The Matteson Epoxidation allows the preparation of oxiranes from carbonyl compounds and (bromomethyl)lithium. The Matteson Homologation allows the conversion of boronic esters by the insertion of methylene into the C–B bond.
General features:
1. The (bromomethyl)lithium species is generated in situ by the addition of butyllithium to dibromomethane in the presence of a suitable substrate at –78 ºC.
2. (Chloromethyl)lithium, generated by the addition of n-BuLi to DCM, is sometimes employed instead. However, (bromomethyl)lithium offers significant advantages over the previous one in some applications.
3. Aldehydes or ketones yield oxiranes, while boronic esters without functional substituents undergo methylene insertion into the carbon-boron bond.
4. Boronate complexes do not rearrange at −78°C. This prevents multiple insertions of (dihalomethyl)lithium as any excess reagent decomposes before the homologated boronic ester has been formed.
5. The electrophilic nature of boron results in an efficient ate-complex, inhibiting side reactions such as β-elimination.
Reaction mechanism:
1. Addition of n-butyllithium, n-BuLi, to equimolar amounts of dibromomethane generates the lithium carbenoid that inserts into the carbonyl compound. Then, the intermediate alkoxide attacks the electrophilic halomethyl group generating the three-membered cycle.
2. Addition of the bromomethyllithium at the boron center followed by a 1,2-rearrangement of the ate complex.
References:
NROChemistry: [ Ссылка ]
Seminal publication:
Michnick, T. J., Matteson, D. S. Synlett, 1991, 631.
