[H-].[Na+].[N+:3]([C:6]1[CH:11]=[CH:10][C:9]([CH2:12][C:13]([OH:15])=[O:14])=[CH:8][CH:7]=1)([O-:5])=[O:4].OS(O)(=O)=O.Br[CH2:22][CH2:23][CH2:24]Br.[H-].CN([CH:30]=[O:31])C>O.CO>[N+:3]([C:6]1[CH:7]=[CH:8][C:9]([CH2:12][C:13]([O:15][CH3:22])=[O:14])=[CH:10][CH:11]=1)([O-:5])=[O:4].[N+:3]([C:6]1[CH:7]=[CH:8][C:9]([C:12]2([C:13]([O:31][CH3:30])=[O:15])[CH2:24][CH2:23][CH2:22]2)=[CH:10][CH:11]=1)([O-:5])=[O:4]NaH (80% dispersion in mineral oil, 0.26 mol) was suspended in DMF under nitrogen atmosphere. Methyl 4-nitrophenylacetate (0.13 mol), that was prepared by refluxing 4-nitrophenylacetic acid (0.2 mol) with MeOH (100 mL) and conc. H2SO4 (1 mL) for 24 h, dissolved in DMF was added dropwise followed by 1,3-dibromopropane (0.13 mol) in DMF. stirring was continued at room temperature for 1.5 h. Excess hydride was then decomposed by the cautious addion of H2O. More H2O was added and extracted with toluene. The organic layer was washed with H2O, dried (MgSO4) and concentrated to give methyl 1-(4-nitrophenyl)-cyclobutanecarboxylate that was stirred with 0.5 M NaOH (128 mL) in THF overnight. THF was evaporated, the residue was dissolved in H2O and extracted with EtOAc. The aqueous layer was acidified and extracted with EtOAc. The organic layer was dried (MgSO4) and concentrated to give the desired product that was washed with EtOH/H2O. The yield was 0.7 g (12%); 1H NMR (CDCl3) δ 1.90 (m, 1H), 2.05-2.20 (m, 1H), 2.50-2.60 (m, 2H), 2.90 (m, 2H), 7.52 (d, 2H), 8.2 (d, 2H).
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