Cyclopropanes Tris cyclopropane

Ring closure is a common feature of the reaction of sulfur tetrafluoride with cyclopropane-, cyclobutane- and cyclopentanepolycarboxylic acids. This tendency seems to be enhanced by steric crowding. Thus, m,tricarboxylic acid gives a 1 1 mixture of cyclic ether 13 and cis,trims-], 2,3-tris(trifluoromethyl)cyclopropane, whereas cyclopropane-... 

Dramatically differing effects of phase-transfer catalysts on the cyclopropanation of cw,trans,trans-cyclododecatriene (61) and a series of dienes have been reported. Addition of dichlorocarbene to (61) results in tris-cyclopropanation when cetyltri-methylammonium bromide (i) is employed, whereas with benzyl-P-hydroxyethyl-dimethylammonium ion (ii) as catalyst only monocyclopropanation (of the more strained bond) is observed (Scheme 7). From the extensive study it may be concluded that, for dichlorocarbene addition, the P-hydroxyethyl catalyst restricts potential polycyclopropanation to monocyclopropanation at the most highly substituted (or strained) double bond. With dibromocarbene a different situation results. Catalyst (i) does not effect the addition of dibromocarbene to styrene, cyclohexene, or allyl bromide while catalyst (ii), with the P-hydroxyethyl function, effects dibromocyclo-propanation, in yields of up to 80 %. 

Leucine, ethanol, tobacco, the salicylates, hypoglycin A and B, pent-4-enoic acid, ouabain, isoproterenol, mesoxalate, tris-(hydroxymethyl)-aminomethane (Tham or Tris), cyclopropane carboxylic acid, monoamine oxidase (MAO) inhibitors, a few derivatives of indole, tranylcypromine and some cyclic polycarbonyls such as rhodizonate and tetrahydroxyquinone may be included among these substances. Leucine stimulates insulin secretion in infants with leucine sensitivity as well as in normal adults, especially if infused in large amounts or if the p cells have been primed by the previous administration of a sulphonylurea. 

Trispiro[cyclopropane-l,2 2,2 3,2" -tris-l,3-benzodioxole] nomenclature, 1, 26 Tris-1,2,4-triazoles synthesis, 5, 745... 

The behavior of strained,/Zuorimiret/ methylenecyelopropanes depends upon the position and level of fluorination [34], l-(Difluoromethylene)cyclopropane is much like tetrafluoroethylene in its preference for [2+2] cycloaddition (equation 37), but Its 2,2-difluoro isomer favors [4+2] cycloadditions (equation 38). Perfluoromethylenecyclopropane is an exceptionally reactive dienophile but does not undergo [2+2] cycloadditions, possibly because of stenc reasons [34, 45] Cycloadditions involving most possible combinations of simple fluoroalkenes and alkenes or alkynes have been tried [85], but kinetic activation enthalpies (A/f j for only the dimerizations of tetrafluoroethylene (22 6-23 5 kcal/mol), chlorotri-fluoroethylene (23 6 kcal/mol), and perfluoropropene (31.6 kcal/mol) and the cycloaddition between chlorotnfluoroethylene and perfluoropropene (25.5 kcal/mol) have been determined accurately [97, 98] Some cycloadditions involving more functionalized alkenes are listed in Table 5 [99. 100, 101, 102, 103]... 

Employing protocol V with the methanesulfonamide catalyst 122, a 93 7 er can be obtained in the cyclopropanation of cinnamyl alcohol. This high selectivity translates well into a number of allylic alcohols (Table 3.12) [82]. Di- and tri-substi-tuted alkenes perform well under the conditions of protocol V. However, introduction of substituents on the 2 position leads to a considerable decrease in rate and selectivity (Table 3.12, entry 5). The major failing of this method is its inability to perform selective cyclopropanations of other hydroxyl-containing molecules, most notably homoallylic alcohols. 

In view of this behavior, the next step involved a search for an anionic sohd that was more similar to triflate. Several organic polymers with sulfonic groups were tried as supports [52]. Dowex and Deloxan were used as supports for the enf-6a-Cu(II) complex. The solid catalysts were used in the same cyclopropanation reaction (Scheme 7) and some relevant results are gathered in... 

Reaction of tris(trimethylsilyl)methyllithium 1631 with styrene oxide affords, via 1632 and 1633, the cyclopropane 1634 in 69% yield [25] (Scheme 10.11). The reactions of tris(trimethylsilyl)methyllithium 1631 have been reviewed [26]. 

The compound 251 decarbonylates on photolysis to bis(4-hydroxyaryl) acetylene 253, which is easily oxidized to the quinonoid cumulene 254. This is also obtained by thermal decarbonylation of the product of oxidation of cyclopropenone 251, the diquinocyclopropanone 252. Likewise, the blue derivative of 3-radialene 256 (a phenylogue of triketo cyclopropane) is formed from tris-(4-hydroxyaryl) cyclopropenium cation 255 by oxidation34. ... 

Attempts to prepare 1 from some other precursors were largely unsuccessful N, N , A,/-(cyclopropane-l,2,3-trimethyl)-tris(dimethylamine oxide) decomposed unspecifically above 250 °C3 and pyrolysis of l,2,3-tris(acetoxymethyl)cyclopropane gave mainly benzene3 its gas-phase pyrolysis at 570-580°C produced a mixture of at least fifteen compounds containing perhaps a small amount of l7. 

It appears that neither the lithium carbenoid pathway nor the cyclopropanation of buta-trienes are general routes to [3]radialenes. More successful is the cyclotrimerization of 1,1-dihaloalkenes via copper or nickel carbenoids, provided the substituents at the other end of the C=C double bond are not too small. Thus, tris(fluoren-9-ylidene)cyclopropane 27 was formed besides butatriene 28 from the (l-bromo-l-alkenyl)cuprate 26 generated in situ from (9-dibromomethylene)fluorene (Scheme 3)10. The cuprate complexes formed... 

A variety of functionalized [3]radialenes have been prepared starting from the appropriately substituted cyclopropanes or cyclopropenes. West and Zecher have pioneered the chemistry of [3]radialenes with quinoid substituents. The general strategy of this synthesis is outlined in Scheme 513. A tris(4-hydroxyphenyl)cyclopropenylium... 

Various other [3]radialenes bearing quinoid substituents have been synthesized analogously, for example 3814,3914,4015, 4116,4215, and the rather unstable 4317. In contrast to most other tris(quino)cyclopropanes, reduction of tris(anthraquino)cyclopropane 38 does not succeed with hydroquinone, but requires more forcing conditions (Sn/HCl or Zn/HCl). Compound 44 represents the only tropoquino-substituted [3]radialene known so far18 the black-blue crystals of this strongly electron-accepting radialene are stable to air and light. 

Hexamethyl[3]radialene (25) does not undergo Diels-Alder-reactions with the typical electron-poor dienophiles, probably because of the full substitution at the diene termini. With TCNE, however, a violet-blue charge-transfer complex is formed which disappears within 30 min at room temperature to form a 1 1 adduct (82% yield) to which structure 55 was assigned9. Similar observations were made with tris(2-adamantylidene)cyclopropane (34), but in this case cycloaddition product 56 (81% yield) was identified its allenic moiety is clearly indicated by IR and 13C NMR data12. 

The two-step reduction of tris(9-fluorenylidene)cyclopropane 2731 and of hexakis(tri-methylsilylethynyl)cyclopropane 5226a requires increasingly more negative potentials than in the cases listed in Table 1 this is, of course, a consequence of the presence of less electron-accepting substituents. Nevertheless, dianion 272 has been generated by reduction with sodium or lithium the lithium salt could be kept in THF solution for up to one year at 20 °C without detectable decomposition31. 

In the presence of nickel(0), tethered diene-VCPs react to produce eight- and five-membered ring products (Scheme 2). Palladium(O) and cobalt(m) were also tried but produced only decomposition products. However, in the presence of Wilkinson s catalyst (RhCl(PPh3)3), tethered diene-VCP 1 was cleanly converted to triene 4 in 91% yield. Although the desired cycloaddition reaction was not obtained, the cleavage of the cyclopropane ring was encouraging.22... 

Cyclopropanation of enones.1 Reaction of an enone with tris(phenylthio)-methyllithium and then with CuOTf (1 equiv.) results in a bis(phenylthio)-cyclopropane (equation I). 

Similarly, tri-O-benzyl-glucal affords the corresponding manno-configurated methoxycarbonyl cyclopropanes upon treatment with methyl diazoacetate under... 

More recently, Burgess et al. (34) used the same approach in the synthesis of a constrained phenylalanine derivative, 3-phenyl-2,3-methanophenylalanine (123). Libraries of metal complexes were screened to determine the best combination for the asymmetric cyclopropanation reaction (35). The ligands shown below were combined with AgSbFg, (CuOTf)2 PhH, RuC12(C10H14)]2, Sc(OTf)3, where tri-... 

Herrmann A, Ruettimann M, Thilgen C, Diederich F (1995) Multiple cyclopropanations of C70. Synthesis and characterization of bis-, tris-, and tetrakis-adducts and chiroptical properties of bis-adducts with chiral addends, including a recommendation for the configurational description of fullerene derivatives with a chiral addition pattern. Helv. Chim. Acta 78 1673-1704. 

Much of the recent work on the cyclopropane-propylene isomerization has had one of two objectives, either to try and determine which of the two reaction paths suggested by the early workers is involved, or to test the various theories of unimolecular reactions. Comer and Pease (1945), using catalytic hydrogenation to analyse their reaction product, but otherwise working under similar conditions to Chambers and Kistiakow-sky, suggested that all the results obtained could be represented just as well by the reaction scheme... 

Bromo- and iodocyclopropanes cannot be prepared by the direct halogenation of cyclopropanes. Substituted chloro- and bromocyclopropanes have been synthesized by the photochemical decomposition of a-halodiazomethanes in the presence of olefins iodocyclopropanes have been prepared from the reaction of an olefin, iodoform and potassium f-butoxide followed by the reduction of diiodocyclopropane formed with tri-w-butyl tin hydride. The method described employs a readily available light source and common laboratory equipment, and is relatively safe to carry out. The method is adaptable for the preparation of bromo- and chlorocyclopropanes as well by using bromodiiodomethane or chlorodiiodomethane instead of iodoform. If the olefin used will give two isomeric halocyclopropanes, the isomers are usually separable by chromatography. ... 

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