Diels-Alder Reaction

Mechanism of the Diels-Alder Reaction

Original publication	Liebigs Ann.. 1928, 460, 98. Chem. Rev.. 1961, 61, 537. Chem. Rev.. 1962, 62, 405. Chem. Rev.. 1986, 86, 781. Chem. Soc. Rev.. 1987, 16, 187. Chem. Rev.. 1992, 92, 1007. Org. React.. 1984, 32, 1. Org. React.. 2005, 65, 141. Chem. Rev.. 2008, 108, 2051. Tetrahedron. 2002, 58, 2381.
Reviews	Angew. Chem. Int. Ed.. 2002, 41, 1668. Angew. Chem. Int. Ed.. 2002, 41, 1650. Chem. Rev.. 1980, 80, 63.

Sample reactions

2-Chloroacrylonitrile, Cu(BF4)2

0 °C

Et2NH

Et2O

-20 °C, , 40% (3 steps)

THF

-78 °C to RT, , 23%

PhH

Reflux, 60 min, 100%

"Mixture of isomers."

PhH

Reflux, 10 h, 8%

""[This method was not] investigated extensively with a view to determining optimum conditions.""

Methyl acrylate, AlCl3

CH2Cl2

-78 °C, 7 h, 98%

DBAD

CH2Cl2

RT, 36 h

1,3-Butadiene

PhH

100 °C, 96 h, 86%

NaOAc, PdCl2

H2O, MeOH

38 °C to RT, 3 h, 46%

2-Chloroacrylonitrile

Sealed tube

PhH

130 °C, 72 h, 85%

Neopentyl glycol, PhB(OH)2

Dean-Stark

PhH

RT to Reflux, 48.5 h, 61%

O2, Tetraphenylporphyrin

hν

CH2Cl2

RT, 7 h

CH2Cl2

RT, 20 h, 47% (2 steps)

"95 % yield based on the alkene."

Sealed tube

PhH

90 °C, 5 h, 55%

BF3.OEt2

PhMe

-78 °C, 85 min, 59%

"The product was separated from the resulting three diastereoisomers."

SnCl4

PhH

RT, , 73%

"The enantiomers were resolved with (+)- and (-)-phenylethylamine."

PhH

RT, 2-3 weeks, 93%

PhMe

90 °C, 24 h, 88%

CCl4

Reflux, 2 h, 100%

PhMe

Reflux, 60 min, 92%

Maleic anhydride

PhH

80 °C, 12 h, 98%

SnCl4

MeCN

RT, 24 h

i-Pr2NLi

THF

-78 to 0 °C, 3 h, 88%

µW

PhMe

2.5 h, 97%

DEAD, I2

THF

4.4%

Pyrrolidine

MeOH

60 °C, 4.5 h, 78%

98-105 °C, 120 h, 61%

PhMe

300 °C, 8 h, 23%

"The yield was 76 % brsm."

PhMe

250 °C, 22 h, 44%

"Also isolate was the C14-epimer (24 % yield)."

1,3-Butadiene

Dioxane

85-87 °C, 72 h, 66%

1,3-Butadiene

PhMe

"No yield given."

BHT

PhMe

120 °C, 24 h, 92%

RT, 30 h, 97%

Acrolein

H2O, MeCN

RT, 14 h

Et3N

Decalin

235-240 °C, 24 h, 55%

"The yield was 70 % brsm. Also isolated was the C2-epimer (14 % yield)."

MgI2

µW

PhMe

150 °C, 3 h, 95%

Sealed tube

PhH

185-200 °C, 4 h, 99%

PhNEt2

Reflux, 60 min, 100%

KOt-Bu

Sealed tube

THF

80 °C, 3.5 h, 64%

NH3

CH2Cl2

0 °C to RT, 60 min, 47% (2 steps)

H2O

DMSO

155 °C, 3.5 h, 86%

80-85 °C, 24 h, 36%

Sealed tube

Mesitylene

160 °C, 72 h, 85%

n-Pr4N+ IO4-

CHCl3

0 °C, , 57%

"Also isolated was the C-4a epimer (31 %)"

ZnCl2

THF

-80 °C to RT, 16 h, 51%

NaOH

MeOH

Reflux, 2 h, 60% (2 steps)

PhH

Reflux, 2 h, 90%

Et2O

0 °C, 60 min, 100%

i-Pr2NEt, Hydroquinone

PhMe

85 °C, 4 h, 21% (2 steps)

"The yield was 27 % brsm."

Me2AlCl

CH2Cl2

-78 °C, 15 min, 79%

PhMe

120 °C, 24 h, 91%

Mesitylene

Reflux, 24 h, 70%

Ac2O

125 °C, 30 h, 74%

PhH

RT, 3 h

110 °C, 3 d, 87%

Reflux, 48 h, 82%

PhMe

100 °C, , 30% (2 steps)

Decane

Reflux, 20 h, 71% (2 steps)

1,2,4-Trichlorobenzene

200 °C, 5 h, 67%

SiO2

THF

-78 °C to RT, 8 h

i-Pr2NEt, LiCl

MeCN

RT, 12 h, 55%

"Also produced were 2 other diastereomers (20% yield)"

Et2AlCl, 1,3-Butadiene

CH2Cl2

-78 to -7 °C, 16 h, 56%