- A CONVENIENT ROUTE TO ALKYLIDENECYCLOPROPANES FROM CYCLOPROPYLDIPHENYLPHOSPHINE OXIDE AND CARBONYL COMPOUNDS
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Alkylidenecyclopropanes were readily prepared by thermal decomposition of the potassium or lithium salt of the adduct formed from the treatment of cyclopropyldiphenylphosphine oxide with n-butyl lithium and a carbonyl compound.
- Meijs, Gordon F.,Eichinger, Peter C. H.
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p. 5559 - 5560
(2007/10/02)
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- Deamination Reactions, 44. Decomposition of 1-Alkylcyclopropanediazonium Ions
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1-Methyl- (17), 1,2-dimethyl- (41, 44), 1-propyl- (64), 1-(1-methylethyl)cyclopropanediazonium ions (80), and -1-diazonium ions (93) have been generated by alkaline cleavage of the analogous nitrosocarbamates in methanol.Cyclopropyl-allyl transformation and nucleophilic displacement were the only reactions of 17, 41, 44, and 93 while elimination and 1,2-shifts of an α-hydrogen compete increasingly with 64 and 80.The stereochemistry of ring cleavage and nucleophilic displacement has been explored, using 2-D labels in the case of 17 and 93.Cyclopropanediazonium ions (1) and 41 react stereospecifically, 17 and 44 are moderately stereoselective (ca. 85:15), and 93 is entirely unselective.The data indicate a gradual changeover from concerted to stepwise mechanisms.Appreciable stabilization of the positive charge is required to reach the SN1 extreme.
- Kirmse, Wolfgang,Rode, Jutta,Rode, Klaus
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p. 3672 - 3693
(2007/10/02)
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- Intramolecular Steric Factors in the Thermolysis of 4-Alkylidine-1-pyrazolines
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Secondary deuterium kinetic isotope effects and product proportions are measured for several methyl-substituted 4-methylene-1-pyrazolines and deuterated isotopomers.The kinetic data support a single-bond-cleavage mechanism, and the products indicate that three modes of ring closure are required.Evidence is presented for a series of monomethyl compounds to suggest that the mechanism is more complex than a two-step scheme would predict and that the interconversion of a series of intermediates 46 is required.
- LeFevre, Gerard N.,Crawford, Robert J.
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p. 1019 - 1027
(2007/10/02)
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- PROTON MOBILITY OF HYDROGEN IN SUBSTITUTED METHYLENECYCLOPROPANES AND VINYLCYCLOPROPANES
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The kinetic acidities of methylenecyclopropane, 1,1-dicyclopropylmethylenecyclopropane, and 1-methyl-1-cyclopropylmethylenecyclopropane in the KCH2SOCH3-(CH3)2SO system were determined; the rate constants for the isomerization of the last hydrocarbon into 1,1-dicyclopropylethylene and of 1,1,dimethylmethylenecyclopropane into 1-methyl-1-cyclopropylethylene were also determined.The introduction of the vinyl group into the trimethylene ring and also the introduction of an exocyclic double bond lead to a marked increase in the proton mobility of the hydrogen.Electron-donating methyl and cyclopropyl groups at the double bond of methylenecyclopropane reduce its kinetic acidity.
- Akhachinskaya, T. V.,Shapiro, I. O.,Donskaya, N. A.,Shabarov, Yu. S.,Shatenshtein, A. I.
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p. 421 - 426
(2007/10/02)
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- THE EFFECT OF THE DIETHYLPHOSPHONATE GROUP ON FREE RADICAL STABILITIES
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The diethylphosphonate substituent is free radical stabilizing by a conjugation mechanism as judged by its effect on the rate of the methylenecyclopropane rearrangement.
- Creary, Xavier,Benage, Brigitte,Mehrsheikh-Mohammadi, M. E.,Bays, J. Philip
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p. 2383 - 2386
(2007/10/02)
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