How is N,N,N-Trimethylmethanaminium tris(acetato-kappaO)(hydrido)borate(1-) (CAS: 109704-53-2) typically synthesized?

N,N,N-Trimethylmethanaminium tris(acetato-kappaO)(hydrido)borate(1-) is commonly synthesized through a multi-step process involving the reaction of trimethylmethanamine with acetic anhydride and boron trifluoride. The reaction typically yields a mixture which can be purified by recrystallization from acetone. The process requires careful control of temperature and reagent ratios to achieve desired product purity and selectivity.