Synthesis of Bio-Based PTMG

To achieve more efficient direct methylation of lactic acid, the hindered lithium amide supported by cross-linked polystyrene was prepared from commercially available Merrifield resin. Obtained pol5mier-supported hindered lithium amide/methyl iodide system was found to be an efficient condition for the a-methylation reaction of lactic acid derivatives, giving excellent 3delds of a-methylated products (98%) under room temperature for a very short reaction time [101]. 

The cyclic dimerization of HIBA proceeded smoothly in the presence of the dehydration catalyst methane sulfonic acid to isolate the cyclic dimer TMG in a 67% 5deld. Another simple and convenient route for the s5mthesis of TMG from lactic acid has been reported [102]. This method involves three steps (1) one-step protection of lactic acid hy cyclic acetalization employing acetone (2) cc-methylation of the obtained 2,2,5-trimethyl-l,3-dioxolan-4-one and [3] one-pot s5mthesis of TMG including the hydrolysis of 2,2,5,5-tetramethyl-l,3-dioxolan-4-one, resulting in moderate 5deld [49-51%] of TMG. 

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