Tributyl borate → 3-Phenyl-2-thiophenecarboxaldehyde
Reaction equation
[CH:1]([C:3]1[S:4][CH:5]=[CH:6][C:7]=1B(O)O)=[O:2].Br[C:12]1[CH:16]=[CH:15]S[C:13]=1[CH:17]1OCCO1.[CH2:22]([Li])CCC.B(OCCCC)(OCCCC)OCCCC>BrC1C=CC=CC=1.C(=O)([O-])[O-].[Na+].[Na+].C(O)C>[C:13]1([C:7]2[CH:6]=[CH:5][S:4][C:3]=2[CH:1]=[O:2])[CH:12]=[CH:16][CH:15]=[CH:22][CH:17]=1Participants
Reactant 4
Product 1
Reagents, catalysts & solvents 2
Procedure
3-bromothiophen-2-aldehyde (2) was obtained from commercially available 2,3-dibromothiophen (1) via 3-bromothienyllithium and reaction with N,N-dimethylformamide. The aldehyde 2 was protected by reaction with ethylene glycol to give 2-(3-bromo-2-thienyl)-1,3-dioxolane (3). The latter derivative was converted into 2-formyl-3-thiopheneboronic acid (4) using halogen-metal interconversion between the substrate (3) and butyllithium at −70° C., followed by treatment with tributyl borate and subsequent hydrolysis. The thienylboronic derivative 4 is a very useful intermediate, in fact it can be condensed with various bromo-aromatic compounds. Thus, palladium-catalysed condensation reaction of the derivative 4 with bromobenzene in aqueous sodium carbonate-ethanol mixture as solvent gave 3-phenyl-thiophen-2-carboxaldehyde (5). Oxidation of 5 with Jones' reagent yielded 3-phenyl-thiophen-2-carboxylic acid (6). Chlorination of 6 with thionyl chloride followed by reaction with sodium azide yielded the acyl azide intermediate which on thermolysis in boiling o-dichlorobenzene gave the derivative thieno[2,3-c]isoquinolin-5(4H)-one (7).
Workup
- customat −70° C.
Sources & evidence
- ORD record
- ord-8610ce156a624f0f8dae455da6bdc88a
- Source dataset
- uspto-grants-2010_11
- Patent number
- US07825129B2
Reaction notes
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