W-Benzylation

A polyacrylamide with a molecular mass of 1.87 x 105 was prepared by polymerising a 5% w/v aqueous solution of acrylamide monomer in the presence of 0.15% w/w benzyl alcohol and 0.025% w/w potassium persulphate for 45 minutes at 80 °C. This product was effective in preventing the bleeding of direct dyes and hydrolysed reactive dyes from dyed cotton, which was simply dipped in a 1% solution of the polyacrylamide and dried in air [450]. 

The highly enantioselective reductive animation of a-keto acids as a route to amino acids is possible with ligand 118 (3 R,4R)- l-W-benzyl)-3,4-bis(diphenylphosphanyl)pyrrolidine, DEGUPHOS] and [Rh(cod)2]BF4.649 (R,R)-NORPHOS (2-exo-3-endo-bis(diphenylphosphino)bicyclo[2.2.1 ]heptene) and (2. S, 3. S ) - C HIR AP H O S (bis(diphenylphosphino)butane) are also good ligands for this transformation. Arylpyruvic acids give the best results (>95% ee). 

W-benzyl-TV-hydroxylamine)phenylmethyl]-3-hydroxybutanoate (398) (637). The absolute configuration (398) was determined as (aRfiS,yR) thus, diastere-oselective addition of ketene silyl acetals (397) to nitrone proceeds as anti-a, p-anti-p, y (Scheme 2.176). 

A variety of ligands were used to hydrogenate 73a, 74a-b, 75a-b, and 76a with moderate results. Steric interactions were magnified and that may explain why nearly all of the substrates in Scheme 15 give less than optimal results. A-methyl-A-phenyl-amine derived enamines 74a and 75a were resistant to hydrogenation where the analogous A-methyl-W-benzyl-amine-based enamines were completely converted with SimplePHOX ligand 77 with moderate enantioselectivity. 

Alkyl aryl ketimines were reduced with up to 99% ee (Scheme 8) [24]. The high enantioselectivity was not affected by the E Z ratio of the imines. For example, a 1.8 1 E Z mixture of the N-propylimine of 4 -methoxy-3-methyIbuty-rophenone was converted to the desired product in 97% optical yield. Hydrosilylation of the N-propylimine of cyclohexyl methyl ketone with a substrate to Ti molar ratio of 2,000 1 was completed to give the product in 98% ee [24]. N-Benzylimine of 2-octanone, a simple aliphatic ketimine, was reduced with 69% optical yield. The reduction of W-benzyl-l-indanimine gave the corresponding amine in 92% ee (Scheme 9) [24]. 

J)-2-Benzylamino-4-oxo-4-[(J )-l-phenylethylamino]butanoic Acid W-Benzyl-/V2-(r>-a-niethylbenzyl)-r>-asparagine, 1S Typical Procedure20 ... 

Scheme 2 Regioselective Synthesis of w-Benzyl Esters via COpper Complexes ...

Benda, G.I. Hiller, J.L. Reynolds, J.W. Benzyl alcohol toxicity impact on neurologic handicaps among surviving very low birth weight infants. Pediatrics 1986, 77, 507-512. 

W-Allyl, 895 W-f-Butyl, 896 W-Dicyclopropylmethyl, 896 W-Methoxymethyl, 897 W-Methylthiomethyl, 897 W-f-Butylthiomethyl, 897 W-Benzyloxymethyl, 898 W-2-(Trimethylsilyl)ethoxymethyl, 898 W-2,2,2-Trichloroethoxymethyl, 898 N-2- (p-Toluenesulfonyl) ethenyl, 899 W-f-Butyldimethylsiloxymethyl, 899 W-Pivaloyloxymethyl, 899 W-Cyanomethyl, 899 W-Pyrrolidinomethyl, 900 W-Methoxy, 900 W-Benzyloxy, 900 W-Methylthio, 900 W-Triphenylmethylthio, 901 W-f-Butyldimethylsilyl, 901 W-Triisopropylsilyl, 902 W-4-Methoxyphenyl, 902 W-4-(Methoxymethoxy)phenyl, 903 W-2-Methoxy-l-naphthyl, 903 W-Benzyl, 903... 

The reproducibility of rate and enantioselectivity can be a problem as described by the Marko group for the cationic catalyst [Rh(nbd)diphosphine] and W-benzyl-N-(l-methylbenzylidene)amine as model substrate [15]. Extensive efforts to find a correlation between purity of imine, water and oxygen content and the catalyst performance were not successful. However, these problems are not uncommon for enantioselective catalytic reactions but were not addressed any more in reports published at a later stage by Marko or other groups. 

Cationic Cetyl trimethyl ammonium bromide [CTAB]/w-alkanol w-Benzyl-w-dodecyl-w-bis(2-hydroxyethyl) ammonium chloride [BDB AC]/1 -hexanol [13-15] [16]... 

De Clercq and co-workers have revealed the importance of an W-benzyl group in their elegant thermal ring-closure of an ene carbamoylazide at the C-3 and C-3a positions of the (+)-biotin ring skeleton [82]. Upon heating, A-benzyl derivative 47 smoothly cyclized to the dehydro biotin derivative 49 in a good yield, while unsubstituted counterpart 46 gave only elimination product 48 (Fig. (17)). 

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