Cob (I)alamin als Katalysator 4. Mitteilung. Reduktion von α,β‐ungesättigten Nitrilen

Abstract

Cob(1)alamin as Catalyst 4. Communication. Reduction of a$-Unsaturated Nitriles SummaryUsing catalytic amounts of cob (1)alamin and an excess of metallic zinc as source of electrons 1-naphthonitril (5) has been reduced to (1-naphl.hyl)methylamin (6) and in small amounts to (1-naphthy1)methanol (7) and (1,2,3,4-tetrahydro-lnaphthy1)methanol (8) ( 5 % h, CH,COOH/H,O; s. Scheme 3). Starting from cyclododecylideneacetonitrile (15) similar conditions (68 h, CH3CO~OH/H20) produced the amines 16-19 as well as the nitrogen free saturated aldehyde 20, the corresponding allylic alcohol 21 and the saturated derivative 22 (s. Scheme 6). It is deduced that the first attack of cob(1)alamin on an a,B-unsaturated nitrile might occur on both the nitrile dipole as well as on the carbon atom in P-position. Cob(1)alamin in aqueous acetic acid saturates the isolated double bonds in allylic alcohols and amines. In a slow reaction the two different aromatic rings of (1 -naphthyl)methanol (7) have been reduced giving the corresponding tetrahydronaplithalene derivatives 8 and 12, and in one case the production of the octahydroderivative 14 has been observed in a low yield (s. Scheme 5).In einer fruheren Untersuchung dieser Reihe wurde gezeigt, dass mit katalytischen Mengen Cob (1)alamin (vgl. Schema I) a , p-ungesattigte Nitrile reduziert werden konnten [ 11. Dabei fie1 auf, dass bei (2)-I-Cyclododecencarbonitril (1; vgl. Schema 2) zuerst in einer schnellen vorgelagerten Reduktion') die Doppelbindung abgesattigt wurde und anschliessend in einer langsameren Umsetzung*) das gesattigte Nitril3, uber ein entsprechendes Imin3), unter den wasserig sauren Bedingungen zum gesattigten Aldehyd 4 reduziert wurde. Dabei stellte sich die Frage, ob generell durch Cob (1)alamin u , P-ungesattigte Nitrile zuerst in P-Stellung und erst anschliessend am Nitril-dipol angegriffen werden. 3)Vgl. [2].

Asymmetric catalysis in fragrance chemistry: a new synthetic approach to enantiopure Phenoxanol®, Citralis® and Citralis Nitrile®

“…15 Olefin 6 was isolated as a pale yellow oil (90% yield). The GC-MS and 1 H NMR data 26 were identical to those reported in the literature. 13 anhydrous CH 2 Cl 2 contained in a small Schlenk flask were added 100 mg (0.57 mmol) of (Z)-3-methyl-5-phenyl-pent-2-en-1-ol under an inert atmosphere.…”

Electrofugal Fragmentation of Alkylcobalamin Derivatives Using Cob(I)Alamin and Heptamethyl Cob (I)yrinate as Catalysts

“…of activated37) metallic zinc were added to the red solution. The suspension was stirred at r.t. under Ar until3*) a dark green colour revealed the presence of cob (1) 37) For the procedure used to activate zinc, see [9]. 38) For the development of the green color, a period of 5-10 min was usually required.…”

“…Reduction of 3 to 10-undecenyl acetate (4, undecyl acetate (5) and by-products 6-12 using cob (I) alamin (l(1)) as catalyst. Following the procedure described earlier [9], 600 mg (0.1 mol-equiv.) of cyanocob(I1I)alamin (1) was transformed into the catalyst.…”

“…The procedure followed during a usual or normal extraction is described in [14]. Except in the kinetic experiments, the catalysts were prepared following the prescriptions published in [9]. The preparation of the catalysts used in the kinetic experiments is given below.…”

“…During studies of the saturation of trisubstituted double bonds leading to optically active products, very little influence of light was detected on the enantiomeric excess of the saturation products [9]. The homolytic fission of the Co,C-bond is therefore not a product-forming reaction under the conditions applied.…”