Showing papers on "Cyclopropane published in 1980"

Three-membered phosphorus ring compounds

Abstract: The synthesis of novel homoand heterocyclic threemembered phosphorus ring compounds is described. Such strained ring systems are not in all cases hyperreactive substances, but may exist as isolable compounds. The structures are based on 31P NMR spectroscopic data and on single crystal X-ray structure analysis . INTRODUCTION In the past two decades, a great number of new cyclic phosphorus compounds could be synthesized. Nevertheless , monocyclic three-membered phosphorus ring systems without additional stabilization by coordination are almost unknown. This is particularly true for compounds with more than one phosphorus atom in a three—membered ring. Of all known elements, carbon shows, of course, the greatest 'ability to form cyclic compounds of ring size three. Cyclopropane was already detected nearly 100 years ago and the number .f its homoand heterocyclic derivatives is considerable. Although it is well known that a significant discontinuity in chemical properties and reactivity occurs between the first-row elements of the periodic table and those of subsequent rows, it had to be expected from the oblique relation between phosphorus and carbon that phosphorus also has a certain ability to form three—membered ring compounds with directly bonded phosphorus atoms. Besides, elemental white phosphorus consists of P4 molecules that are composed of four condensed threemembered rings. Therefore, it seemed a challenging problem to find out whether monocyclic three-menthered phosphorus ring compounds can also be sufficiently stabilized for chemical preparation and investigation. HOMOCYCLIC THREE-MEMBERED PHOSPHORUS RING COMPOUNDS The simplest phosphorus three-membered ring compound is the phosphorus hydride, cyclotriphosphane PH3 (Table 1). Already in 1965 we could detect small amounts of this compound together with other novel phosphorus hydrides in the volatile hydrolysis products of calcium phosphide by mass spectroscopy (Ref. 2). It may be seen that cyclotriphosphane is the first member of the homologous series of monocyclic phosphanes PnHn. In addition, there exist the open-chain phosphanes PnHn.2 and various series of cyclic phosphanes with lower hydrogen content and condensed ring systems. The two double underlined triphosphanes and tetraphosphanes could be separated in pure form by gas chromatography (Ref. 3). However until now, we were not able to isolate cyclo— triphosphane on a preparative scale because of its high reactivity. In contrast to the rather unstable phosphorus hydrides PnHn, their derivatives, in which the hydrogen atoms are substituted by organyl groups, are genrally much less reactive. Consequently, some of these organyl-cyclophosphanes have already been known for a long time (Ref. 4). The general procedures for their preparation are the reaction of a primary phosphine with an organyl-dichlorophosphine or the dehalogenation of a dichlorophosphine by an alkali metal and by lithiumhydride, respectively. s may be seen on Table 2, where the ring size n is given for various substituents R, mostly fiveor four-membered cyclophosphanes are formed in these reactions. for thermodynamic and kinetic reasons. In the case that R equals phenyl for instance, the five-membered ring compound Is the cyclophosphane with the highest stability. Besides, a cyclohexaphosphane of somewhat lOwer stability exists. The corresponding compounds where n equals four and lthree, however, were still unknown.

Ring Strain in Cyclopropane, Cyclopropene, Silacyclopropane, and Silacyclopropene

Abstract: The strain energy in four three-membered rings is calculated by using the appropriate isodesmic reactions. Calculations with and without d functions on the heavy atoms indicate that while these polarization functions tend to reduce ring strain, the addition of d orbitals has little effect on the predicted trends. While introduciton of unsaturation drastically increases the strain in the carbon system (cyclopropane---. cyclopropene), this is not the case for silicon (silacyclopropane--+ silacyclopropene). As a result cyclopropane and cyclopropene are predicted to be the least and most strained rings, respectively. Ring strain is a concept which is frequently used to rationalize instability and reactivity of small cyclic compounds. Recently, a novel quantitative measure of ring strain has been proposed. 1 This method makes use of isodesmic reactions in which the number of bonds of each type is formally conserved on going from reactants to products. The use of isodesmic reactions is particularly useful in quantum chemistry since the effect of correlation error is expected to be minimal in such reactions. As a result, one can use Hartree-Fock-level energy differences with some degree of confidence. In this paper the ring strain in cyclopropane, cyclopropene, silacyclopropane, and silacyclopropene is examined by using ab initio molecular orbital calculations. Cyclopropane and cyclopropene have been studied before1 and are included here for internal consistency. While semiempirical24 and ab initio5 calculations have been carried out on the silicon rings, no attempt has been made to evaluate the strain in these rings or, more importantly, their ring strain relative to the hydrocarbon analogues. In view of the apparent stability of the silicon-containing rings,6 such a comparison is clearly of interest. The methodology used in the calculations is summarized in the Methodology section, while the results of the ring strain calculations are presented and discussed in the Results and Discussion section. To aid the latter discussion approximate quadratic force fields have been generated for the four rings, and these are also presented in the Results and Discussion section.

Vibrational spectra and conformations of (chloromethyl)cyclopropane and epichlorohydrin

Abstract: The IR and Raman spectra (4000–50 cm−1) of (chloromethyl)cyclopropane and epichlorohydrin have been recorded in all three physical states. It has been concluded from the spectroscopic data and from variable temperature studies that (chloromethyl)cyclopropane exists as an equilibrium mixture of gauche (95%) and cis (5%) conformers in the liquid state, while only the gauche form persists in the solid phase. The enthalpy difference between these two rotamers was found to be 1.40±0.10 kcal mol−1. Similarly, epichlorohydrin has also been shown to exist as an equilibrium mixture of gauche-1 (70%), gauche-2 (21%) and cis (9%) conformers in the liquid state, with only the gauche-1 form remaining in the solid phase. Enthalpy differences among these conformers were determined to be 1.2±0.2 kcal mol−1 (gauche-1 vs. cis) and 0.70±0.10 kcal mol−1 (gauche-1 vs gauche-2). Apparently steric repulsions between the chlorine atom and β ring-hydrogens destabilize the cis conformation in each molecule. For each molecule, a vibrational assignment has also been proposed.

Synthesis of ring A of ambruticin and proof of its absolute stereochemistry

Abstract: Appropriately derivatized ambruticin was converted by reductive ozonolysis to tetrahydropyran 9c and cyclopropane 12a, which were synthesized from L-arabinose and (R)-Feist's acid in an unambiguous...

Substituted benzyl esters of cyclopropane carboxylic acids and their preparation, compositions containing them and methods of combating insect pests therewith, and substituted benzyl alcohols

Abstract: This invention relates to novel esters, useful as insecticides, of formula:- where R 1 and R 2 are methyl, halomethyl or halo; X is oxygen, sulphur, sulphonyl or NR 4 where R 4 is hydrogen, alkyl or carboxylic acyl; R 3 is alkyl, alkenyl or benzyl and additionally R 3 may be hydrogen when X is NR 4 ; m =0 or 1 and n = 1 to 4. The compounds may be prepared by esterification processes from the corresponding benzyl alcohols which are also new compounds.

Substituted pyridine methyl esters of tetramethyl cyclopropane carboxylic acids and their use as insecticides

Abstract: Substituted pyridine methyl esters of tetramethylcyclopropane carboxylic acids and the optical isomers thereof are prepared which correspond to the formula: ##STR1## wherein n represents an integer of 0 to 2; X independently represents alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms, alkylthio of 1 to 4 carbon atoms, alkylsulfinyl of 1 to 4 carbon atoms, alkylsulfonyl of 1 to 4 carbon atoms, trifluoromethyl, nitro, cyano, chloro, fluoro, bromo, or 3,4-methylenedioxy (when n is 2 and both X's are taken together); and R represents hydrogen, cyano or ethynyl. These compounds have been found to exhibit a high degree of insecticidal activity and compositions containing said compounds are so employed.

Nucleophilic Substitution Reactions of Cyclopropane Derivatives

Abstract: The review is devoted to the solvolysis of cyclopropane compounds. The influence of structural and external factors on the rate and direction of the reaction are considered. The bibliography includes 63 references.

Rhodium catalyzed carbonylation reactions of cyclopropanes.

Abstract: Cyclopropane was carbonylated by [Rh(CO)2Cl]2 under carbon monoxide pressure to give cyclobutanone, dipropyl ketone, propyl isopropyl ketone, and 2- or 3-methylcyclohexanone. Some other cyclopropane derivatives were also examined. Norcarane gave a small amount of bicyclo[4.2.0]octa-7-one, though phenylcyclopropane did not give any carbonylation products. The formation of polyketone was efficient in the case of methylenecyclopropane.

Carbon-13 nuclear magnetic resonance spectroscopy. Substituent-induced chemical shift effects on cyclopropyl carbons of 4-substituted cyclopropylbenzenes

Abstract: Carbon-13 chemical shifts of the cyclopropyl carbons of eleven 4-substituted cyclopropylbenzenes have been measured under conditions effectively corresponding to infinite dilution in DCCI_3. The substituent-induced chemical shifts (SCS) of both the α and β carbons of the cyclopropane ring were found to be downfield with electron-attracting groups and upfield for electron-donating groups. The trends for the β carbons correspond to those observed for the β carbons of 4-substituted phenylethenes, while the trends of the α carbons are similar to those found for the α carbons of 4-substituted isopropyl benzenes. The results for the β carbons can be rationalized by postulating a substantial contribution from a hyperconjugative resonance effect involving the σ system of the benzene ring (and its 4-substituent) and the C-α—C-β bonds of the cyclopropane ring. The effects on the α carbons are in accord with a very reasonable smaller inductive polarization of the C-α-C-β bonds than encountered for the carbons of corresponding ethenyl- or ethynylbenzenes.

Chromatostructural analysis (chromatoscopy) a new method of determination of molecular structure

Abstract: The intermolecular interaction of an isolated, adsorbed molecule with a homogeneous, flat solid surface and, thence, the thermodynamic characteristics of adsorption and adsorption chromatography at low (zero) surface coverage depend significantly on the molecular geometry of the adsorbate. Graphitized thermal carbon black (GTCB) is such a homogeneous solid and so may be used to determine some parameters of molecular structure. Use is made of the gas-chromatographically obtained Hery's constant for adsorption on GTCB with a semi-empirical molecular statistical theory of adsorption based on an atom–atom approximation for the potential function for intermolecular adsorbate–adsorbent interaction. The method is shown to be successful in determining, first, structural parameters for molecules of hexamethylbenzene, indane, 2- and 5-methylindanes, tetralin and, secondly, potential-function parameters for internal rotation in the molecules ethylbenzene and diphenyl and its methyl derivatives. By extension of the technique, experimentally obtained Henry's constants for adsorption on ion adsorbent–zeolite (NaX) have been used to determine the quadrupole moment of the cyclopropane molecule.

Reactions of Ethyl 3-Ethoxymethylene-2,4-dioxovalerate and Ethyl Ethoxymethyleneoxaloacetate with Indole Analogs

Abstract: The reactions of ethyl 3-ethoxymethylene-2, 4-dioxovalerate (1a) and ethyl ethoxy-methyleneoxaloacetate (1b) with indole analogs (2, 14, 17-19) are described. Treatment of 1a, b with 2 in ethanol followed by refluxing in acetic anhydride afforded 3, 4, 10-trisubstituted pyrimido [1, 2-a] indoles (4a, b). Hydrogenation or nucleophilic addition of 4a, b was found to occur on the pyrimidine ring in a 1, 4-fashion. Compounds 1a, b were also reacted with 14 in ethanol under ice cooling to give the 3, 4-disubstituted 9H-pyrimido-[2, 3-b] indoles (15a, b) directly. Indole (17) or 2-methylindole (18) reacted with 1a (or 1b) to give a mixture of 3-indolylmethylene derivatives (20a, b and 21a, b) and tris-(3-indolyl)-methanes (23 and 24).

Ein einfacher und allgemeiner Zugang zu 2‐Fluor‐1,3‐dienen

Abstract: Fluoroalkadienes were prepd. by Zn-catalyzed ring cleavage of 1-chloro-1-fluoro-2-halomethylcyclopropanes, obtained by treating haloalkenes with FCHCl2. Thus, ClCH2CH:CMeEt was treated with FCHCl2 to give the cyclopropane I (R = Cl) which was iodinated to give I (R = iodo). Treatment of the latter compd. with Zn gave CH2:CHCF:CMeEt. The fluorocycloheptadiene II was similarly obtained. [on SciFinder (R)]

2-(Cyclopropane-carboxamido)-2-alkenoic acids, their esters and salts, and antibacterial compositions comprising the same and a thienamycin-type compound

Abstract: ω-(2-Amino-2-carboxyethylthiol-2-(cyclopropane- carboxamido)-2-alkenoic acids, their esters and salts of the formula in the Z configuration, wherein R 2 is 2,2-dimethylcyclopropyl or 2,2-dichlorocyclopropyl; R' is hydrogen, loweralkyl of 1-6 carbon atoms, dialkylaminoalkyl with 1-6 carbon atoms in each alkyl group, or a pharmaceutically acceptable cation; R 3 is an alkylene chain of 3-7 carbon atoms, having a terminal substituent which is 2-amino-2-carboxyethylthio, or 1-(phosphono)ethylamino which selectively inhibit the metabolism of dipeptidase (E.C:3.4.13.11) and therefore are useful in combination with antibacterial products, by preference with the thienamycin class of compounds.

Process for the preparation of cyclopropane carboxylic acid esters

Abstract: 3-Halogenoethyl- or propyl-2,2-dimethylcyclopropane carboxylic acid esters, which are intermediates in the preparation of synthetic pyrethroids, are prepared by the reaction of certain halogenopentenes or hexenes with a diazoacetic ester in the presence of a catalyst which is metallic copper or a copper (II) salt, a rhodium (II) salt of a carboxylic acid or a transition metal complex of certain chiral Schiff bases. By the use of the latter class of catalysts the yield of preferred cis IR isomer may be increased relative to the other possible isomers.