3968-89-6Relevant academic research and scientific papers
Polylithiumorganic compounds. Part 29: C,C Bond cleavage of phenyl substituted and strained carbocycles using lithium metal
Maercker, Adalbert,Oeffner, Kristian S.,Girreser, Ulrich
, p. 8245 - 8256 (2007/10/03)
The reaction of phenyl substituted cyclopropanes phenylcyclopropane and 1,1-diphenylcyclopropane, phenyl substituted bicyclobutanes 1- phenylbicyclobutane, 1-methyl-3-phenylbicyclobutane, 1-methyl-2,2- diphenylbicyclobutane, as well as phenyl substituted spiropentanes phenylspiropentane and 1,1-diphenylspiropentane with lithium metal or lithium di-t-butylbiphenyl (LiDBB) was investigated. Under suitable reaction conditions and choice of solvent in all cases cleavage of the single bond next to the activating phenyl group was observed. The dilithiumorganic compounds thus obtained are sufficiently stable and can be trapped with electrophiles. Lithium hydride elimination is observed as follow-up reaction only in a few cases. The corresponding anions of the strained ring systems 1-lithio-2,2- diphenylcyclopropane, 1-lithio-3-phenylbicyclobutane, 1-lithio-3-methyl-2,2- diphenylbicyclobutane, and 1-lithio-4-phenylspiropentane, which can be obtained by lithium bromine exchange or by metalation of the unsubstituted carbocycle, do not show any cleavage upon reaction with lithium metal. The reaction of phenyl substituted cyclopropanes, bicyclobutanes as well as spiropentanes with lithium metal with formation of highly reactive dilithiumorganic compounds was investigated. In all cases cleavage of the bond next to the phenyl substituent(s) was observed.
Synthesis and transformations of metallacycles 26. Cp2ZrCl2-catalyzed cycloalumination of substituted allenes with Et3Al
Khafizova,Ibragimov,Gil'fanova,Khalilov,Dzhemilev
, p. 2188 - 2192 (2007/10/03)
Catalytic cycloalumination of 1-alkyl(phenyl)alleres with triethylaluminum (5 mol.% of Cp2ZrCl2 as the catalyst, -20 °C, 4 h, hexane) afforded methylene- and alkyl(benzyl)idene-substituted alumacyclopentanes.
A short synthesis of γ-lactams via the spontaneous ring expansion of β-lactams
Black,Olson,Abt
, p. 2729 - 2733 (2007/10/02)
β-Lactams, derived via the cycloaddition of chlorosulfonyl isocyanate to alkenes, undergo thermal rearrangement at room temperature to affort γ-lactams.
Radical ions in photochemistry. 21. The photosensitized (electron transfer) tautomerization of alkenes; the phenyl alkene system
Arnold, Donald R.,Mines, Shelley A.
, p. 689 - 698 (2007/10/02)
Alkenes, conjugated with a phenyl group, can be converted to nonconjugated tautomers by sensitized (electron transfer) irradiation.For example, irradiation of an acetonitrile solution of the conjugated alkene 1-phenylpropene, the electron accepting photosensitizer 1,4-dicyanobenzene, the cosensitizer biphenyl, and the base 2,4,6-trimethylpiridine gave the nonconjugated tautomer 3-phenylpropene in good yield.Similarly, 2-methyl-1-phenylpropene gave 2-methyl-3-phenylpropene, and 1-phenyl-1-butene gave E- and Z-1-phenyl-2-butene.The reaction also works well with cyclic alkenes.For example, 1-phenylcyclohexene gave 3-phenylcyclohexene, and 1-(phenylmethylene)cyclohexane gave 1-(phenylmethyl)cyclohexene.The proposed mechanism involves the initial formation of the alkene radical cation and the sensitizer radical anion, induced by irradiation of the sensitizer and mediated by the cosensitizer.Deprotonation of the radical cation assisted by the base gives the ambident radical, which is then reduced to the anion by the sensitizer radical anion.Protonation of the ambident anion at the benzylic position completes the sequence.Reprotonation at the original position is an energy wasting step.Tautomerization is driven toward the isomer with the higher oxidation potential, which is, in the cases studied, the less thermodinamically stable isomer.The tautomerization of 2-methyl-1-phenylbutene gave both 2-phenylmethyl-1-butene and 2-methyl-1-phenyl-2-butene (E and Z isomers), while 2,3-dimethyl-1-phenylbutene gave only 3-methyl-2-phenylmethyl-1-butene.In the latter case, steric interaction of the methyls on the isopropyl group prevents effective overlap of the tertiary carbon-hydrogen bond with the singly occupied molecular orbital, thus inhibiting deprotonation from this site.Key words: photosensitized, electron transfer, alkene, tautomerization, radical cation.
1-(Phenylsulfonyl)-2-(trimethylsilyl)ethane: A Valuable Intermediate for Synthesis of Olefins, Allyltrimethylsilanes, β-Trimethylsilyl Ketones, Vinyl Sulfones, 2-(Phenylsulfonyl)allyl Alcohols, and Varied Trimethylsilyl Derivatives
Hsiao, C.-N.,Shechter, H.
, p. 2688 - 2699 (2007/10/02)
1-(Phenylsulfonyl)-2-(trimethylsilyl)ethane (1), prepared from 1-(trimethylsilyl)-2-(thiophenoxy)ethane and hydrogen peroxide, is converted by n-butyllithium to 1-(phenylsulfonyl)-1-lithio-2-(trimethylsilyl)ethane (2).Primary halides effect alkylation of 2 to 2-(phenylsulfonyl)-1-(trimethylsilyl)alkanes (3), reactions of which with n-butyllithium and then primary halides give higher 2-(phenylsulfonyl)-1-(trimethylsilyl)alkanes (5).Debenzenesulfonyltrimethylsilylation of 3 and 5 occurs efficiently with tetra-n-butylammonium fluoride (6) to yield mono- and disubstituted terminal olefins (7 and 8, respectively). 2-(Phenylsulfonyl)-3-(trimethylsilyl)-1-alkanols (14) result from reactions of 2 with aldehydes and ketones and then acidification.Allyltrimethylsilanes (18) are obtained by reductive elimination of mesylates (17) of 14 with sodium amalgam in methanolic disodium hydrogen phosphate. 2-(Phenylsulfonyl)-3-(trimethylsilyl)-1-propene (23), a 1-cationic-2-anionic equivalent (33), is preparable by (1) condensation of 1 and formaldehyde to 2-(phenylsulfonyl)-3-(trimethylsilyl)-1-propanol (24), (2) conversion of 24 by triphenylphosphine/carbon tetrachloride to 1-chloro-2-(phenylsulfonyl)-3-(trimethylsilyl)propane (25), and (3) elimination of 25 with triethylamine. β-Trimethylsilyl ketones (35) are produced by sodium amalgam reduction of α-phenylsulfonyl β-trimethylsilyl ketones (34) obtained by oxidation of 2-(phenylsulfonyl)-3-(trimethylsilyl)-1-propanols (14, R2 = H) with chromic acid sulfonic acid in acetone.Acidification of the adducts from 2 and epoxides yields 3-(phenylsulfonyl)-4-(trimethylsilyl)-1-butanols (38).Primary and secondary alcohols 38 are converted by chromic acid/sulfuric acid to 3-phenyl sulfonyl 4-trimethylsilyl aldehydes and ketones (39). n-Butyllithium effects cyclization of methanesulfonates (40) of 37 to 1-(phenylsulfonyl)-1-cyclopropanes (42) with displacement of lithium methanesulfonate. 1-(Phenylsulfonyl)-2-n-hexyl-1-cyclopropane (46a) and 1-(phenylsulfonyl)-2-phenyl-1-cyclopropane (46b) are eliminated by 6 to 1-n-hexyl-2-methylenecyclopropane (47a) and 1-methylene-2-phenylcyclopropane (47b), respectively. 2-(Phenylsulfonyl)-1-alkenes (49) are prepared by reactions of 6 with 2-(phenylsulfonyl)-2-chloro-1-(trimethylsilyl)alkanes (48) obtained (1) from tert-butyl hypochlorite and 2-(phenylsulfonyl)-2-lithio-1-(trimethylsilyl)alkanes(4) and/or (2) by reaction of 1-(phenylsulfonyl)-1-chloro-2-(trimethylsilyl)ethane (50) with n-butyllithium and alkylations of the resulting 1-(phenylsulfonyl)-1-chloro-1-lithio-2-(trimethylsilyl)ethane (51).Synthesis of 50 is best effected by base-catalyzed cleavage of 3-(phenylsulfonyl)-3-chloro-4-(trimethylsilyl)-2-butanone (54) prepared from 1-acetyl-1-phenylsulfonyl)-2-(trimethylsilyl)ethane (53) and ...
