Enantioenriched ω-bromocyanohydrin derivatives. Improved selectivity by combination of two chiral catalysts

• Highly enantioenriched (R)-4-bromo-1-cyanobutyl acetate and (R)-5-bromo-1-cyanopentyl acetate were prepared by acetylcyanation of 4-bromobutanal and 5-bromopentanal, respectively, catalyzed by (S,S)-[(4,6-bis(t-butyl)salen)Ti(ÎŒ-O)] 2 and triethylamine followed by enzymatic hydrolysis of the minor enantiomer. A cyclic procedure employing the same two chiral catalysts provided inferior results due to a slowly reached steady state and, in reactions with the former substrate, to ring-closure of the free cyanohydrin formed as an intermediate in the reaction. Hydrolysis of the acylated cyanohydrins followed by AgClO 4-promoted cyclization provided (R)-2-cyanotetrahydrofuran and (R)-2-cyanotetrahydropyran in essentially enantiopure form.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

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

Keyword

2-Cyanotetrahydrofuran

2-Cyanotetrahydropyran

Acetylcyanation

Enzymatic hydrolysis

Kinetic resolution

Publication and Content Type

ref (subject category)

art (subject category)