran ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1450–1451, November, 1970.     

Straightforward synthesis of 1,6-dioxaspiro[4.4]nonanes

Diols 2, easily prepared by a DTBB-catalysed lithiation of the dithioether 1 in the presence of different carbonyl compounds, react with ozone in dichloromethane at −78 °C leading, after treatment with thiourea at 20 °C, to the corresponding substituted 1,6-dioxaspiro[4.4]nonanes 3.     

Organoselenium mediated asymmetric cyclizations. Synthesis of enantiomerically pure 1,6-dioxaspiro[4.4]nonanes

The asymmetric cyclization of 1-hydroxyoct-7-en-4-one, promoted by camphorselenenyl tetrafluoroborate, generated from camphor diselenide and silver tetrafluoroborate in dichloromethane at room temperature, afforded a mixture of two diastereoisomeric E- and two diastereoisomeric Z-2-[(camphorseleno)methyl]-1,6-dioxaspiro[4.4]nonanes. These were separated by medium pressure liquid chromatography and then deselenenylated with triphenyltin hydride and AIBN to give enantiomerically pure 2-methyl-1,6-dioxaspiro[4.4]nonanes. The camphorseleno group was also substituted by an allyl function using allyltributyltin in the presence of AIBN.     

Baker's yeast reduction of prochiral γ-nitroketones. II. straightforward enantioselective synthesis of 2,7-dimethyl-1,6-dioxaspiro[4.4]nonanes

The baker's yeast reduction of 5-nitro-2,8-nonanedione 2 afforded the corresponding (2S,8S)-5-nitro-2,8-nonanediol3 with complete diastereoselectivity and high enantioselectivity. The conversion of 3 into the thermodynamic (E,E)/(Z,Z) (3:1) mixture of optically active (95% e.e.) 2,7-dimethyl-1,6-dioxaspiro[4.4]nonanes 5 was then achieved by spontaneous cyclization under the acidic conditions of the Nef reaction.     

A short and versatile route to chiral spiroketal skeletons

Different chiral spiroketal skeletons are obtained, in a versatile manner, by iterative alkylations of acetone N,N-dimethylhydrazone with iodides 2 followed by a one-pot deprotection/spirocyclization sequence. This methodology has been applied successfully to the synthesis of 1,7-dioxaspiro[5.5]undecane and 1,6-dioxaspiro[4.5]decane systems.     

An efficient synthesis of the 1,6-dioxaspiro[4.4]nonan-2-one motif of the immunosuppressive triterpenoid Phainanoid F

We describe an efficient synthesis of the 1,6-dioxaspiro[4.4]nonan-2-one motif of the immunosuppressive triterpenoid Phainanoid F and its C4 epimer. A furan oxidative spirocyclization for constructing the spiro center was used as the key step. Other important reactions involved Sharpless asymmetric dihydroxylation, Weinreb ketone synthesis and Yamaguchi esterfication. The synthesis was achieved in 11 linear steps with 17.3% overall yield.     

A stereoselective synthetic route to 1,6-Dioxaspiro[4.4]non-3-en-2-ones from cyclopropyl alkyl ketones and alpha-ketoesters

[reaction: see text] The SnCl(4)-mediated reactions of cyclopropyl alkyl ketones with alpha-ketoesters afford a novel method for the synthesis of 1,6-dioxaspiro[4.4]non-3-en-2-ones with high stereoselectivities in moderate to good yields. This process is a sequential reaction involving a nucleophilic ring-opening reaction of the cyclopropane by H(2)O, an aldol-type reaction, and a cyclic transesterification mediated by Lewis acid.     

New Heterocyclic Derivatives of α-Spirodilactones

8-Alkoxymethyl-3-bromoacetyl-3-methyl-2,7-dioxaspiro[4.4]nonane-1,6-diones react with thiourea, substituted thioureas, and 5-aryl-1,2,4-triazole-3-thiols to give new heterocyclic compounds containing an α-spirobutanolide fragment.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 913–916.Original Russian Text Copyright © 2005 by Kochikyan, Samvelyan, Arutyunyan, Avetisyan.     

Synthesis and Characterization of Two vic-Dioximes Containing the 1,3-Dioxolane Ring and 1,4-Diaminobutane and Their Cobalt(II), Nickel(II), Copper(II) and Zinc(II) Metal Complexes

Two new vic-dioxime ligands, (E,E)-N-{4-[(1,4-dioxaspiro[4.4]non-2-ylmethyl)amino]butyl}-N-hydroxy-2-(hydroxyimino)ethanimidamide (L¹H₂) and (E,E)-N-{4-[(1,4-dioxaspiro[4.5]dec-2-ylmethyl)amino]butyl}-N-hydroxy-2-(hydroxyimino)ethanimidamide (L²H₂) containing two different heteroatoms (N,O) have been prepared from anti-chloroglyoxime, N-(1,4-dioxaspiro[4.4]non-2-ylmethyl)butane-1,4-diamine (3) and N-(1,4-dioxaspiro[4.5]dec-2-ylmethyl)butane-1,4-diamine (4). Co^II, Ni^II and Cu^II complexes of the ligands have a metal:ligand ratio of 1:2 and the ligands coordinate through the two N atoms, as do most of the vic-dioximes. However, Zn^II complexes of the ligands have a metal:ligand ratio of 1:1 and the ligands are coordinated only by the N, O atoms of the vic-dioximes. In the Co^II complexes two water molecules, and in the Zn^II complexes a chloride ion and a water molecule, are also coordinated to the metal ion. The structures of the compounds were determined by a combination of elemental analysis, magnetic moments, molar conductances, thermogravimetric analysis (t.g.a.) and spectroscopic (u.v.–vis., i.r., ¹H- and ¹³C-n.m.r.) data.