DABAL-Me₃: A Versatile Methylating Agent

Introduction

DABAL-Me₃ is a very suitable, easy to use reagent to ­methylate a variety of functional groups like aldehydes, imines, enones, amides, etc. Although trimethyl aluminium has been traditionally used as a methylating agent, its pyrophoric nature stands as a major obstacle in its sustainability. Several other Me₃Al˙NR₃ species such as Me₃Al˙pyridine, Me₃Al˙TMEDA (tetramethyletyhylenediamine) are also reported, but they are too reactive to be used under normal laboratory conditions. DABAL-Me₃, which is actually a 2:1 complex of Me₃Al and DABCO, is free from these shortcomings as it can be manipulated without the need for an inert atmosphere. [¹] [²]

DABAL-Me₃ can be prepared by adding neat AlMe₃ to freshly sublimed DABCO in toluene at 0 ˚C. The white precipitate is separated from toluene and washed several times with diethyl ether. [³] The versatility of the reagent can be easily assessed by its capability to methylate a wide variety of substrates.

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