33284-11-6

Usage

Family

Pentalene family

Structure

Cyclic hydrocarbon compound with a five-membered ring, two double bonds, and one hydrogen

Reactivity

Unique due to its structure

Applications

Primarily used as a building block in organic synthesis, particularly in medicinal chemistry

Potential

Studied for use as a precursor in the synthesis of complex organic molecules and in materials science

Challenges

Reactivity and stability present difficulties in handling and storage, making it an area of ongoing research and development

Upstream product

• 35434-64-1 tetracyclo<3.3.0.0^2,4.0^3,6>oct-7-ene 
• 629-20-9 1,3,5,7-cyclooctatetraene 
• 694-87-1 benzocyclobutene 
• 102935-87-5 4-acetoxytricyclo<4.3.1^6,9.0>dec-2-ene 
• 122902-50-5 5-(cyclopentadienylidenemethyl)bicyclo<2.2.1>hept-2-ene 
• 692-50-2 hexafluoro-2-butyne 
• 80976-46-1 sodium salt of bicyclo<3.2.1>octa-2,6-dien-4-one p-toluenesulfonylhydrazone 
• 30294-54-3 dihydropentalene 
• 277-10-1 cubane 

Downstream Products

• 140438-53-5 anti-3,5,7,12,14,16-hexaaza-5,14-diphenylhexacyclo<9.5.1.1^1,9.0^2,8.0^3,7.0^12,16>octadec-9-ene-4,6,13,15-tetraone 
• 140438-57-9 3,4,9,10-tetraazatetracyclo<6.2.1.1^1,6.0^2,5>dodeca-3,9-diene 
• 140438-60-4 3,4-diazatetracyclo<6.1.1^2,5.0^2,7.0>dec-3-ene 
• 30294-54-3 dihydropentalene 

Relevant academic research and scientific papers

New Pathways to Precursors of Pentalene

Pentalene dimers 2 and 3 are easily available in moderate yields by CuCl2-induced oxidative coupling of dilithium-pentalenediide (5) (Scheme 1).On the other hand, NBS bromination of 1,5-dihydropentalene (4) or of 1,2-dihydropentalene (8) gives unstable 1-bromo-1,2-dihydropentalene (9), while subsequent in-situ elimination with Et3N exclusively gives syn-cis-pentalene dimer 2 in moderale yields (Scheme3).NMR-Spectroscopic evidence for compounds 2. 3. and 9 is presented, and mechanistic alternatives for the formation of pentalene dimers 2 and 3 are discussed.

Ein effizienter Zugang zu 1,5-Dihydropentalen und 2-Methyl-1,5-dihydropentalen aus Acrolein und Methacrolein

Acrolein and methacrolein can be converted into 1,5-dihydropentalene and its 2-methyl derivative, respectively, by a simple, three-step process. Cycloaddition of the aldehydes with cyclopentadiene affords 5-formyl-2-norbornenes which readily undergo condensation with cyclopentadiene to give 5-(cyclopentadienylidenemethyl)-2-norbornenes.These protected 6-vinylpentafulvenes undergo retro-cleave to cyclopentadiene and the 1,5-dihydropentalenes on vacuum flash thermolysis.

PHOTOCHEMISTRY OF BENZOCYCLOBUTENE

Photolysis of benzocyclobutene (1) in pentane solution at 254 nm yields 1,2-dihydropentalene (2) and 1,5-dihydropentalene (3) as the major isomeric products; formation of 2 and 3 is consistent with a "prebenzvalene"-carbene rearrangement mechanism.

Isomerization of Dihydropentalenes and Reaction with Tetracyanoethylene

The six isomeric dihydropentalenes 1-6 are connected by various H-shifts (Scheme 1), which are investigated in gas phase pyrolyses.Thermodynamic control leads irreversibly from equilibria between 1-6 to styrene (15) via 1-vinylfulvene (14).The catalytic isomerization 1,5-DHP (4) 1,2-DHP (1) at room temperature is of special preparative interest.Reaction of the dihydropentalenes with tetracyanoethylene yields the adduct 24 of 1, the adducts 25 and 26 of 3 and 5, respectively, and the double adduct 22 of 4. 2 and 6 cannot be trapped with TCNE under flash pyrolysis conditions.

Dihydropentalenes

Applying the MNDO method the enthalpies of formation and the frontier orbitals of the six isomeric dihydropentalenes 1-6 have been calculated .An easy preparative access for the energy lower systems 1-4 is provided by the thermolysis of cyclooctatetraene (8) performed under different conditions and by different workup 1-4 were characterized by 1H- and 13C-NMR spectroscopy.

A Simple Preparation of 1,2-Dihydropentalene from Cyclooctatetraene

Flash thermolysis of cyclooctatetraene leads to a mixture of four isomeric dihydropentalenes 1,3,4 and 5.Catalytic hydrogen transfer on basic alumina or silica gel furnishes pure 1,2-dihydropentalene (1).

A CONVENIENT PREPARATIVE METHOD FOR THE SYNTHESIS OF 1,5-DIHYDROPENTALENE

A new preparative method was developed for the three-stage synthesis of 1,5-dihydropentalene.The method makes it possible to obtain the product from the cyclopentadiene dimer with an overall yield of 35-40percent.

The Pyrolysis of Cubane; an Example of a Thermally Induced Hot Molecule Reaction

The pressure dependence of the product distribution of cubane pyrolysis supports a mechanism involving cyclo-octatetraene formed in a highly vibrationally excited state through the release of ring strain energy.

MECHANISM OF THE THERMAL CONVERSION OF TETRACYCLO(3.3.0.02,4.03.6)OCT-7-ENE INTO DIHYDROPENTALENES

One of a number of possible mechanisms has been established for the title reaction.

Srtructure and Reactivity of Bicycloocta-2,6-dien-4-ylidene and Bicyclooct-2-en-4-ylidene. Nucleophilicity of Vinylcarbenes

Carbocyclic carbenes, bicycloocta-2,6-dien-4-ylidene (1) and bicyclooct-2-en-4-ylidene (2), were generated by photolysis of the corresponding diazo compounds, 6 and 10, which were prepared by careful vacuum pyrolysis of the sodium salts of t