3-Ethyl-5,5-dimethyl-4,5,6,7-tetrahydro-benzo[c]thiophene-1-carboxylic acid → 1-(3-Ethyl-5,5-dimethyl-4,5,6,7-tetrahydro-benzo[c]thiophen-1-yl)-ethanone
Reaction equation
[CH2:1]([C:3]1[S:7][C:6]([C:8]([OH:10])=O)=[C:5]2[CH2:11][CH2:12][C:13]([CH3:16])([CH3:15])[CH2:14][C:4]=12)[CH3:2].[CH3:17][Li]>CCOCC>[CH2:1]([C:3]1[S:7][C:6]([C:8](=[O:10])[CH3:17])=[C:5]2[CH2:11][CH2:12][C:13]([CH3:16])([CH3:15])[CH2:14][C:4]=12)[CH3:2]Participants
Procedure
To a solution of 3-ethyl-5,5-dimethyl-4,5,6,7-tetrahydro-benzo[c]thiophene-1-carboxylic acid (2.10 g, 8.81 mmol) in Et2O (100 mL), a solution of methyllithium (11 mL, 1.6 M solution in Et2O) is added at rt. The pale yellow solution is stirred at rt for 15 min before another portion of methyllithium (2 mL) is added. Stirring is continued for 15 min, a further portion of methyllithium (1 mL) is added, and the mixture is again stirred for 15 min at rt. The reaction is quenched with water. The organic layer is separated, washed once more with water, dried over MgSO4 and evaporated. The crude product is purified by CC on silica gel eluting with heptane:EA 7:3 to give 1-(3-ethyl-5,5-dimethyl-4,5,6,7-tetrahydro-benzo[c]thiophen-1-yl)-ethanone (1.65 g) as a pale yellow solid; LC-MS: tR=1.00 min, [M+1]=237.15; 1H NMR (CDCl3): δ 3.03 (t, J=7.0 Hz, 2H), 2.73 (q, J=7.6 Hz, 2H), 2.47 (s, 3H), 2.31 (s, 2H), 1.55 (t, J=7.0 Hz, 2H), 1.28 (t, J=7.6 Hz, 3H), 0.97 (s, 6H).
Workup
- additionis added
- stirringthe mixture is again stirred for 15 min at rt
- customThe reaction is quenched with water
- customThe organic layer is separated
- washwashed once more with water
- dry with materialdried over MgSO4
- customevaporated
- customThe crude product is purified by CC on silica gel eluting with heptane:EA 7:3
Sources & evidence
- ORD record
- ord-968ba581c42640959b66c738363fbf10
- Source dataset
- uspto-grants-2014_04
- Patent number
- US08697732B2
Reaction notes
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