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Reaction of selected carbohydrate aldehydes with benzylmagnesium halides: benzyl versus o-tolyl rearrangement

M. Bella ; B. Steiner ; Vratislav Langer (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; M. Koos
Beilstein Journal of Organic Chemistry (1860-5397). Vol. 10 (2014), p. 1942-1950.
[Artikel, refereegranskad vetenskaplig]

The Grignard reaction of 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside and benzylmagnesium chloride (or bromide) afforded a non-separable mixture of diastereomeric benzyl carbinols and diastereomeric o-tolyl carbinols. The latter resulted from an unexpected benzyl to o-tolyl rearrangement. The proportion of benzyl versus o-tolyl derivatives depended on the reaction conditions. Benzylmagnesium chloride afforded predominantly o-tolyl carbinols while the application of benzylmagnesium bromide led preferably to the o-tolyl carbinols only when used in excess or at higher temperatures. The structures of the benzyl and o-tolyl derivatives were confirmed unambiguously by NMR spectral data and X-ray crystallographic analysis of their 5-ketone analogues obtained by oxidation of the corresponding mixture of diastereomeric carbinols. A possible mechanism for the Grignard reaction leading to the benzyl -> o-tolyl rearrangement is also proposed.

Nyckelord: aldehyde, benzyl versus o-tolyl, carbohydrate, Grignard reaction, rearrangement, X-ray crystallography



Denna post skapades 2014-09-15. Senast ändrad 2014-09-25.
CPL Pubid: 202755

 

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Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Kemi

Chalmers infrastruktur