Tert-BuOH

The structure of anhydrovobasindiol (35, C20H24N20, MP 208°C, [a]D —243°) was based almost entirely on chemical evidence. Hydrogenation of 35 gave a dihydro derivative (C20H26N20, MP 191-193°C), which formed a meth-iodide on reaction with Mel. Hofmann elimination with tert-BuOK in tert-BuOH... 

Quininone, the most readily available member of the series, was used for the autoxidation studies. The Doering autoxidation procedure,4 that employs only tert-BuOH, was modified to include a THF tert-BuOH (4 1) mixture as the solvent. Likewise, the pressurized Parr bottle setup as described4 was replaced with a simple subsurface gas addition the solvent was presaturated with O2 gas, (compressed air could also be used as the O2 source) followed by t-BuOK addition and continued O2 gas purge. The autoxidations could likewise be conducted in the presence of ethanol or methanol, thereby producing the corresponding ethyl or methyl esters. Formation of these esters could occur via the reactive intermediate bicyclic lactam.4... 

Substrate, M KOC(CHs)s, M tert- BuOH Pyridine(80% )-tert-BuOH(20% ) DMSO(80%y tert-BuOH(20%)... 

LDH-OSO4 (lOmg. 0.0134mmol) was added to around-bottomed flask containing aqueous buffer solution (12.5 mL, pH 10.4) and tert-BuOH (5mL) and stirred at 1 bar O2, 55 °C in an oil bath. Then methyl sulfide (0.124g, 1 mmol) was added in one portion and the reaction mixture was stirred vigorously. The reaction was completed in 8 h as monitored by TLC. 

Similar calculations for tert-BuO /teri-BuOO" using bond energies in Table VII and again assuming similar rate constants for the identity reactions for tert-BuO /tert-BuOH and tert-BuOO /tert-BuOOH yields feniuo/ iiuoo 106, close to the experimentally observed value. A large source of error in this and other calculated ratios comes from the uncertainty in the bde s, which sometimes differ widely from source to source (160). 

Since that time several other metal-solvent systems have been found useful, effective, and selective in the partial hydrogenation of alkynes. The mechanism of the transformation depends on the nature of the solvent and the substrate. Detailed studies were carried out with the Na-HMPA-tert-BuOH system,197 resulting in the suggestion of the mechanism depicted in Scheme 11.10. 

Me02 + tert- Bu02 — CH20 + tert- BuOH + 02... 

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