56701-47-4

Upstream product

• 100-42-5 styrene 
• 24519-03-7 5,5-dimethyl-N-nitroso-2-oxazolidone 
• 66680-86-2 isobutenyltributyltin 
• 1666-17-7 benzaldehyde p-toluenesulfonylhydrazone 
• 100-52-7 benzaldehyde 
• 72436-45-4 (4-formylphenyl)phosphonic acid diethyl ester 
• 99405-03-5 1-iodo-4-(1,1-dimethoxymethyl)benzene 
• 99405-05-7 4-(diethoxyphosphoryl)benzaldehyde dimethyl acetal 
• 598-25-4 Dimethylallene 
• 99405-07-9 C₁₈H₂₃N₂O₅PS 
• 65108-25-0 2-Phenyl-3,3-dimethylmethylenecyclopropane 
• 908094-04-2 phenyldiazomethane 
• 100-44-7 benzyl chloride 
• 58926-06-0 1-chloro-2-methyl-1-(trimethylsilyl)-1-propene 

Downstream Products

• 65354-76-9 (2,2-dimethyl-cyclopropylidenemethyl)-benzene 
• 65354-77-0 (2,2-dimethyl-cyclopropylidenemethyl)-benzene 

Relevant academic research and scientific papers

THE PYRIDINE N-OXIDE GROUP. A POTENT RADICAL STABILIZING FUNCTION

The rate of the methylenecyclopropane rearrangement is greatly enhanced by the 4-pyridyl N-oxide group due to spin delocalization in the transition state which imparts nitroxide radical character to the biradical intermediate.

Cobalt- and Silver-Promoted Methylenecyclopropane Rearrangements

The rate of the methylenecyclopropane rearrangement is enhanced by an alkyne-Co2(CO)6 complex bonded to the para position of a benzene ring. This is explained by a stabilizing effect on the transition state leading to the biradical intermediate. Computational studies indicate that the benzylic-type biradical intermediate is stabilized by a delocalization mechanism, where spin is delocalized onto the two cobalt atoms. Silver cation also enhances the rate of the methylenecyclopropane rearrangement. Computational studies suggest that silver cation can also stabilize a benzylic radical by spin delocalization involving silver. In the case of the silver-promoted reactions, the rate enhancements in a series of aryl-substituted methylenecyclopropanes correlate with σ+ values. The question remains open as to whether the silver-catalyzed methylenecyclopropane rearrangement proceeds via an argento-stabilized biradical or whether the reaction involves an argento-substituted allylic cation.

Electronic Properties of Triazoles. Experimental and Computational Determination of Carbocation and Radical-Stabilizing Properties

Three fluorobenzenes substituted with meta-triazole groups have been prepared, and 19F chemical shifts indicate that these triazole groups are all inductively electron-withdrawing in character, with the 1,5-triazole being the most electron-withdrawing. σ+ values for these three triazoles have also been determined from solvolysis rates of substituted cumyl trifluoroacetates. When substituted in the para-position, the 1,4 and the 2,4-triazoles are cation-stabilizing, whereas the 1,5-triazole is carbocation-destabilizing. γ+ values indicate that the 1,4 triazole group is cation-stabilizing relative to the phenyl group, albeit the 1,5 triazole is significantly destabilizing relative to phenyl. These studies all suggest that the 1,5-triazole group exerts a strong electron-withdrawing effect on carbocations that is not offset by a resonance effect. The three triazole groups all enhance the methylenecyclopropane rearrangement rate and are therefore radical stabilizers. The smallest stabilizing effect is seen for the 1,5-triazole, and this is attributed to the triazole group being twisted out of conjugation in the developing benzylic radical. Finally, the anionic triazole group is the most effective radical-stabilizing group. Computational studies indicate that these triazole groups all stabilize benzylic radicals by a spin delocalization mechanism.

Methylenecyclopropane Rearrangement as a Probe for Free Radical Substituent Effects. σ·Values for Potent Radical-Stabilizing Nitrogen-Containing Substituents

A series of nitrogen-containing 2-aryl-3,3-dimethylmethylenecyclopropanes have been prepared and rearrangement rates to the corresponding 2-arylisopropylidenecyclopropanes have been measured. These rates are dependent on the nature of the nitrogen-containing group in the para-position of the aryl group. Rearrangement rates have been used to calculate σ· values, which are a measure of the radical stabilizing ability of the substituent. Groups such as p-N=N-Bu-t, p-CH=N-Bu-t, p-NH2, p-CH=N-OH, and p-CH=N-OCH3, are "good" radical stabilizers. We have also classified groups such as p-CH=N-NMe2, p-N=N-Ph, p-N=N(O)-Bu-t, p-CH=N(O)-Bu-t, and p-CH=N-O- M+, which have an extraordinarily large radical stabilizing effect, as "Super Stabilizers". These substituents stabilize the transition state of the methylenecyclopropane rearrangement by extensive spin delocalization. In the case of the latter three substituents, nitroxyl type stabilization is proposed. Density functional calculations (B3LYP/6-31G*) have been carried out on a series of nitrogen-containing substituted benzylic radicals. Rates of the methylenecyclopropane rearrangement correlate with radical stabilization energies (ΔE) determined from an isodesmic reaction of substituted benzylic radicals with toluene. These calculations confirm substantial spin delocalization onto the nitrogen-containing substituents on the para-position of the benzylic radical.

Facile autoxidation of 2-(4-hydroxyphenyl)-3,3-dimethylmethylenecyclopropane. The radical stabilizing ability of the phenoxide group

(matrix presented). 2-(4-Hydroxyphenyl)-3,3-dimethylmethylenecyclopropane undergoes rapid reaction with O2 at room temperature to give a dioxolane. A chain mechanism involving ring opening of a phenoxy radical is proposed. Conversion of the tit

First synthesis, X-ray structure analysis and reactions of alkenyltriphenylbismuthonium salts

Treatment of triphenylbismuth difluoride with alkenyltrimethylsilanes 1 or trimethylsilyl cyanidealkenyltrialkylstannanes 3 in the presence of boron trifluoride-diethyl ether gave the corresponding alkenyltriphenylbismuthonium tetrafluoroborates 2 in moderate to good yields. An X-ray crystallographic analysis of the salt 2e confirmed the distorted tetrahedral geometry of the central bismuth atom. When treated with a sulfinate 5 or the thiolate 11, the salts 2 readily transferred both the vinyl and phenyl moieties to these nucleophiles to afford the sulfones 7-10 or the sulfides 12, 13, respectively. In the presence of a palladium catalyst, the salt 2e underwent the Heck-type reaction with ethyl acrylate 17 to afford the dienoate 18 and cinnamate 19 in moderate yields. Action of KOBut on the salt 2b yielded p-tolylacetylene 22, while a similar reaction with the salt 2e in the presence of the styrenes 23 gave the cyclopropanes 24. A Hammett study of the latter reaction has suggested a possible involvement of an alkylidenecarbene as the intermediate in these base-promoted reactions.

A Comparison of the Radical-Stabilizing Ability of Aromatic Groups. γ. Values for Aromatic Groups

A series of 15 2-aryl-3,3-dimethyl-1-methylenecyclopropanes, 1, have been prepared and thermally rearranged in C6D6 to the corresponding 2-aryl-1-isopropylidenecyclopropanes, 3.Rearrangement rates give a measure of the ability of various aromatic groups to stabilize the transition state leading to a biradical intermediate.The 4-pyridine N-oxide group was found to be the most effective of the aromatic groups in stabilizing the radical intermediate.This has been rationalized by considering the mode of spin delocalization in such radicals.Resonance interactions result in an intermediate which is stabilized due to nitroxide radical character.The 2-furanyl and 2-thienyl groups are also very effective radical stabilizing groups.Rearrangement rates of 1 were converted to γ. values, which are a quantitative measure of the relative abilities of various groups to stabilize free radicals.

THE EFFECT OF THE TRIFLUOROMETHYL GROUP ON THE METHYLENECYCLOPROPANE REARRANGEMENT

The CF3 group, in conjunction with an electron donor group, can enhance the rate of the methylenecyclopropane rearrangement.This is attributed to captodative radical stabilization of the intermediate biradical.

Methylenecyclopropane Rearrangement as a Probe for Free Radical Substituent Effects. ?. Values for Commonly Encountered Conjugating and Organometallic Groups

A series of 3-aryl-2,2-dimethylmethylenecyclopropanes, 8, with NO2, NMe2, vinyl, isopropenyl, phenyl, cyclopropyl, CH2SiMe3, SiMe3, SnMe3, , and HgCl substitution in the para position of the aromatic ring have been prepared.All rearrange thermally to the corresponding isopropylidenecyclopropanes 9 at rates that are substituent dependent.These commonly encountered substituents all enhance rearrangement rates relative to the unsubstituted analogue with p-NMe2 being the most effective.The rate enhancements are interpreted in terms of stabilization of the biradical intermediate by the para substituent.Rate data have allowed the assignment of ?. values for these groups, which have not been previously determined.The nitro group in the para position is also quite effective in increasing the rearrangement rate, which contrasts with the effect of this group on many other free radical reactions.Vinyl is somewhat more effective as a radical stabilizing group than is isopropenyl or phenyl, possibly due to steric interactions in the planar conformations necessary for conjugative stabilization by isopropenyl or phenyl.Trimethylsilyl,trimethylstannyl, and HgCl all enhance the methylenecyclopropane rearrangement rate, but only to a moderate extent.Boron containing substituents, where boron can act as an acceptor group, are among the more effective radical stabilizing groups, as implied by their effect on the rearrangement rate of 8.The cyclopropyl and CH2SiMe3 groups, which also enhance the rearrangement rate of 8 to a moderate extent, become even more effective radical stabilizing groups when present in conjunction with the carbethoxy group.These two conjugating groups are therefore capable of acting as donor groups in captodative radical stabilization.