Roche patent

According to a Hoffmann-la-Roche patent procedure, acetylene is added to acetone in the presence of a base. Reduction with a Lindlar catalyst gives 2-methylbut-3-en-2-ol. Treatment of this with diketene and sodium methoxide renders an isolable acetoacetate ester, which undergoes at 160 °C a Carroll reaction [58] (a Claisen rearrangement with loss of carbon dioxide) to yield the desired intermediate product. 

The current paradigm for B syntheses came from the first report in 1957 of a synthesis of pyridines by cycloaddition reactions of oxazoles (36) (Fig. 5). This was adapted for production of pyridoxine shordy thereafter. Intensive research by Ajinomoto, BASF, Daiichi, Merck, Roche, Takeda, and other companies has resulted in numerous pubHcations and patents describing variations. These routes are convergent, shorter, and of reasonably high throughput. 

---