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• 66312-03-6 2,3,4,5-Tetramethyltetracyclo<4.4.0.0^2,4.0^3,5>deca-7,9-dien-1,6-dicarbonsaeureanhydrid 
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• 95838-08-7 (3aα,4β,7β,7aα,8β,9β)-4,7,8,9-tetrahydro-2,4,7,8,9,10,11-heptamethyl-5,6-diphenyl-3a,7a<1',2'>-endo-cyclobut-4,7-methano-1H-isoindole-1,3,12(2H)-trione 
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• 17420-02-9 N-(2,6-dimethylphenyl)sulfinylamine 
• 31886-99-4 tetramethylcyclobutadiene*aluminum trichloride 

Relevant academic research and scientific papers

Valence Isomerizations, 18. - Valence Isomerizations of Persubstituted (CH)10 Systems

Within the synthesis of persubstituted dihydronaphthalenes, altogether nineteen octamethylbis(methoxycarbonyl)-substituted valence isomers have been isolated, and their structures and mutual relationships clarified.Compared to the unsubstituted parent compounds, there are remarkable differences.The same is true for seven valence-isomeric forms of permethylated (CH)10 hydrocarbons which correspond to diesters and are also presented in this article. - Keywords: Persubstituted (CH)10 systems / Photochemical and thermal isomerizations / Steric crowding / Valence isomerizations

Valence Isomerizations, 17. - Persubstituted cis-9,10-Dihydronaphthalenes and their Valence Isomerizations

The tricyclic diester 10 is available from 2-butyne in a six-step synthesis with an overall yield of 10percent.Thermolysis of 10 gives the bicyclic diester 11 which upon UV irradiation yields 12 as the first persubstituted cis-9,10-dihydronaphthalene.X-ray analysis of 12 shows the molecule considerably twisted along the central bond.In addition, the planes of the ester groups are at an angle of approximately 60 deg to the "planes" of the six-membered rings so that conjugation of the diene systems with the carbonyl functions is virtually interrupted, an effect which is reflected by the unusual spectroscopic properties of 12.The same structural features can be found in decamethyl-cis-9,10-dihydronaphthalene (16).When heated slightly, 12 is converted to the tetracyclic valence isomer 34.On reduction of 12 with diisobutylaluminium hydride both, dihydronaphthalene dicarbinol 25 as well as its unexpected positional isomer 26, are formed depending on the reaction conditions.Etherification of the reduction products with CH2N2/Et2O-BF3 furnishes a mixture of the three isomeric bis(methoxymethyl) compounds 31, 32, and 33.They can be separated by chromatography in the cold, but revert to the mixture of the three isomers at room temperature.We consider diradical 38 to be the intermediate of this intriguing valence isomerization. - Keywords: Molecular twisting / cis-9,10-Dihydronaphthalenes, persubstituted / Valence isomerizations

A NEW REAGENT FOR THE GENERATION OF TETRAMETHYLCYCLOBUTADIENE UNDER THERMAL OR PHOTOCHEMICAL CONDITIONS

A new, stable, easy to prepare synthetic equivalent for tetramethylcyclobutadiene is described.This reagent can be used under thermal or photochemical conditions and offers advantages over existing alternatives.

Benzvalene and Dewar Benzene Type Sulfinamides

The reaction of cyclobutadiene aluminum halide ? complexes with N-arylsulfinylamines leads, depending on the substitution pattern of the phenyl ring, to either bicyclic (Dewar benzene type) or tricyclic sulfinamides, the latter being formed via an intramolecular Friedel-Crafts reaction of an intermediate cyclobutenyl cation.A similar reaction of aluminum halide ? complex 1 with N-tert-butylsulfinylamine affords both a bicyclic and a tricyclic (benzvalene type) sulfinamide.

Small rings, 36. Attempts to Synthesize Tetramethyltetrahedrane from Alicyclic Precursors

Synthesis as well as the thermal and photochemical behaviour of compounds with ring skeletons 1 and 3 are described.Whereas the former are accessible by standard procedures the approach to the bicyclobutane derivatives is based on the isomerization of diester 1b into valence isomer 3b which can be achieved in good yield by SiO2 or Al2O3.There are only minor differences in the cleavage of the pairs 1/3 provoked by heating or photochemical excitation.This is even true for irradiations in argon at 10 K.Under those conditions anhydrides 1a and 3a form the samecharge transfer complex 28a between tetramethylcyclobutadiene and phthalic anhydride.A direct detection of tetramethyltetrahedrane using these means is not possible.

Small Rings, 35. Attempts to synthesize tetramethyltetrahedrane from heterocyclic precursors

By comparison of the photochemical behaviour of heterocycles 1 and 3 under matrix conditions it should be possible to prove the existence of tetramethyltetrahedrane (5).Whereas irradiation of 1 leads to the charge-transfer complex 32, the same is not true for 3 in spite of the fact that after warm-up the products, namely dimer 31 of tetramethylcylobutadiene (4) and tetramethylpyridazine (2), are identical in both series.Intermediate formation of tetramethyltetrahedrane is one but not the only way for mechanistic interpretation of the experimental findings.