1.1: 73 percent / p-toluenesylfonic acid monohydrate / CH2Cl2 / 52 h / 20 °C 2.1: n-BuLi, lithium naphthalenide / tetrahydrofuran; hexane / 0.5 h / -78 °C 2.2: 86.6 percent / tetrahydrofuran; hexane / -78 - 0 °C View Scheme