how to use di-tert-butyl dicarbonate (diBOc) as a solvent?
Di-tert-butyl dicarbonate melts around room temperature (m.p.=23°C).  It does not decompose at this or even slightly higher temperatures.  For example, it is typically purified by distillation under reduced pressure at temperatures up to around 65°C.  At higher temperatures it will decompose to isobutene, t-butyl alcohol and carbon dioxide.



In any case it is OK to melt di-tert-butyl dicarbonate and use it between room temperature and up to around 40-60°C.  Just make sure that when you open the bottle and use it that you do so in a dry environment as water will decompose di-tert-butyl dicarbonate.