Synthesis of thiadiazoles and 1,2,4-triazoles derived from cyclopropane dicarboxylic acid

New heterocyclic derivatives of cyclopropane dicarboxylic acid comprising thiadiazole and 1,2,4-triazole moieties are reported. Reaction of 1,1-cyclopropane dicarboxylic acid (1) with thiosemicarbazide and phosphorous oxychloride resulted in 1,1-bis (2-amino-1,3,4-thiadiazol-5- yl)cyclopropane (2). Cyclopropane dicarboxylic acid thiosemicarbazide (6) was converted into 1,1-bis(3-thio-4H-1,2,4-triazol-5-yl) cyclo- propane (7) by ring closure in an alkaline medium. The thiadiazole 2 and the triazole 7 were converted into a variety of derivatives.     

Synthesis and some transformations of bicyclic γ-lactones with a fused cyclopropane ring

Reductive cyclization of 4-hydroxymethyl-5,5-dimethyl(or pentamethylene)-2,5-dihydrofuran-2-ones by the action of sodium tetrahydridoborate gave bicyclic compounds in which the lactone ring is fused to a cyclopropane ring. Hydrolysis of the products with aqueous sodium hydroxide resulted in the formation of the corresponding disodium cyclopropane-1,1-dicarboxylates, which reacted with alkyl halides to produce the diesters. Acid hydrolysis of the fused systems was accompanied by opening of the cyclopropane ring with formation of 4-chloromethyl-5,5-dimethyl-2-oxotetrahydrofuran-3-carboxylic acid.     

Polymerization of substituted cyclopropanes. III. Anionic polymerizations of 2-substituted cyclopropane-1,1-dicarbonitriles

To investigate further the anionic ring-opening polymerization of substituted cyclopropane 2-phenylcyclopropane-1,1-dicarbonitrile (I), 2-ethylcyclopropane-1,1-dicarbonitrile (II), and 2,2-dimethylcyclopropane-1,1-dicarbonitrile (III) were prepared and polymerized with sodium cyanide in N,N-dimethylformamide. Under these conditions only I polymerized well. The polymer in I was soluble in hot sulfolane and the inherent viscosity was 0.5 dl/g (conc. 0.5 g in 100 ml). This result supports the previously postulated mechanism that a cyclopropane ring with properly positioned electron-donating and electron-withdrawing substituents can polymerize by opening the bond activated by a “push–pull” system.     

Rearrangements and cyclizations—XVI: Ring-opening reactions of 1,1-diacetylcyclopropane with hydrazine and hydroxylamine derivatives as the novel synthesis of β-X-ethyl substituted pyrazoles and isoxazoles

The reactions of 1,1-diacetylcyclopropane (1) with a number of hydrazine and hydroxylamine derivatives proceed via cyclopropane ring opening with incorporation of external nucleophile (solvent) to give the 4-β-X-ethyl derivatives of 3,5-dimethylpyrazoles and -isoxazoles, a novel route to these heterocycles. This ring cleavage occurs especially smoothly in water as a solvent. A rationale for this unusually mild nucleophilic cyclopropane ring opening is discussed.     

Sc(OTf)3-catalyzed smooth tandem [3+2] cycloaddition/ring opening of donor-acceptor cyclopropane 1,1-diesters with enol silyl ethers

Catalyzed by Lewis acids, donor-acceptor cyclopropane 1,1-diesters reacted with enol silyl ethers to afford 1,6-dicarbonyl compounds in moderate to excellent yields. This supplied a mild carbon-carbon bond-forming method from the ring opening of cyclopropanes. A smooth tandem [3+2] cycloaddition/ring opening process has been clearly proved by an independent experiment.     

[3+2] Cyclodimerization of 2-arylcyclopropane-1,1-diesters. Lewis acid induced reversion of cyclopropane umpolung

A novel Lewis acid catalyzed [3+2] cyclodimerization of 2-arylcyclopropane-1,1-dicarboxylates is reported. It is the first example of a reaction wherein a donor-acceptor cyclopropane provides two carbons in a newly formed ring. The described cyclodimerization represents a general convenient approach to polyfunctionalized cyclopentanes.     

Titanocene(II)-promoted carbonyl cyclopropylidenation utilizing 1,1-dichlorocyclopropanes

A variety of alkylidenecyclopropanes bearing various substituents on their cyclopropane ring were obtained by the titanocene(II)-promoted reaction of 1,1-dichlorocyclopropane derivatives with carbonyl compounds including esters and lactones.     

Synthesis and radical ring opening behaviour of 1,1-difluoro-2-heptyl-2-vinylcyclopropane and some of its isomers

The syntheses and characterisations of 1,1-difluoro-2-heptyl-2-vinylcyclopropane and some of its isomers are described together with attempts to effect free radical ring opening polymerisation. We have recently shown that the parent monomer, 1,1-difluoro-2-vinylcyclopropane, undergoes predominantly 1,4-addition ring opening in contrast to the more usual 1,5-ring opening of other substituted vinylcyclopropanes and we find that the same anomalous behaviour occurs in this work confirming the influence of fluorine on the course of cyclopropane ring opening proposed by Dolbier. The presence of an alkyl chain modifies the ratios of 1,4- to 1,5-ring opening compared to that found in the unsubstituted parent monomer. In addition an the unexpected behaviour of different alkyl substituted buta-1,3-dienes towards difluorocarbene addition is described.     

1,1-二甲基-2-芳基环丙烷的光化学

报道了用二环己烷胺锂盐作为碱,由苄氯和异丁烯合成1,1-二甲基-2-(1-萘基)环丙烷(1)和1,1-二甲基-2-(9-菲基)环丙烷(2)的方法,(1)或(2)的直接光解得到2-甲基-4-芳基-1-丁烯(主要产物),芳基乙烯和2,3-二甲基-2-丁烯。二苯甲醇和二苯甲酮存在下的敏化试验表明,(1)和(2)都淬灭苯频哪醇化反应,并证明确实发生了三线态向(1)或(2)的能量转移,因此是单线态的反应,不存在由芳基所造成的垂直激发态的稳定化现象,这就揭示了芳环的P轨道不参与反应过渡态。因此,重排反应系经过Hückel式四电子周环过渡态进行,该过渡态遵循“大K值对小K值“规则。     

Nitrosation of adamantyl dichlorocyclopropanes as a new approach to adamantyl isoxazoles

Nitrosation of 2-(1-adamantylmethyl)-1,1-dichlorocyclopropane with either adduct NOCl?(SO₃) _n or nitrosonium tetrafluoroborate gives 3- and 4-(1-adamantylmethyl)-5-chloroisoxazoles in good yields. The presence of a linker between cyclopropane ring and adamantane moiety is essential for enabling nitrosation—heterocyclization of adamantyl 1,1-dichlorocyclopropanes.

     

Polymerization of vinylcyclopropanes. II

1,5-Type polymerization of vinylcyclopropane proceeding by the opening of both the double bond and the cyclopropane ring was found. Some other vinylcyclopropane derivatives, 1,1-dichloro-2-vinylcyclopropane, 1,1-dibromo-2-vinylcyclopropane, isopropenylcyclopropane, 1-methyl-1-vinylcyclopropane, 1,1-dichloro-2-methyl-2-vinylcyclopropane, and cis- and trans-1-chloro-2-vinylcyclopropane, were investigated. The observation of infrared spectra, NMR spectra, and other data indicated that the radical polymerization of these compounds gave principally 1,5-type polymer, while in cationic polymerization 1,2-type was predominant. The behavior of the polymerization was discussed in terms of the stability of a cyclopropylcarbinyl ion or radical which is formed in the initiation and propagation steps.     

The effect of fluorine substituents on the structure of cyclopropane. The structure of 4,4,8,8-tetraf1uorotricyclo-(5.1.0.0.3,5) octane

The first x-ray structure determination of a fluorine-substituted cyclopropane is reported. The title compound was synthesized via $\text{bis}$ difluorocarbene addition to 1,4-cyc1ohexadiene and its structure determined via x-ray crystallographic techniques. Its cyclopropane bondlengths (1.552 and 1.452) are very similar to those reported earlier in a microwave study of the parent 1,1-difluorocyclopropane, while its cyclohexane ring is virtually planar.     

Reactions of donor-substituted furans with electrophilic ethylenes

2-Methoxyfuran and 2-p-tolyloxyfuran were attacked at the 5-position by tetracyanoethylene or the super-electrophilic 2,2-bis(trifluoromethyl)ethylene-1,1-dicarbonitrile affording (Z)-3-cyclopropylacrylic esters, substituted in the 3-membered ring. Initially formed zwitterions undergo simultaneous opening of the furan and closure of the cyclopropane ring. In the presence of pyridine, 1,3-prototropy converts the zwitterion to 5-substitution products of the furans.     

Stereospecific palladium(0)-catalyzed reduction of 2-cyclobutylidenepropyl esters. A versatile preparation of diastereomeric monoterpenoids: (±)-fragranol and (±)-grandisol

Mixtures of (E and Z)-2-cyclobutylidenepropyl sulfonates, readily available from α,α-disubstituted cyclobutanones arising from suitable cyclopropane derivatives ring expansion, underwent regioselective and stereospecific reduction by formate anion to offer, through π-1,1-trimethyleneallylpalladium complexes formed upon treatment with palladium(0), a new and convenient entry to the diastereomeric four-membered ring monoterpenoids (±)-fragranol and (±)-grandisol.     

Polymerizations of substituted cyclopropanes. II. Anionic polymerization of 1,1-disubstituted 2-vinylcyclopropanes

Among the four 1,1-disubstituted 2-vinylcyclopropanes, diethyl 2-vinylcyclopropane-1,1-dicarboxylate (Ia), 2-vinylcyclopropane-1,1-dicarbonitrile (Ib), ethyl 1-cyano-2-vinylcyclopropanecarboxylate (Ic), and 1,1-diphenyl-2-vinylcyclopropane (Id), Ib and Ic polymerized well with sodium cyanide in N,N-dimethylformamide. Ib was most reactive and a polymer (IIb) from Ib exhibited an inherent viscosity of 1.05 dl/g (concentration of 1.0 g in 100 ml of 95% H₂SO₄). All experimental results indicated that the polymerization proceeded by ring opening and that the structure of the polymers had pendant vinyl groups. The polymer IIc from Ic was soluble in common solvents like acetone, but IIb was soluble only in 95% H₂SO₄. Reactions of those compounds with benzenethiolate ion in ethanol yielded addition products that supported the ring-opening polymerization of those monomers. In the postulated mechanism of polymerization cyanide ion attacks the carbon of a cyclopropane ring with electron-releasing vinyl group and the resulting anion is thereby stabilized by two electron-withdrawing substituents. The propagation takes place by the reaction of the anion with another monomer molecule.     

On the electronic and molecular structures of methyl chloride,cyclopropyl chloride and 1,1-dichlorocyclopropane

Ab initio SCF—MO calculations have been carried out on cyclopropyl chloride and 1,1-dichlorocyclopropane, to illuminate the effect of the substituent upon the cyclopropane ring. For cyclopropyl chloride, reasonable agreement is found with experimental findings. For 1,1-dichlorocyclopropane, excellent agreement is found with the results from a recent NMR study. As a means of studying the effect of a change in basis set, calculations are also carried out on methyl chloride.     

Tricyclo[2.1.0.01,3]pentane

The reaction of 1,1-dibromo-2,3-bis(chloromethyl)cyclopropane with methyllithium leads initially to ring closure to 1-bromo-2-chloromethylbicyclo[1.1.0]butane. Further reaction leads to an unstable compound which reacts with phenylthiol to give 2-vinyl-1-cyclopropyl phenyl sulfide and undergoes thermal rearrangement at ∼ -50°C to give cyclopentadiene. Strong evidence is presented which suggests that tricyclo[2.1.0.01,3]pentane may be the intermediate.     

Transformations of <Emphasis Type="Italic">gem</Emphasis>-dibromoarylcyclopropanes under nitrosation conditions on treatment with NOCl·(SO<Subscript>3</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

The reaction of 2-aryl-1,1-dibromocyclopropanes with adduct NOCl·(SO₃) _n leading to 3-aryl-5-bromoisoxazoles as a result of nitrosation—heterocyclization of the cyclopropane ring was studied. The reaction is accompanied with electrophilic aromatic bromination. The mechanism of the transformation was discussed, the optimal reaction conditions to enhance the reaction selectivity were developed.     

Synthesis and radical ring-opening polymerization behavior of vinylcyclopropane bearing six-membered cyclic acetal moiety

Synthesis and radical ring-opening polymerization of vinylcyclopropane bearing six-membered cyclic acetal moiety, 1-vinyl-4,8-dioxaspiro[2.5]octane (1), were carried out. 1 was prepared by the reaction of 1,1-dichloro-2-vinylcyclopropane and 1,3-propanediol in DMF in the presence of a base. Radical polymerization of 1 was carried out in the presence of an appropriate initiator (3 mol % vs. 1) at 60 and 120°C in degassed sealed ampoules for 20 h. A colorless transparent viscous polymer was obtained by the isolation with preparative HPLC. The structure of poly(1) was determined to consist of two 1,5-ring-opened units and a unit bearing no olefinic moiety. The difference of the activation energies for the ring-opening reaction of the cyclopropane ring calculated by the molecular orbital method could explain the selectivity in the direction of the cleavage of the cyclopropane ring. Acid hydrolysis of poly(1) afforded the corresponding polyketone in quantitative conversion. © 1996 John Wiley & Sons, Inc.     

Cascade dimerization of 2-styryl-1,1-cyclopropanedicarboxylate upon treatment with gallium trichloride

2-Styrylcyclopropane-1,1-dicarboxylate treated with anhydrous gallium trichloride undergoes dimerization with the cyclopropane ring opening and the styryl substituent double bond involvement, leading to the formation of polysubstituted cyclic and bicyclic structures with the predominance of the former or the latter depending on the reaction conditions. Most compounds are formed with very high diastereoselectivity. Thirteen major and minor dimeric structures were isolated and reliably characterized, two of which were found to additionally include a chlorine atom. A rare for the reactions of donor-acceptor cyclopropanes example of the formation of a product with the fused cyclobutane ring was effected at–80 °C. Plausible mechanisms of observed processes were discussed.