88-58-4

Basic information

• Product Name: 2,5-Di-tert-butylhydroquinone
• Synonyms: BHQ;DBHQ;Dibutylhydroquinone;DI-TERT-BUTYL HYDROQUINONE(2,5-);DI-T-BUTYLHYDROQUINONE;BUTYLHYDROQUINONE-TERT;2,5-BIS(2-METHYL-2-PROPYL)-1,4-BENZENEDIOL;2,5-DI-TERT-BUTYL-1,4-HYDROQUINONE
• CAS NO: 88-58-4
• Molecular Formula: C₁₄H₂₂O₂
• Molecular Weight: 222.32
• EINECS: 201-841-8
• Product Categories: Industrial/Fine Chemicals;Anthraquinones, Hydroquinones and Quinones;Organic Building Blocks;Oxygen Compounds;Polyols;Calcium signaling;Signalling
• Mol File: 88-58-4.mol
• Article Data: 66

Chemical Properties

• Melting Point: 216-218 °C(lit.)
• Boiling Point: 321°C
• Flash Point: 216 °C
• Appearance: Light beige to pink-beige/Crystalline Powder
• Density: 1,07 g/cm3
• Vapor Pressure: 6.6E-05mmHg at 25°C
• Refractive Index: 1.4576 (estimate)
• Storage Temp.: Store at RT
• Solubility: almost transparency in Methanol
• PKA: 11.89±0.23(Predicted)
• Water Solubility: 3.8mg/L at 20℃
• Stability: Stable. Incompatible with oxidizing agents.
• BRN: 2049542
• CAS DataBase Reference: 2,5-Di-tert-butylhydroquinone(CAS DataBase Reference)
• NIST Chemistry Reference: 2,5-Di-tert-butylhydroquinone(88-58-4)
• EPA Substance Registry System: 2,5-Di-tert-butylhydroquinone(88-58-4)

Safety Data

• Hazard Codes: Xi,Xn
• Statements: 36/37/38-22
• Safety Statements: 26-24/25
• WGK Germany: 3
• RTECS: MX5160000
• TSCA: Yes
• Hazardous Substances Data: 88-58-4(Hazardous Substances Data)

Usage

Chemical Properties

cream or pale brown solid

Uses

2,5-Di-tert-butylhydroquinone is the oxidation substrate used to measure the catalytic activity of the copper(II) enzyme-like catalysts.

Definition

ChEBI: A member of the class of hydroquinones that is benzene-1,4-diol substituted by tert-butyl groups at position 2 and 5.

General Description

Mobilizes Ca2+ specifically from the Ins(1,4,5)P3-sensitive Ca2+ stores by inhibiting microsomal and sarcoplasmic reticulum Ca2+-ATPase activity. Does not affect mitochondrial Ca2+ fluxes or plasma membrane Ca2+/Mg2+ ATPase activity. Useful for the study of endomembrane Ca2+ stores and plasma membrane Ca2+ permeability pathways.

Biological Activity

A selective inhibitor of endoplasmic reticulum Ca 2+ -ATPase.

Biochem/physiol Actions

2,5-Di-tert-butylhydroquinone specifically inhibits the sarcoplasmic reticulum (SR) Ca2+ uptake in the rat ventricle.

Purification Methods

Crystallise the hydroquinone from *C6H6 or AcOH. [Beilstein 6 III 4741.]

references

[1]. hasséssian h, vaca l, kunze dl. blockade of the inward rectifier potassium current by the ca(2+)-atpase inhibitor 2',5'-di(tert-butyl)-1,4-benzohydroquinone (bhq). br j pharmacol, 1994, 112(4): 1118-1122.[2]. fusi f, gorelli b, valoti m, et al. effects of 2,5-di-t-butyl-1,4-benzohydroquinone (bhq) on rat aorta smooth muscle. eur j pharmacol, 1998, 346(2-3): 237-243.[3]. fusi f, saponara s, gagov h, et al. 2,5-di-t-butyl-1,4-benzohydroquinone (bhq) inhibits vascular l-type ca(2+) channel via superoxide anion generation. br j pharmacol, 2001, 133(7): 988-996.[4]. jan cr, ho cm, wu sn, et al. mechanism of rise and decay of 2,5-di-tert-butylhydroquinone-induced ca2+ signals in madin darby canine kidney cells. eur j pharmacol, 1999, 365(1): 111-117.

InChI:InChI=1/C14H22O2/c1-13(2,3)9-7-12(16)10(8-11(9)15)14(4,5)6/h7-8,15-16H,1-6H3

Synthetic route

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + C72H116Fe4S8(3-)*2C16H36N(1+) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + C72H116Fe4S8(2-)*2C16H36N(1+)

Conditions	Yield
With [hydrogen(diethyl ether)][tetra[3,5-bis(trifluoromethyl)phenyl]borate]	A 100% B 100%

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + C39H17F33Fe4S8(3-)*2C16H36N(1+) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + C39H17F33Fe4S8(2-)*2C16H36N(1+)

Conditions	Yield
With [hydrogen(diethyl ether)][tetra[3,5-bis(trifluoromethyl)phenyl]borate]	A 65% B 100%

t-butyl bromide (507-19-7) + hydroquinone (123-31-9) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
silica gel In tetrachloromethane at 70℃; for 24h; Product distribution; addition of Na2CO3;	92%
With sodium carbonate; silica gel In tetrachloromethane at 70℃; for 24h;	92%

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
With 2,5-dihydrotoluene; trifluoroacetic acid In toluene at 30℃; for 15h; Solvent; Temperature; Reagent/catalyst;	90%
With boron trifluoride diethyl etherate; prenyl tributylstannane In dichloromethane at -78℃;	88%
With sodium dithionite In solid	85%

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + thiol + C47H72Fe4NS7(1-) → {Fe4S4(S-2,4,6-(i-Pr)3C6H2)4}(1-) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
With 2,4,6-tri-tert-butylphenoxyl	A 50% B 90%

{Fe4S4(S-2,4,6-(i-Pr)3C6H2)4}(3-) (96455-63-9) + 2,5-di-tert-butyl-p-benzoquinone (2460-77-7) → {Fe4S4(S-2,4,6-(i-Pr)3C6H2)4}(2-) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
With [hydrogen(diethyl ether)][tetra[3,5-bis(trifluoromethyl)phenyl]borate]	A 80% B 85%

methanesulfonic acid 2,5-di-tert-butyl-4-methanesulfonyloxyphenyl ester → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
With lithium diisopropyl amide In tetrahydrofuran at 0℃; for 0.5h;	70%

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + trans-2-butenyltrimethylstannane (3200-73-5) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 2-(2-butenyl)-5-tert-butylhydroquinone (74785-31-2)

Conditions	Yield
With boron trifluoride diethyl etherate In dichloromethane at -78℃;	A 56% B n/a

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + triisobutylaluminum (100-99-2) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 2,5-di-t-butyl-1-isobutylbenzene (77501-99-6) + 2-t-butyl-5-isobutyl-1,4-dihydroxybenzene (127558-27-4)

Conditions	Yield
In benzene for 10h; Heating;	A 32% B 16% C 52%
In benzene for 10h; Mechanism; Heating;	A 32 % Chromat. B 16 % Chromat. C 52 % Chromat.

hydroquinone (123-31-9) + tert-butyl alcohol (75-65-0) → t-butyl phenyl ether (6669-13-2) + 2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + tert-butylhydroquinone (1948-33-0)

Conditions	Yield
With porous pillared-zirconium phosphate functionalized with methyl group In 5,5-dimethyl-1,3-cyclohexadiene at 150℃; for 4h; Reagent/catalyst; Autoclave;	A n/a B n/a C n/a D 48.8%
With perfluorosulfonicacid-functionalized carbon nanotubes (PFSA-CNT-0.5) In 5,5-dimethyl-1,3-cyclohexadiene for 4h; Catalytic behavior; Reagent/catalyst; Autoclave;

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + allyltributylstanane (24850-33-7) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 2-(1,1-dimethylethyl)-5-(2-propenyl)-1,4-benzenediol (73685-60-6)

Conditions	Yield
With boron trifluoride diethyl etherate In dichloromethane at -78℃;	A 35% B 36%

hydroquinone (123-31-9) + tert-butyl alcohol (75-65-0) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
With sulfuric acid; acetic acid

hydroquinone (123-31-9) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
With aluminium at 150℃; anschliessendes Erhitzen mit Isobutylen auf 240grad;

2,5-di-tert-butyl-p-benzoquinone (2460-77-7) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 2,5-di-t-butyl-1-isobutylbenzene (77501-99-6) + 2-t-butyl-5-isobutyl-1,4-dihydroxybenzene (127558-27-4)

Conditions	Yield
With triisobutylaluminum In benzene for 10h; Heating;	A 32 % Chromat. B 16 % Chromat. C 52 % Chromat.

hydroquinone (123-31-9) + isobutene (115-11-7) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 2-t-Butyl-4-t-butoxyphenol (2467-52-9) + tert-butylhydroquinone (1948-33-0)

Conditions	Yield
With Amberlyst IR120 H(1+) In diethyl ether Ambient temperature;

ethanol (64-17-5) + tertiary butyl chloride (507-20-0) + hydroquinone (123-31-9) + ZnCl2 → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

2,5-Di-tert-butyl-4-hydroxy-phenoxyl (124700-28-3) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4)

Conditions	Yield
With 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol In benzene at 19.85℃; Equilibrium constant; Thermodynamic data; Further Variations:; Solvents;

tert-butyl methyl ether (1634-04-4) + hydroquinone (123-31-9) → 2,6-di-tert-butyl-4-hydroxyphenol (2444-28-2) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 4-(tert-butoxy)phenol (2460-87-9) + tert-butylhydroquinone (1948-33-0)

Conditions	Yield
With 3-(4-sulfobutylamino)propylsilanized MCM-41 In nitrobenzene at 150℃; for 0.133333h; Catalytic behavior; Concentration; Friedel-Crafts Alkylation; Microwave irradiation; Green chemistry; chemoselective reaction;

acid blue 5 → 5-methyl-2-hydroxyacetophenone (1450-72-2) + 4-hydroxybutanoic acid (591-81-1) + malic acid (617-48-1) + 2-hydroxyacrylic acid (19071-34-2) + 1,5-dihydroxynaphthalene (83-56-7) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 1-aminoethenol

Conditions	Yield
With dihydrogen peroxide pH=3; Kinetics; Reagent/catalyst; Concentration; pH-value;

hydroquinone (123-31-9) + tert-butyl alcohol (75-65-0) → 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + tert-butylhydroquinone (1948-33-0)

Conditions	Yield
With phosphoric acid In toluene at 70 - 105℃;

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 2,5-di-tert-butyl-p-benzoquinone (2460-77-7)

Conditions	Yield
With benzyltrimethylammonium tribromide In water; acetic acid for 0.166667h; Ambient temperature;	100%
With 3-[3,6-dioxo-2-(pyridinium-1-yl)cyclohexa-1,4-dienyl]-2-oxo-2H-chromen-4-olate In methanol; dichloromethane at 20℃; for 2.5h;	100%
With μ-Oxo-I,I'-bis(trifluoroacetato-O)-I,I'-diphenyldiiodine(III) In water; acetonitrile at 0℃; for 2h;	100%

chloro-trimethyl-silane (75-77-4) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 1,1,1,3,3,3-hexamethyl-disilazane (999-97-3) → 1,4-bis(trimethylsiloxy)-2,5-di-tert-butylbenzene (18724-29-3)

Conditions	Yield
In acetonitrile	97%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 2,5-di-t-butyl-1,4-benzoquinone

Conditions	Yield
With [bis(acetoxy)iodo]benzene In methanol at 20℃; for 2h; Oxidation;	96%

1,3-propanesultone (1120-71-4) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → sodium 3-(2,5-di-tert-butyl-4-hydroxy-phenoxy)propane-1-sulfonate

Conditions	Yield
With sodium hydride In tetrahydrofuran at 20℃;	95%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + methyl iodide (74-88-4) → 1,4-di-tert-butyl-2,5-dimethoxybenzene (7323-63-9)

Conditions	Yield
Stage #1: 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol With sodium hydride In N,N-dimethyl-formamide; mineral oil at 20℃; for 0.25h; Inert atmosphere; Stage #2: methyl iodide In N,N-dimethyl-formamide; mineral oil at 40℃; for 2h;	94%
With sodium hydride In N,N-dimethyl-formamide at 40℃; for 2h;

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + t-butyldimethylsiyl triflate (69739-34-0) → 1,4-bis(tert-butyldimethylsiloxy)-2,5-di-(tert-butyl)benzene (73759-45-2)

Conditions	Yield
With triethylamine In chloroform at 25℃;	88%
With triethylamine In chloroform	83%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 3-nitrobenzene-1,2-dicarbonitrile (51762-67-5) → 1,4-bis-(2,3-dicyanophenoxy)-2,5-di-tert-butyl benzene (135848-92-9)

Conditions	Yield
With potassium carbonate In dimethyl sulfoxide at 20℃; for 24h;	87%
With potassium carbonate In water; dimethyl sulfoxide

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + tert-butyldimethylsilyl chloride (18162-48-6) → 1,4-bis(tert-butyldimethylsiloxy)-2,5-di-(tert-butyl)benzene (73759-45-2)

Conditions	Yield
With P(MeNCH2CH2)3N In acetonitrile at 60℃; for 18h;	86%
With 1,8-diazabicyclo[5.4.0]undec-7-ene In dichloromethane for 0.333333h; Ambient temperature;	84%

4-Nitrophthalonitrile (31643-49-9) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 1,4-bis-(3,4-dicyanophenoxy)-2,5-di-tert-butyl benzene (135848-91-8)

Conditions	Yield
With potassium carbonate In water; dimethyl sulfoxide	85%
With potassium carbonate In dimethyl sulfoxide at 20℃;

4-fluoro-2-methoxy-1-nitrobenzene (448-19-1) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 1,4-bis(3-methoxy-4-nitrophenoxy)2,5-di-tertbutylbenzene (1381864-10-3)

Conditions	Yield
With potassium carbonate In N,N-dimethyl-formamide at 160℃; for 18h;	85%

2-chloroethyl methyl ether (627-42-9) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 1,4-di-tert-butyl-2,5-bis(2-methoxyethoxy)benzene (1350770-63-6)

Conditions	Yield
With sodium hydride In tetrahydrofuran at 20℃;	81%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + 2-Bromoethyl methyl ether (6482-24-2) → 1,4-di-tert-butyl-2,5-bis(2-methoxyethoxy)benzene (1350770-63-6)

Conditions	Yield
With caesium carbonate In N,N-dimethyl-formamide at 58 - 70℃; for 5.5h;	79%

chloro-trimethyl-silane (75-77-4) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 1,4-bis(trimethylsiloxy)-2,5-di-tert-butylbenzene (18724-29-3)

Conditions	Yield
With 1,1,1,3,3,3-hexamethyl-disilazane In acetonitrile for 12h;	78%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 2,5-di-tert-butyl-p-benzoquinone (2460-77-7) + 2,5-di-tert-butyl-6-hydroxy-1,4-benzoquinone (23803-85-2)

Conditions	Yield
With air; silica gel	A 78% B 10%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + Trimethylacetic acid (75-98-9) → 2,5-di-t-butyl-4-trimethylacetoxyphenol (216314-03-3)

Conditions	Yield
sulfuric acid In hexane; di-isopropyl ether; ethyl acetate; acetonitrile	78%

[1,3]-dioxolan-2-one (96-49-1) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → 2-[2,5-Di-tert-butyl-4-(2-hydroxy-ethoxy)-phenoxy]-ethanol

Conditions	Yield
With sodium hydride In N,N-dimethyl-formamide at 140℃;	77%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + methanesulfonyl chloride (124-63-0) → methanesulfonic acid 2,5-di-tert-butyl-4-methanesulfonyloxyphenyl ester

Conditions	Yield
With triethylamine In dichloromethane at 0℃; for 0.25h;	77%

2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) + N,N-Dimethylthiocarbamoyl chloride (16420-13-6) → 1,4-bis(dimethylthiocarbamoyl)2,5-di-tert-butylbenzene

Conditions	Yield
With potassium carbonate In acetone for 48h; Reflux; Inert atmosphere;	70%

zirconocene dichloride (1291-32-3) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → [(ZrCl(C5H5)2)2(OC6H2(C4H9)2O)]

Conditions	Yield
With NEt3 In tetrahydrofuran byproducts: (HNEt3)Cl; (inert atmosphere); stirring (room temp., 2 h); filtration, addn. of hexane, sepn. after 12 h, recrystn. (THF/hexane); elem. anal.;	69%

trimethyl(pentamethylcyclopentadienyl)titanium(IV) (107333-47-1) + 2,5-bis(1,1-dimethylethyl)-1,4-benzenediol (88-58-4) → [(Ti(CH3)2(C5(CH3)5))2(OC6H2(C4H9)2O)] (176542-03-3)

Conditions	Yield
In tetrahydrofuran byproducts: methane; (inert atmosphere); stirring (room temp., 1 h); recrystn. (THF); elem. anal.;	66%

Upstream product

• 123-31-9 hydroquinone 
• 115-11-7 isobutene 
• 75-65-0 tert-butyl alcohol 
• 124700-28-3 2,5-Di-tert-butyl-4-hydroxy-phenoxyl 
• 110-87-2 3,4-dihydro-2H-pyran 
• 2460-77-7 2,5-di-tert-butyl-p-benzoquinone 
• 96455-63-9 {Fe₄S₄(S-2,4,6-(i-Pr)3C₆H₂)4}^(3-) 
• 1634-04-4 tert-butyl methyl ether 
• 64-17-5 ethanol 
• 507-20-0 tertiary butyl chloride 
• 507-19-7 t-butyl bromide 
• 3200-73-5 trans-2-butenyltrimethylstannane 
• 24850-33-7 allyltributylstanane 
• 100-99-2 triisobutylaluminum 

Downstream Products

• 2460-77-7 2,5-di-tert-butyl-p-benzoquinone 
• 124700-28-3 2,5-Di-tert-butyl-4-hydroxy-phenoxyl 
• 900-02-7 1,4-diacetoxy-2,5-di-tert-butyl-benzene 
• 7323-63-9 1,4-di-tert-butyl-2,5-dimethoxybenzene 
• 17208-03-6 2-(β,β-Dimethyl-β-methoxylethyl)-5-tert.-butyl-hydrochinon 
• 17208-05-8 2,5-Bis-(2-methoxy-2-methyl-propyl)-benzene-1,4-diol 
• 18724-29-3 1,4-bis(trimethylsiloxy)-2,5-di-tert-butylbenzene 
• 73759-44-1 1,4-bis(triethylsiloxy)-2,5-di-tert-butylbenzene 
• 73759-45-2 1,4-bis(tert-butyldimethylsiloxy)-2,5-di-(tert-butyl)benzene 
• 85629-71-6 5-[2,5-Di-tert-butyl-4-(4-methoxycarbonyl-4-methyl-pentyloxy)-phenoxy]-2,2-dimethyl-pentanoic acid methyl ester 
• 130442-22-7 4-dodecyloxy-2,5-di-t-butylphenol 
• 1969-47-7 1,4-Dicyanato-2,5-di-tert.-butyl-benzol 
• 23803-85-2 2,5-di-tert-butyl-6-hydroxy-1,4-benzoquinone 
• 103858-52-2 4-bromo-1H-Indole-2-carboxylic acid ethyl ester 

Relevant articles and documents

Preparation method of 2, 5-di-tert-butyl-p-dimethoxybenzene

The invention discloses a preparation method of 2, 5-di-tert-butyl-p-dimethoxybenzene, which comprises the following steps: (1) reacting tert-butyl alcohol with hydroquinone in a first solvent under the action of a first catalyst, cooling and crystallizing after the reaction is finished, filtering, washing and drying to obtain 2,5-di-tert-butyl hydroquinone; and (2) reacting the 2, 5-di-tert-butyl hydroquinone obtained in the step (1) with methyl iodide in a second solvent under the action of a second catalyst, cooling to room temperature after the reaction is finished, adding brine and an organic solvent into the reaction liquid for extraction, washing the obtained organic layer, and performing vacuum drying to obtain the 2, 5-di-tert-butyl-p-dimethoxybenzene product. The method has the advantages of simple process, mild reaction conditions, environmental protection, low cost and high yield.

1-Methyl-1,4-cyclohexadiene as a Traceless Reducing Agent for the Synthesis of Catechols and Hydroquinones

Pro-aromatic and volatile 1-methyl-1,4-cyclohexadiene (MeCHD) was used for the first time as a valid H-atom source in an innovative method to reduce ortho or para quinones to obtain the corresponding catechols and hydroquinones in good to excellent yields. Notably, the excess of MeCHD and the toluene formed as the oxidation product can be easily removed by evaporation. In some cases, trifluoroacetic acid as a catalyst was added to obtain the desired products. The reaction proceeds in air and under mild conditions, without metal catalysts and sulfur derivatives, resulting in an excellent and competitive method to reduce quinones. The mechanism is attributed to a radical reaction triggered by a hydrogen atom transfer from MeCHD to quinones, or, in the presence of trifluoroacetic acid, to a hydride transfer process.

Diels-Alder trapping of in situ generated dienes from 3,4-dihydro-2H-pyran with p-quinone catalysed by p-toluenesulfonic acid

This comprehensive study portrays that p-toluenesulfonic acid is a more efficient catalyst for the reaction between p-quinones and 3,4-dihydro-2H-pyran, than the Lewis acids. The products were accomplished by the Diels-Alder cycloaddition reaction and their mechanistic pathways have been formulated. The impact of C2 and C2,5 substituents of the p-quinones on the cycloaddition reaction has been explored. Remarkably, it is the first report to explore this kind of in situ generated diene for the Diels-Alder cycloaddition reaction.