1121-15-9

Basic information

• Product Name: 3,4-dimethylcyclobut-3-ene-1,2-dione
• Synonyms: 3,4-Dimethyl-3-cyclobutene-1,2-dione; 3-Cyclobutene-1,2-dione, 3,4-dimethyl-
• CAS NO: 1121-15-9
• Molecular Formula: C₆H₆O₂
• Molecular Weight: 110.1106
• Mol File: 1121-15-9.mol
• Article Data: 7

Chemical Properties

• Boiling Point: 178.9°C at 760 mmHg
• Flash Point: 59.5°C
• Density: 1.18g/cm³
• Vapor Pressure: 0.965mmHg at 25°C
• Refractive Index: 1.506
• CAS DataBase Reference: 3,4-dimethylcyclobut-3-ene-1,2-dione(CAS DataBase Reference)
• NIST Chemistry Reference: 3,4-dimethylcyclobut-3-ene-1,2-dione(1121-15-9)
• EPA Substance Registry System: 3,4-dimethylcyclobut-3-ene-1,2-dione(1121-15-9)

Safety Data

• Hazardous Substances Data: 1121-15-9(Hazardous Substances Data)

Upstream product

• 917-54-4 methyllithium 
• 5222-73-1 3,4-dimethoxy-3-cyclobutene-1,2-dione 
• 124175-62-8 3-(tert-butoxy)-4-methyl-cyclobut-3-ene-1,2-dione 
• 91359-03-4 2,2-Dichloro-3,4-dimethyl-3-phenylsulfanyl-cyclobutanone 
• 72284-72-1 4,4-Dichloro-2,3-dimethyl-2-cyclobuten-1-one 
• 114094-79-0 4-(tert-butyldimethylsiloxy)-2,3-bis(1-methylethoxy)-4-methylcyclobut-2-en-1-one 
• 114094-61-0 2,3-bis(1-methylethoxy)-4-hydroxy-4-methylcyclobut-2-en-1-one 
• 109609-84-9 2,3-dimethyl-buta-1,3-diene-1,4-dione 
• 917-64-6 methyl magnesium iodide 
• 5231-87-8 3,4-diethoxy-3-cyclobuten-1,2-dione 
• 75-16-1 methylmagnesium bromide 
• 114094-88-1 4-(tert-butyldimethylsiloxy)-2,3-bis(1-methylethoxy)-1,4-dimethylcyclobut-2-en-1-ol 
• 91359-07-8 2-Chloro-3,4-dimethyl-4-phenylsulfanyl-cyclobut-2-enone 

Downstream Products

• 168916-97-0 4-acetoxy-2,3-dimethyl-4-[4'-(tri-n-butylstannyl)phenyl]-2-cyclobutenone 
• 245342-69-2 N-benzyl-N-[3-(1-hydroxy-2,3-dimethyl-4-oxocyclobut-2-enyl)prop-2-ynyl]-3-p-tolylacrylamide 
• 30685-12-2 5-n-butyl-2,3-dimethylcyclohexa-2,5-diene-1,4-dione 
• 130352-47-5 4-C₂Me-4-hydroxy-3-methyl-2-methyl-2-cyclobuten-1-one 
• 25893-85-0 2,3-diethyl-5,6-dimethylcyclohexa-2,5-diene-1,4-dione 
• 59240-58-3 2,3-dimethyl-7-(2,4,6-trimethyl-phenyl)-5,8-dioxa-6-aza-spiro[3.4]octa-2,6-dien-1-one 
• 59208-27-4 1',5'-dimethyl-3,4',3''-tris-(2,4,6-trimethyl-phenyl)-dispiro[[1,4,2]dioxazole-5,6'-(2-oxa-3-aza-bicyclo[3.2.0]hept-3-ene)-7',5''-[1,4,2]dioxazole] 
• 59240-61-8 11,12-dimethyl-3,9-bis-(2,4,6-trimethyl-phenyl)-1,4,7,10-tetraoxa-2,8-diaza-dispiro[4.0.4.2]dodeca-2,8,11-triene 
• 130352-45-3 4-ethynyl-4-hydroxy-3-methyl-2-methyl-2-cyclobuten-1-one 
• 102808-45-7 4-hydroxy-4-phenyl-2,3-dimethylcyclobutenone 
• 1271-55-2 acetylferrocene 
• 478366-69-7 5-((ferrocenyl)(methoxy)methylene)-3,4-dimethyl-2(5H)-furanone 

Relevant articles and documents

Four-Electron Electrocyclic Ring-Opening/Intermolecular [4+2] Cycloadditions of α-Hydroxycyclobutenones: Stereoselective Synthesis of Multiple Substituted δ-Lactams

A four-electron electrocyclic ring-opening/intermolecular [4+2] cycloaddition of α-hydroxycyclobutenones is reported. The reaction represents the first example for the intermolecular cycloaddition of the extensively studied enol-ketene intermediate, and provides a new synthetic route to multiply substituted δ-lactams in high stereoselectivity.

Generation of 1,2-bisketenes from cyclobutene-1,2-diones by flash photolysis and ring closure kinetics

The interconversion of cyclobutene-1,2-diones (1) and 1,2-bisketenes (RC-C-O)2 has been surveyed for different combinations of substituents R = H, Me, t-Bu, Ph, Me3Si, CN, Cl, Br, R1O, alkynyl, and PhS. The bisketenes 2 have been generated by flash photolysis, and the kinetics of their conversion to 1 have been studied by time-resolved infrared and ultraviolet spectroscopy. The rate constants of the ring closure of 2 are correlated by the ketene stabilization parameters (SE) and with calculated barriers. The rate constant of ring closure of the di-tert-butyl bisketene 2g to cyclobutenedione 1g is only 40 times smaller than for the dimethyl analogue, showing a rather modest steric barrier. The quinoketene 2s has a fast rate of ring closure, but not as fast as anticipated on the basis of calculated geometric and thermodynamic factors. A lag in the attainment of aromatic stabilization in the transition structure for ring closure is a possible cause of this diminished reactivity.

An Improved Method for the Synthesis of Substituted Cyclobutenediones

Practical and high yielding routes to substituted cyclobutenediones are described. 3,4-Bis(1-methylethoxy)cyclobut-3-ene-1,2-dione (diisopropyl squarate), a stable, crystalline derivative of squaric acid, was easily prepared by refluxing squaric acid in 2