Aspects of catalytic hydrogenation with a soluble catalyst

The conversion of 23,24-dinor-chol-5-en-3β-ol into steroid hormones

“…l.OCi/mol) was synthesized from [7ae-3H]pregnenolone (3fl-hydroxy[7aC-3H]pregn-5-en-20-one) via the Wittig reaction with methylenetriphenylphosphorane, giving 23,24-dinor-[70c -3H]chola-5,20-dien -3,Bol (Sondheimer & Mechoulam, 1957). The latter was selectively hydrogenated at the 20-double bond by using the soluble catalyst tris(triphenylphosphine)rhodium chloride (Birch & Walker, 1966), giving 23,24-dinor-…”

Use of Transition Metal Complexes as Selective Hydrogenation Catalysts

“…The carbon-carbon triple bond is more readily reduced than an olefinic double bond, as has been shown in the stepwise reduction of acetylenic materials (Equation 4) (Birch and Walker, 1966a Among the olefinic centers which may be present in a molecule, the least substituted center need not be the one most easily reduced. However, the high degree of selectivity resulting from the extreme sensitivity of the coordinated substrate to its steric and electronic environment during hydrogenation is of particular utility in natural product chemistry-for example, carvone is readily reduced to carvolactone (Equation 5 ) (Birch and Walker, …”

“…AcO V (Equation 7) is not rapidly attacked by hydrogen (Birch and Walker, 1966a). The effect of conjugation in a hindered system would, therefore, appear to be somewhat beneficial.…”

“…I n instances where the reaction is successful, it avoids the formation of aromatic hydroquinone derivatives which are encountered in other reductive methods. Aldehydes are also resistant to hydro-0 0 genation, which allows the selective hydrogenation of unsaturated aldehydes to form saturated aldehydes (Equation 9) (Jardine and Wilkinson, 1967 halogen bond in allylic halides is hgdrogenolyzed to a lesser extent than over heterogeneous catalysts, making it possible to obtain fair yields of 3-phenyl-1-chloropropane from cinnamyl chloride (Equation 10) (Birch and Walker, 1966a). Groups which are not reduced include acid, ester, cyano, and aromatic functions (Abley and McQuillan, 1969;Walker, 1966a,b, 1967b;Evans et al, 1965;Horner et al, 1968a,b;Jardine et al, 1967;Jardine and Wilkinson, 1967;Knowles and Sabacky, 1968;O'Connor and Wilkinslon, 1969;Osborn et al, 1966).…”

Polymerizability of 1,3-Disubstituted 1,3-Butadiene and Preparation of New Alternating Copolymer

“…The 13 C NMR spectrum of the hydrogenated polymer showed 22.0, 44.7, 123.5, and 205.8 ppm which were assigned to carbons of -CH2-, -CH-, -CN, and -C=O, respectively (Figure 8). Since the hydrogenation of -C=C-OR (R, alkyl) with the Willkinson catalyst is repo'rted to lead to -C-C-, 14 II 0 the hydrogenated polymer is considered to be composed of -(-CH 2 -C-CH 2 -CH-)"-. The elemen-11 I 0 CN tal analysis of the polymer supports the polymers is being an alternating copolymer of ketene and acrylonitrile.…”