5-Bromo-2-methyl-2-pentene → 3-(4-Methylpent-3-en-1-yl)cyclopent-2-en-1-one

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Reaction Steps

Magnesium turnings 2.1 g (0.086 mole) were added to 50 ml diethyl ether with stirring. 1-Bromo-4-methyl-3-pentene 10 g (0.061 mole) was added dropwise over 30 minutes. The reaction was allowed to warm from 25° C. to 40° C. during the addition and aged for 30 minutes. A solution of 3-Methoxy-2-cyclopenten-1-one, 10 g (0.089 mole) in diethyl ether was added at 25° C. The resulting mixture was aged 30 minutes then quenched with 20% aqueous acetic acid (50 ml). The organic layer was dried over sodium sulfate, filtered and distilled to give 6.6 g (65% yield) of 3-(4-methyl-3-pentenyl)-2-cyclopenten-1-one.

Provenance & Evidence