No abstract

5) Typically. to 0.65 g 01 hydroquinone 2a in 3.8 mL of 3 1 toluene-methanol is added 1.7 g of Sephsdex LH-20 (Pharmacie Fine ChemicBIsl. The gel sets immediately. A soilnion 01 0.25 g 01 quinone l a in 4 mL 01 the same Solvenl is poured on top 01 me gel and the Container allowed to stand at room temperature. A black precipitate farms at the interlace and, as the SOIutions slowly dilluse together. a deep Coloration develops. Small well-formed crystals gmw within the bo@ of tha gel aher -24 h. The crystals. aher they have anained the desired size. are removed t o m the gel by washing With

No abstract

20) In many epoxide cyclization experiments, significant amounts of acyclic ketone resulting from simple rearrangement are formed, despite the greatly enhanced reaction rate due to the neighboring ir bond.6 As an explanation for this and other cyclization results, there may be generated with participation some type of partially cyclized intermediate cation common to all processes, reacting with external nucleophiles (or bases) to give acyclic and monocyclic material as well as with further double bonds to give polycyclics. As a particularly attractive feature, this hypothesis (proposed by Professor J. Brauman) accounts both for the rate acceleration in production of noncyclized material as well as the lack of extra acceleration in the rate of polycycle formation.

No abstract