Noncatalytic Annulation of 4-Hydroxy-4-methylpent-2-ynenitrile to 3,3-Dimethyl-2-phenyl-3H-pyrrole. Stereoselective Synthesis of (Z)-2-(2,2,7,7-Tetramethyl-7a-phenyl-7,7a-dihydropyrrolo- [2,1-b]oxazol-3(2H)-ylidene)acetonitrile