2892-62-8

Basic information

• Product Name: Dibutyl squarate
• Synonyms: 3,4-DI-N-BUTOXY-3-CYCLOBUTEN-1,2-DIONE;3,4-DI-N-BUTOXY-3-CYCLOBUTENE-1,2-DIONE;3,4-DIBUTOXY-3-CYCLOBUTENE-1,2-DIONE;3,4-DIBUTOXYCYCLOBUT-3-ENE-1,2-DIONE;DIBUTYL SQUARATE;Di-n-butyl squarate~Squaric acid di-n-butyl ester;3,4-DIBUTOXY-3-CYCLOBUTENE-1,2-DIONE, 98 %;di-n-butyl squarate
• CAS NO: 2892-62-8
• Molecular Formula: C₁₂H₁₈O₄
• Molecular Weight: 226.27
• Product Categories: API intermediates;Cyclobutanes & Cyclobutenes;Simple 4-Membered Ring Compounds
• Mol File: 2892-62-8.mol
• Article Data: 13

Chemical Properties

• Boiling Point: 139 °C0.5 mm Hg(lit.)
• Flash Point: >230 °F
• Appearance: Clear colorless to yellow/Liquid
• Density: 1.047 g/mL at 25 °C(lit.)
• Vapor Pressure: 3.64E-05mmHg at 25°C
• Refractive Index: n20/D 1.494(lit.)
• Storage Temp.: Sealed in dry,Room Temperature
• Water Solubility: INSOLUBLE
• BRN: 1968189
• CAS DataBase Reference: Dibutyl squarate(CAS DataBase Reference)
• NIST Chemistry Reference: Dibutyl squarate(2892-62-8)
• EPA Substance Registry System: Dibutyl squarate(2892-62-8)

Safety Data

• Hazard Codes: Xn
• Statements: 36/37/38-42/43
• Safety Statements: 26-27-36/37/39-45
• WGK Germany: 3
• RTECS: GU1772066
• Hazardous Substances Data: 2892-62-8(Hazardous Substances Data)

Usage

Chemical Properties

clear colorless to yellow liquid

Uses

Different sources of media describe the Uses of 2892-62-8 differently. You can refer to the following data:
1. Squaric acid and its derivatives (Dibutyl squarate) are used in synthesis of pharmaceutical intermediates, squarylium dyes, and photoconducting squaraines.
2. 3,4-Dibutoxy-3-cyclobutene-1,2-dione was used in the synthesis of novel semisquarylium dye, useful for highly selective Hg2+ sensing in aqueous media. It was also employed in the synthesis of 3-butoxy-4-(1,3,3-trimethyl-2,3-dihydro-1H-2-indolylidenemethyl)-3-cyclobutene-1,2-dione, intermediate for the synthesis of squaryl dyes.

Definition

ChEBI: A cyclic ketone and diether that is a dibutyl ether derivative of squaric acid.

General Description

3,4-Dibutoxy-3-cyclobutene-1,2-dione is the dialkyl ester of squaric acid.

InChI:InChI=1/C12H18O4/c1-3-5-7-15-11-9(13)10(14)12(11)16-8-6-4-2/h3-8H2,1-2H3

Synthetic route

Tributyl orthoformate (588-43-2) + squaric acid (2892-51-5) + butan-1-ol (71-36-3) → 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8)

Conditions	Yield
for 23.5h; Heating;	97%

squaric acid (2892-51-5) + butan-1-ol (71-36-3) → 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8)

Conditions	Yield
In benzene Heating; Dean-Stark trap;	95%
In benzene for 3h; Heating;	86%
for 3h; Reflux;	74%

2,3,4,4-tetrachloro-cyclobut-2-en-1-one (3200-96-2) + butan-1-ol (71-36-3) → 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8)

Conditions	Yield
Heating;	68%

BARBITURIC ACID (67-52-7) + 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + triethylamine (121-44-8) → triethylammonium 5-(2-hydroxy-3,4-dioxocyclobut-1-en-1-yl)-2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-olate

Conditions	Yield
In ethanol at 20℃; for 0.333333h;	100%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 6-ethoxy-N-methyl-2-quinaldinium iodide (63151-41-7) → C21H23NO4 (797039-87-3)

Conditions	Yield
With triethylamine In butan-1-ol at 25℃; for 12h;	98%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + benzylamine (100-46-9) → 3-(benzylamino)-4-butoxycyclobut-3-ene-1,2-dione

Conditions	Yield
In dichloromethane at 0 - 20℃;	98%
In dichloromethane at 20℃;

N-(7-chloroquinolin-4-yl)ethylenediamine (5407-57-8) + 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) → C26H22Cl2N6O2 (1487428-79-4)

Conditions	Yield
In methanol for 12h; Reflux;	97%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (2'-aminoethylamido)carbonylpentyl α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranoside → 1-[(2'-aminoethylamido)carbonylpentyl α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranoside]-2-butoxycyclobutene-3,4-dione

Conditions	Yield
With sodium hydrogencarbonate In ethanol; water at 21℃; pH=8;	96%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (R)-1,2,2-trimethylpropylamine (3850-30-4, 22526-47-2, 59367-75-8, 66228-31-7) → (R)-3-butoxy-4-(1,2,2-trimethyl-propylamino)-cyclobut-3-ene-1,2-dione

Conditions	Yield
In tetrahydrofuran; ethanol at 20℃; for 65h; Condensation;	95%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 6-hydroxy-4-methyl-N-methyl-quinaldinium iodide (1346893-02-4) → C20H21NO4 (1346893-11-5)

Conditions	Yield
With triethylamine In butan-1-ol at 25℃; for 12h;	95%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 1-(2-hydroxyethyl)-2-methylquinoline-1-ium iodide salt (64170-00-9) → C20H21NO4 (1346893-09-1)

Conditions	Yield
With triethylamine In butan-1-ol at 25℃; for 12h;	95%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 6-hydroxy-N-methyl-2-quinaldinium iodide → C19H19NO4 (797039-86-2)

Conditions	Yield
With triethylamine In butan-1-ol at 25℃; for 12h;	95%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + malononitrile (109-77-3) → sodium 1,2-bis(dicyanomethylene)cyclobutane-3,4-dione

Conditions	Yield
With sodium; butan-1-ol at 20℃; for 0.166667h;	94%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 6-(dimethylamino)-1,2-dimethylquinolin-1-ium iodide → C21H24N2O3 (1346893-06-8)

Conditions	Yield
With triethylamine In butan-1-ol at 25℃; for 12h;	94%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (2'-aminoethylamido)carbonylpentyl α-D-mannopyranosyl(1→3)-4,6-dideoxy-4-formamido-α-D-mannopyranoside → 1-[(2'-aminoethylamido)carbonylpentyl α-D-mannopyranosyl(1→3)-4,6-dideoxy-4-formamido-α-D-mannopyranoside-2-butoxycyclobutene-3,4-dione]

Conditions	Yield
With sodium hydrogencarbonate In ethanol; water at 21℃; pH=8;	94%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (2'-aminoethylamido)carbonylpentyl 4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→3)-4,6-dideoxy-4-formamido-α-D-mannopyranoside → 1-[(2'-aminoethylamido)carbonylpentyl 4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→3)-4,6-dideoxy-4-formamido-α-D-mannopyranoside]-2-butoxycyclobutene-3,4-dione

Conditions	Yield
With sodium hydrogencarbonate In ethanol; water at 21℃; for 0.5h; pH=8; Heating;	92%

2-(ethylthio)ethylamine hydrochloride (36489-03-9) + 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) → 3,4-bis{[2-(ethylsulfanyl)ethyl]amino}cyclobut-3-ene-1,2-dione

Conditions	Yield
In diethyl ether at 20℃; for 1h;	92%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 3-bromopropylamine hydrochloride (5003-71-4) → 1-butoxy-2-(3-bromopropylamino)-1-cyclobutene-3,4-dione (120356-93-6)

Conditions	Yield
With sodium hydroxide In methanol; water	91.8%
With sodium hydroxide In methanol; water	84%
With sodium hydroxide In methanol; toluene

bromopropylamine base + 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 3-bromopropylamine hydrochloride (5003-71-4) → 1-butoxy-2-(3-bromopropylamino)-1-cyclobutene-3,4-dione (120356-93-6)

Conditions	Yield
With sodium hydroxide In methanol; water	91.8%
With sodium hydroxide In methanol; water	84%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + phenyllithium (591-51-5) → 2,3-dibutoxy-1,4-diphenyl-1,4-butanedione

Conditions	Yield
In diethyl ether for 0.25h; Ambient temperature;	91%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + N-isopropylhydroxylamine hydrochloride (50632-53-6) → 3-butoxy-4-(hydroxy-isopropyl-amino)-cyclobut-3-ene-1,2-dione (1078060-51-1)

Conditions	Yield
With potassium hydroxide In methanol at 20℃; for 5h;	91%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (2'-aminoethylamido)carbonylpentyl α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→3)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranoside → 1-[(2'-aminoethylamido)carbonylpentyl α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→3)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranoside 2-butoxycyclobutene-3,4-dione]

Conditions	Yield
With sodium hydrogencarbonate In ethanol; water at 21℃; pH=8;	91%

3-methylthio-1-propanamine (4104-45-4) + 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) → 3,4-bis{[3-(methylsulfanyl)propyl]amino}cyclobut-3-ene-1,2-dione

Conditions	Yield
In diethyl ether at 20℃; for 1h;	91%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + 3-diethylaminophenol (91-68-9) → (E)-2-(4-(diethylamino)-2-hydroxyphenyl)-4-(4-(diethyliminio)-2-hydroxycyclohexa-2,5-dien-1-ylidene)-3-oxocyclo but-1-en-1-olate (68842-66-0)

Conditions	Yield
With sulfuric acid; water In butan-1-ol at 125 - 130℃;	90%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + primaquine diphosphate (63-45-6) → C34H40N6O4 (1487428-85-2)

Conditions	Yield
Stage #1: primaquine diphosphate With triethylamine In methanol at 20℃; for 0.5h; Inert atmosphere; Stage #2: 3,4-dibutoxy-3-cyclobutene-1,2-dione In methanol for 48h; Inert atmosphere; Reflux;	89%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (2-aminoethylamido)carbonylpentyl β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-β-D-glucopyranosyl-(1→3)-β-D-glucopyranoside → 1-[(2-aminoethylamido)carbonylpentyl β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-β-D-glucopyranosyl-(1→3)-β-D-glucopyranoside]-2-butoxycyclobutene-3,4-dione

Conditions	Yield
With sodium hydrogencarbonate In ethanol; water for 0.5h; pH=8;	89%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (2'-aminoethylamido)carbonylpentyl 4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranoside → 1-[(2'-aminoethylamido)carbonylpentyl 4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranosyl-(1→2)-4,6-dideoxy-4-formamido-α-D-mannopyranoside]-2-butoxycyclobutene-3,4-dione

Conditions	Yield
With sodium hydrogencarbonate In ethanol; water at 21℃; for 0.5h; pH=8; Heating;	88%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + tert-butylamine (75-64-9) → 3-butoxy-4-(tert-butylamino)-cyclobut-3-ene-1,2-dione (202520-56-7)

Conditions	Yield
In tetrahydrofuran at 20℃; for 71h; Condensation;	87%
In dichloromethane at 20℃; for 20h;	74%
In dichloromethane at 20℃;

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + (1R,2S)-2-Amino-1,2-diphenylethanol (23190-16-1) → 3-butoxy-4-[(1'S,2'R)-(2'-hydroxy-1',2'-diphenylethyl)amino]-3-cyclobutene-1,2-dione

Conditions	Yield
With triethylamine In ethanol at 20℃; for 24h;	87%

3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) + C39H56N2O6 → C28H50N2O9

Conditions	Yield
Stage #1: C39H56N2O6 With trifluoroacetic acid at 20℃; for 0.333333h; Stage #2: 3,4-dibutoxy-3-cyclobutene-1,2-dione With N-ethyl-N,N-diisopropylamine In chloroform Reflux;	86.8%

2-methyl-2-butylamine (594-39-8) + 3,4-dibutoxy-3-cyclobutene-1,2-dione (2892-62-8) → 3-butoxy-4-(1,1-dimethyl-propylamino)-cyclobut-3-ene-1,2-dione (201012-44-4)

Conditions	Yield
In tetrahydrofuran at 20℃; for 19.5h; Condensation;	86%

Upstream product

• 588-43-2 Tributyl orthoformate 
• 2892-51-5 squaric acid 
• 71-36-3 butan-1-ol 
• 3200-96-2 2,3,4,4-tetrachloro-cyclobut-2-en-1-one 

Downstream Products

• 82930-30-1 squaraine 
• 1352129-14-6 C₃₀H₃₅N₃O₇S 
• 1352129-17-9 C₃₁H₃₇N₃O₇S 
• 1352129-11-3 C₂₃H₂₉N₃O₇S 
• 645387-45-7 (3R,4R)-3,4-diphenyl-2,5-diazabicyclo[4.2.0]oct-1⁽⁶⁾-ene-7,8-dione 
• 1255088-66-4 (3R,4R,11R,12R)-3,4,11,12-tetraphenyl-2,5,10,13-tetraazatricyclo[12.2.0.06,9]hexadeca-1⁽¹⁴⁾,6⁽⁹⁾-diene-7,8,15,16-tetraone 
• 1078060-48-6 3-(benzyl-hydroxy-amino)-4-butoxy-cyclobut-3-ene-1,2-dione 
• 335646-03-2 3-butoxy-4-[(2'S)-2'-(diphenylhydroxymethyl)pyrrolidino]-3-cyclobutene-1,2-dione 
• 334833-59-9 3-butoxy-4-[(1'R,2'S)-(2'-hydroxy-1',2'-diphenylethyl)amino]-3-cyclobutene-1,2-dione 
• 43134-09-4 bis[4-(dimethylamino)phenyl]squaraine 

Relevant articles and documents

An efficient general synthesis of squarate esters

An efficient and general method for the synthesis of alkyl squarates is presented. This involves the reactions of squaric acid with the desired alcohol in the presence of an orthoformate. This was applicable for the synthesis of dimethyl-, diethyl-, diisopropyl, di-n-butyl and di-t-butyl squarates in yields ranging from 77-97%. It is a convenient and safe method that can be accomplished on a multigram scale.

Synthesis, spectroscopic characterization and biological evaluation of unsymmetrical aminosquarylium cyanine dyes

New unsymmetrical aminosquarylium cyanine dyes were synthesized and their potential as photosensitizers evaluated. New dyes, derived from benzothiazole and quinoline, were prepared by nucleophilic substitution of the corresponding O-methylated, the key intermediate that was obtained by methylation with CF3SO3CH3 of the related zwitterionic unsymmetrical dye, with ammonia and methylamine, respectively. All three news dyes herein described displayed intense and narrow bands in the Vis/NIR region (693–714?nm) and their singlet oxygen formation quantum yields ranged from 0.03 to 0.05. In vitro toxicity, in Caco-2 and HepG2 cells, indicated that dark toxicity was absent for concentrations up to 5?μM (for the less active dye) or up to 1?μM (for the two more active dyes). The three dyes present potential as photosensitizers, differing in irradiation conditions and period of incubation in the presence of irradiated dye. The less active dye needs a longer irradiation period to exhibit phototoxicity which is only evident after longer period of contact with cells (24?h). However, the remaining two more active dyes produce higher phototoxicity, even at shorter incubation periods (1?h), with shorter irradiation time (7?min). Although in different extents, these dyes show promising in vitro results as photosensitizers.

Electro-optical Properties of Neutral and Radical Ion Thienosquaraines

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