Pyrrolidine → 2-(Propan-2-yl)-5-(propan-2-ylidene)cyclopenta-1,3-diene

HRID 726156Notes

Reaction equation

HRID 726156 reaction equation
[CH:1]([C:4]1[CH2:8][CH:7]=[CH:6][CH:5]=1)([CH3:3])[CH3:2].N1C[CH2:12][CH2:11][CH2:10]1>CC(C)=O>[CH:1]([C:4]1[CH:8]=[CH:7][C:6](=[C:11]([CH3:12])[CH3:10])[CH:5]=1)([CH3:3])[CH3:2]

Participants

4

Reactant 2

HCID 31268PyrrolidineHCID 528163HCID 528163, compound

Product 1

HCID 143632832-(Propan-2-yl)-5-(propan-2-ylidene)cyclopenta-1,3-diene

Reagents, catalysts & solvents 1

HCID 180AcetoneSolvent

Procedure

Therefore, 1,3-diisopropylcyclopentadiene was selected as the starting point for the synthesis. Unfortunately, the reported syntheses of 1,3-diisopropylcyclopentadiene gave low yields since the final step was always separation of the 1,3 product from the 1,2 product. A more selective method was found by extension of work by Nile in which he prepared a number of 1,3 disubstituted cyclopentadienes using a fulvene route. Using this method, reaction of isopropylcyclopentadiene with acetone catalyzed by pyrrolidine gave the 3-isopropyl-6,6-dimethylfulvene. Subsequent reduction of the fulvene with LAH and hydrolysis provided 1,3-diisopropylcyclopentadiene, "iPr2Cp." ##STR10##

Workup

  1. customyields since the final step
  2. customseparation of the 1,3 product from the 1,2 product
  3. customprepared a number of 1,3 disubstituted cyclopentadienes using a fulvene route

Sources & evidence

ORD record
ord-24ff7d2e978646ffacc461b028c45735
Source dataset
uspto-grants-1998_01
Patent number
US05708101

Reaction notes

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