Electrophilic additions to allenes. IV. Concerning the nature of the ortho-nitro group effect in the reaction of arenesulphenyl chlorides with allenes

1980 ◽  
Vol 58 (12) ◽  
pp. 1275-1279 ◽  
Author(s):  
Dennis G. Garratt ◽  
Pierre L. Beaulieu
Keyword(s):  
Transition State ◽  
Nitro Group ◽  
Methylene Chloride ◽  
Group Effect ◽  
Steric Interactions ◽  
Electrophilic Additions ◽  
Type Intermediate

The reactions of twelve arenesulphenyl chlorides, five of which contained an ortho-nitro substituent, with ten 1,3-disubstituted allenes, using methylene chloride as solvent, are described. No evidence for a special ortho-nitro group effect involving a spirosulphurane type intermediate is observed. Variations in the chemoselectivity and configurational-selectivity of the additions are interpreted in terms of steric interactions in the product determining transition state.

Reaction mechanism studies. 5. The mechanism of the diaxial → diequatorial rearrangement of β-chlorothioethers

1968 ◽  
Vol 46 (1) ◽  
pp. 9-13 ◽  
Author(s):  
J. F. King ◽  
K. Abikar
Keyword(s):  
Reaction Mechanism ◽  
Transition State ◽  
Nitro Group ◽  
Ion Pair ◽  
Concerted Mechanism

p-Methoxy- and p-nitro substituted analogues (1b and 1c) of the diaxial β-chlorothioether 2β-chloro-3α-(phenylthio)-5α-cholestane (1a), have been prepared and found to undergo the diaxial → diequatorial rearrangement. The rates of rearrangement of these compounds show the sequence p-methoxy > H > p-nitro. It is concluded that the transition state for the rearrangement is polarized in the sense of a sulfonium chloride (3). The rearrangement of 1a is 1600 times faster in butanol than in decalin (at 110°). There is thus no inherent insensitivity to solvent change in a rearrangement in which there may be a "four-atom arrangement" in the transition state, a conclusion relevant to previous work on the diaxial → diequatorial rearrangement of 1,2-dibromides (1). It was further found that the nitro group slowed the rearrangement (at 110°) more in butanol than in decalin, an observation regarded as consistent with, but not requiring, the incursion of a merged ion-pair, cyclic concerted mechanism.

REACTIONS OF SUGAR CHLOROSULFATES: VII. SOME CONFORMATIONAL ASPECTS

1966 ◽  
Vol 44 (13) ◽  
pp. 1483-1491 ◽  
Author(s):  
A. G. Cottrell ◽  
E. Buncel ◽  
J. K. N. Jones
Keyword(s):  
Transition State ◽  
Sulfuryl Chloride ◽  
Reaction Conditions ◽  
Steric Interactions

The reaction of sulfuryl chloride with several 1,6-anhydro-hexosans has yielded crystalline, fully chlorosulfated derivatives. Replacement of the chlorosulfate moieties by chlorodeoxy groups could not be achieved under the reaction conditions employed. This non-reactivity is discussed in terms of steric interactions in the transition state for substitution.An examination of some chloro-substituted sugar chlorosulfates confirmed that an axial chlorodeoxy group in a glycopyranoside deactivates a neighboring equatorial chlorosulfate group and thus prevents further chlorodeoxy groups being introduced into such positions. Methyl α-D-altropyranoside, methyl α-L-rhamnopyranoside, methyl α-D-lyxopyranoside, L-rhamnose, and D-lyxose were reacted with sulfuryl chloride. The resulting products were those expected if these sugars reacted primarily in the C1 conformation.

Electrophilic cleavage of cyclopropanes. II. Concerning the effect of increasing electron demand upon the product-determining transition state in the reaction of 4-substituted-2-nitrobenzenesulphenyl chlorides and benzenesulphenyl chlorides with tetracyclo[3.2.0.02,7.04,6]heptane (quadricyclene)

1980 ◽  
Vol 58 (10) ◽  
pp. 1014-1020 ◽  
Author(s):  
Pierre L. Beaulieu ◽  
Ann Kabo ◽  
Dennis G. Garratt
Keyword(s):  
Transition State ◽  
Nitro Group ◽  
Phenyl Ring ◽  
Relative Proportion ◽  
Electron Demand

The effect of increasing electron demand upon the product-determining transition state in the reaction of arenesulphenyl chlorides with tetracyclo[3.2.0.02,7.04,6]heptane has been investigated. As the electron donating ability of the remote substituents on the phenyl ring of the sulphenyl chloride is varied from nitro to methoxy the relative proportion of adducts derived from edge-on attack is found to increase relative to that of adducts derived from corner attack. An ortho-nitro group was found to lead to a stabilizing interaction only in the case of 2,4-dinitrobenzenesulphenyl chloride. A mechanism involving the competition between the two conceptual modes of approach is suggested.

Cyano and nitro group effect on the rate of methoxydenitration reaction in the pyrrole and benzene ring

1984 ◽  
Vol 49 (13) ◽  
pp. 2375-2377 ◽  
Author(s):  
Francesca Bazzano ◽  
Paolo Mencarelli ◽  
Franco Stegel
Keyword(s):  
Nitro Group ◽  
Benzene Ring ◽  
Group Effect

The Sn mechanism in aromatic compounds. XXXVIII. Comparative reactivity of 1-Halogeno-2,6-dinitrobenzenes and some other halogenonitrobenzenes

1969 ◽  
Vol 22 (12) ◽  
pp. 2555 ◽  
Author(s):  
MEC Biffin ◽  
J Miller ◽  
R Roper
Keyword(s):  
Nitro Group ◽  
Aromatic Compounds ◽  
Steric Effects ◽  
Reference Standard ◽  
Group Mobility ◽  
Steric Interactions ◽  
Leaving Group ◽  
Typical Range ◽  
Comparative Reactivity

The reactivity of 1-halogeno-2,6-dinitrobenzenes with methanolic methoxide has been studied quantitatively and compared with the results of similar studies of o- and p-halogenonitrobenzenes and 1-halogeno- 2,4-dinitrobenzenes. Adverse steric interactions of the ortho-nitro group are very small in the o-halogenonitro- and 1-halogeno-2,4- dinitrobenzenes. The interactions are substantially larger in the reactions of 1-halogeno-2,6-dinitrobenzenes in displacement of Cl, Br, and I, but not of F, but they are small compared to steric interactions found in many other classes of reactions. ��� Steric effects are observed as a reduction in rates affecting values of the Substituent Rate Factors of the o-nitro group, and affecting also the mobility as a leaving group of Cl, Br, and I, but not of F. However, since Cl is the usual reference standard for leaving group mobility, that of F appears as having an unusually high value. Nevertheless a depression of the mobility of iodine from its typical range is also evident.

π-Facial stereoselectivity in the Diels–Alder reactions of a rigid carbocyclic diene: spiro(bicyclo[2.2.1]heptane-2,1′-[2,4]cyclopentadiene)

1991 ◽  
Vol 69 (1) ◽  
pp. 179-184 ◽  
Author(s):  
D. Jean Burnell ◽  
Zdenek Valenta
Keyword(s):  
Transition State ◽  
Key Words ◽  
Diels Alder ◽  
Steric Interactions

The plane-nonsymmetrical diene spiro(bicyclo[2.2.1]heptane-2,1′-[2,4]cyclopentadiene) (2) was synthesized, and the π-facial stereoselectivity of its Diels–Alder cycloadditions with three cyclic dienophiles was examined. Adduct ratios were very similar, and the selectivity is surmised to be mainly the result of steric interactions at the transition state. Key words: facial stereoselectivity, Diels–Alder, cycloaddition.

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