Reduction by Hydrogen, Dissolving Metals, and Electrolysis

Hydrogenolysis of 6,6-dichloro-l-methylbicyclo[3,l,0]hexane causes cyclo-propyl-allyl rearrangement and monodechlorination without saturation. In the presence of ethylenediamine, the exo-monochlorobicyclic compound was obtained without rearrangement. Hydrogenolysis of both isomers of (297) with Raney nickel has been investigated in the presence of a wide range of nucleophilic additives. The observed reactions are dechlorination and production of methylcyclohexane in proportions which are determined by 

K Takenaka and K Isogai, Nippon Kagaku Kaishi, 1972, 662 Chem. Abs., 1972, 76 140019). 

R Kano, K Kobayashi, and K. Isogai, Bull Chem. Soc. Japan, 1972,45, 1926. 

Gassman and Creary have reported that the centra bond of succinic esters can be cleaved with sodium in liquid ammonia. This method gives dimethyl glutarate from dimethyl cis- and trans-cyclopropane-l,2-dicarboxylates. The C-1—C-2 cleavage of a 1,2-diphenylcycIopropane which is part of a more complex, tricyclic compound has been effected by lithium in ammonia. Although it is known that lithium-ammonia reduction of a cyclopropyl ketone cleaves the bond which will allow tlw best overlap with the carbonyl Tt-system, the steric course of protonation at the f(-carbon has not, until recently, been known. Reduction of (301) at — 78 °C gives (302X the product with inversion, and (303), 

A review of the stereochemical consequences of electrochemical reduction including dehalogenation of cyclopropyl halides has been published. Polaro-graphic reduction proved to be the most convenient method of introducing hydrogen (or its isotopes) into (305).  

Reduction by Hydrogen, Dissolving Metals, and Electrolysis.—new apparatus has been described which permits the detailed study of catalytic reactions at single-W. Kirmse, J. Alberti, and H.-G. Varbelow, Chem. Ber 1974,107, 2788. 

During hydrogenolysis of isopropylcyclobutane over the Group VIII noble metals, cleavage of all the ring C—C bonds occurs. Selectivity of cleavage opposite the substituent increased in the series Pd, Pt, Ir, Rh, Ru, but the last three metals also catalysed 

Lumitestosterone acetate (511) was found to hydrogenolyse with palladium in ethanol to a mixture of (512 R = R = R = H R = Ac), (512 R = OEt R2 = R3 = H), and (512 R = H R R = H or OH R = Ac). With Raney nickel, a small amount of a fourth product (513) was also formed. The formation of the 5a product (512) is surprising, since models suggest a P approach to be more favourable for the lOa-methyl steroid (51IX and it was therefore proposed that the hydrogenolysis proceeds by an initial isomerization to (514). 

Methyl migration has been noted in the hydrogenolysis of (515) and related compounds over palladium and platinum catalysts. Cleavage of the three-membered ring occurs on catalytic hydrogenation of prazepam (516X in contrast to electrolysis which reduces only the imine function.  

The reduction of acetylcyclopropanes by metal-ammonia solutions involves cleavage of the cyclopropane ring. The overall reaction requires two electrons, and substi- 

---