Reductive openings of benzylidene acetals. Kinetic studies of borane and alane activation by Lewis acids.

• The reaction kinetics for a number of reductive openings of methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-d-glucopyranoside have been investigated. Openings to give free HO-6 (using BH(3).THF-AlCl(3)-THF or LiAlH(4)-AlCl(3)-Et(2)O) follow first order kinetics, while reactions yielding free HO-4 (using BH(3).NMe(3)-AlCl(3)-THF or BH(3).NMe(3)-BF(3).OEt(2)-THF) follow higher order kinetics. The addition of water to the BH(3).NMe(3)-AlCl(3)-THF results in faster reactions. The BH(3).SMe(2)-AlCl(3)-THF system constitutes a borderline case, yielding both free HO-6 (by a first order reaction) and free HO-4 (by a higher order reaction). These results correlate well with the concept of regioselectivity by activation of borane complexes.

Subject headings

NATURVETENSKAP  -- Kemi -- Organisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Organic Chemistry (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Immunologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Immunology in the medical area (hsv//eng)

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art (subject category)

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