- The α-secondary isotope effect in the 1,2C rearrangement of cyclopropylchlorocarbene
-
The experimental α-secondary kinetic isotope effect for the rearrangement of (2,2-dideuteriocylopropyl)chlorocarbene, 2-d2, to chlorocyclobutenes, 4 and 5, is kH/kD = 1.20 at 21° C. The corresponding value calculated by ab initio electronic structure methods is 1.12. The isotope effect very largely originates in hybridization changes at the migrating carbon atom.
- Moss, Robert A.,Liu, Weiguo,Krogh-Jespersen, Karsten
-
-
Read Online
- Collisionally Activated Mass Spectra of Ions of Polyhydroxy and Hydroxy Ether Compounds
-
Collision-induced decomposition/mass-analyzed ion kinetic energy or collisionally activated mass spectra of - ions of polyhydroxy compounds and other alcohols and ethers are reported.The - ion of each compound is produced under OH- negative ion chemical ionization mass spectrometric conditions.Characteristic fragmentations are observed that include production of -, - and - ions.Certain other fragment ions in the collisionally activated mass spectra make it possible to distinguis among structural isomers.In polyhydroxy compounds, fragmentation increases as the number of hydroxyl groups increase, and carbon-carbon bond cleavage becomes favored.
- Brumley, William C.,Andrzejewski, Denis,Sphon, James A.
-
-
Read Online
- Synthesis of deuterated mevalonolactone isotopomers
-
A synthetic route was developed for the preparation of deuterated mevalonolactones. Using low-cost deuterated reagents, this route allows for the independent introduction of deuterium labeling into any carbon position or into any combination of positions. Following this approach, the synthesis of [6,6,6-2H3]mevalonolactone, [4,4,6,6,6-2H 5]mevalonolact-one, [5,5-2H2]mevalonolactone, [5,5,6,6,6-2H5]mevalonolact-one, and [2,2,6,6,6- 2H5]mevalonolactone is described.
- Dickschat, Jeroen S.,Citron, Christian A.,Brock, Nelson L.,Riclea, Ramona,Kuhz, Henning
-
experimental part
p. 3339 - 3346
(2011/08/03)
-
- Metal-catalyzed rearrangement of homoallylic ethers to silylmethyl allylic silanes in the presence of a di-tert-butylsilylene source
-
(Chemical Equation Presented) In examining the scope of the di-rert-butylsilylene transfer to gem-disubstituted alkenes to form silacyclopropanes, we discovered an unprecedented reaction of homoallylic ethers. When silylene transfer was performed at room
- Cleary, Pamela A.,Woerpel
-
p. 5531 - 5533
(2007/10/03)
-
- Cyclobutanone-3,3-d2 and trimethylene-2,2-d2
-
An efficient five-step synthesis of cyclobutanone-3,3-d2 is reported. This ketone gives direct access through laser flash photolysis to the trimethylene-2,2-d2 diradical. The life-time of trimethylene-2,2-d2 provides an experimental showing that trimethylene and deuterium-labeled trimethylene diradicals decay to form cyclopropanes, rather than propenes.
- Baldwin, John E.,Patel, Dharmesh B.
-
-
- ANALYSE STRUCTURALE EN SERIE CYCLOBUTANIQUE. Partie 1. Derives monosubstitues et gem disubstitues du cyclobutane
-
Methylene bending mode analysis of some cyclobutane-d2 molecules reveals that in the dissolved state (solvent CCl4), bromocyclobutane occurs exclusively in a pseudo-equatorial form, whereas, under the same conditions, cyclobutanol and 1-bromocyclobutane carbonitrile exist both in pseudo-axial and pseudo-equatorial conformations.NMR spectroscopy confirms the results obtained for bromocyclobutane and leads to the conclusion that the pseudo-equatorial conformer is predominant in the case of cyclobutanol as well as in that of cyclobutane carbonitrile.A theoretical study of cyclobutanol in the gaseous state by the P.C.I.L.O. method gives results which are consistent with a pseudo-equatorial conformer.
- Karimine, Mohamed,Galsomias, Jacqueline,Lere-Porte, Jean-Pierre,Petrissans, Jean
-
p. 321 - 332
(2007/10/02)
-
- Application of 2H N.M.R. Specroscopy to Study the Incorporation of Cadaverine into Quinolizidine Alkaloids
-
The labelling patterns in (-)-lupinine (3), (-)-sparteine (4), (+)-lupanine (5), (+)-13α-hydroxylupanine (6) and (+)-angustifoline (7), derived biosynthetically from cadaverine dihydrochloride (11) in Lupinus species, have been established by 2H n.m.r. spectroscopy.The presence of 2H at both α and β positions at C-8 in the quinolizidine alkaloids (4) - (7) demonstrates that removal and replacement of hydrogen at this position is not involved in the enzymic processes leading to the tetracyclic skeleton as previously proposed.
- Robins, David J.,Sheldrake, Gary N.
-
p. 1427 - 1436
(2007/10/02)
-
- DEPROTONATION OF HYDRAZINIUM DICATIONS IN THE DIAZONIAPROPELLANE SERIES TO FORM BRIDGEHEAD IMINIUM IONS; EXTERNAL AND INTRAMOLECULAR TRAPPING
-
The reactions of hexa-alkylhydrazinium dications with bases and nucleophiles are described. 1,5-Diazonia-tricyclodecane (1) is hydrolysed rapidly by SN2 attack on the four-membered ring with ring opening (C-N+ cleavage).In all other cases deprotonation at α-C with concomitant N+-N+ cleavage (E2 reaction) is the only primary process.The cis-1,6-dimethyl-1,6-diazoniabicyclodecane ion (6), is exclusively deprotonated at a methyl group (Hofmann orientation). 1,5-Diazoniatricycloundecane (2), 1,6-diazoniatricyclododecane (3), 1,6-diazoniatricyclotridecane (4), and 1,6-diazoniatricyclotetradecane (5) ions generate bridgehead iminium ions, which may be trapped intramolecularly by the transannular amino group or externally by added nucleophiles.Reaction with cyanide ion gives detailed information on the regio- and stereo-chemistry of the trapping sequence.Although intramolecular/external trapping is truly competitive, the products of these reactions (α-amino-ammonium ions and α-aminonitriles) may be interconverted under different reaction conditions.The solvolysis of 1-(3-phenoxypropyl)-1,5-diazabicyclooctanium bromide in aqueous 48percent HBr is 103 faster than that of 3-phenoxypropyltrimethylammonium bromide, and the products are consistent with the intermediacy of the dication (2).These observations provide an explanation for the formation of 1,5-diazacyclo-octane in the reaction of 1,3-dibromopropane with hydrazine.
- Alder, Roger W.,Sessions, Richard B.,Gmuender, John O.,Grob, Cyril A.
-
p. 411 - 418
(2007/10/02)
-
- An Investigation of the Thermal Decomposition of the Methohydroxides and Methodeuterio-oxides of Some 5-N,N-Dimethylaminopent-1-enes
-
The base-catalysed thermal decomposition of a number of quaternary bases of the type (R1)2C=CH(R2)2C(R3)2CH2N+Me3X- (R1 = H, Me; R2 = H, 2H; R3 = H, 2H, Me; X = OH, O2H) has been investigated.It is shown that the reaction is initiated by attack of base (OH-, O2H-, ylide) on an allylic proton or .A mechanism for the reaction is suggested.
- Cocker, Wesley,Geraghty, Niall W. A.,McMurry, T. Brian H.,Shannon, Patrick V. R.
-
p. 2245 - 2254
(2007/10/02)
-
- ON THE MAGNITUDE OF PRIMARY ISOTOPE EFFECTS FOR PROTON ABSTRACTION FROM CARBON.
-
Primary deuterium isotope effects have been measured for the loss of an alpha proton from 4-(4-nitrophenoxy)-2-butanone. The isotope effect data showed that no significant change in transition-state structure occurred in the same region of oxyanion cataly
- Hupe,Pohl
-
p. 5634 - 5640
(2007/10/02)
-