[80-73-9] · C5H10N2O · 1,3-Dimethyl-2-imidazolidinone · (MW 114.17)
Alternate Name: DMI.
Physical Data: bp 221-223 °C; d 1.044 g cm-3.
Solubility: sol water, DMF, and THF.
Form Supplied in: clear, colorless liquid; commercially available.
Analysis of Reagent Purity: bp, NMR.
Purification: distillation over calcium hydride under reduced pressure.
Handling, Storage, and Precautions: for best results, this solvent should be stored under an inert atmosphere over 4Å molecular sieves. Handle in a fume hood.
DMI is the solvent of choice for palladium-catalyzed carbonyl allylation of allylic alcohols (eq 1).3 Allylation of ketones requires higher temperatures (eq 2). Preferential reaction of an aldehyde in the presence of a ketone can be achieved (eq 3). Allylic iodides can also be reacted with aldehydes and ketones in the presence of Tin(II) Fluoride4 to form homoallylic alcohols in good yield without the use of Lewis acids as additives (eq 4).
Palladium-catalyzed allylation of aldehydes and ketones with ethyl a-(hydroxymethyl)acrylate in the presence of Tin(II) Chloride in DMI/water provides a-methylene-g-butyrolactones (eq 5).5 Syn selectivity has been achieved when the reactions are run using a substituted hydroxymethylacrylate.
DMI is the solvent of choice for the preparation of TMSNa, Trimethylsilylpotassium, and Trimethylsilyllithium (eq 6).6 Other polar aprotic solvents such as DMF, DMSO, and tetramethylurea (TMU) are not suitable due to their reactivity toward strong base and alkali metals. Reactions of these species are also run in DMI (eqs 7 and 8).2
DMI can be used as an alternative for HMPA7 in dehydration and dehydrohalogenation reactions using Methyltriphenoxyphosphonium Iodide (MTPI) (eq 9).
Preparation of m-phenoxybenzyl alcohol by condensation of m-hydroxybenzyl alcohol with chlorobenzene works best in DMI (eq 10).8 Lower yields result when the reaction is run using DMSO or DMF.
Reactions of propargyl iodides with aldehydes in the presence of SnCl2 in DMI/DMF yield a mixture of a-hydroxylallenes and b-hydroxyalkynes9 (eq 11).
High syn selectivity is achieved in Wittig-Horner reactions between aldehydes and diphenylphosphonates when run in THF/DMI at low temperature.10 Subsequent stereospecific elimination yields cis-alkenes (eq 12).
Ellen M. Leahy
Affymax Research Institute, Palo Alto, CA, USA