Weygand/Hilgetag Preparative Organic Chemistry

Addition of hydrogen to C—C bonds and aromatic systems 15
3-(2-Nitrovinyl)indole (15 g) is extracted during 8 h from a Soxhlet thimble into a flask
containing LiAlH4 (15 g) in anhydrous ether (300 ml). The mixture is then treated with water
(80 ml), slowly and with cooling, and filtered. The ether solution is separated, dried over
sodium sulfate, and saturated with hydrogen chloride. Tryptamine hydrochloride (12.7 g)
is thus obtained, melting at 249-250° (decomp.) after recrystallization from methanol-ethyl
acetate.
Other complex metal hydrides can only rarely be applied to reduction of
C=C bonds. Sodium borohydride, which can be used in aqueous-alcoholic
solution, seems not normally to attack ethylenic bonds. A few cases only of
partial reduction of cyclic iminum salts 96 and of selective reduction of unusually
activated ethylenic bonds 97 have been reported. However, some polynitro
aromatic compounds, e.g., 1,3,5-trinitrobenzene, can be converted in high
yield with saturation of the aromatic system into nitrocyclohexanes or nitrocyclohexenes.
98 Sodium hydridotrimethoxyborate has proved valuable as a
mild reducing agent for preparation of a series of nitroparaffins from nitroalkenes."
Monographs 100 should be consulted for comprehensive studies of these reductions.
d. Reduction by diimine
An increasingly important place in recent literature is being taken by papers
on the reduction of olefinic double bonds by hydrazine in conjunction with
oxidizing agents such as oxygen, peroxides (particularly in the presence of
catalytic amounts of Cu 2+ ), mercuric oxide, hexacyanoferrate, iodine,
etc 101,102 jkjg process saturates not only conjugated but also isolated double
bonds. Diimine is formed as the actual hydrogenating agent; it is a short-lived
species which can be obtained for this purpose also from other sources. 101 ' 102
The following methods of obtaining it are important, as well as the oxidation
of hydrazine: thermal decomposition of arenesulfonohydrazides 103 * 104 and
9,10-anthracenediimine; 105 spontaneous decarboxylation of azodicarboxylic
acids on acidification of their salts; 103 ' 104 ' 106 and alkaline fission of chlor-
96 W. Awe, H. Wichmann, and R. Buerhop, Chem. Ber., 90, 1997 (1957); R. E. Lyle,
R. E. Adel, and G. G. Lyle, /. Org. Chem., 24, 342 (1954); N. Kinoshita, M. Hamana, and
T. Kawasaki, Chem. & Pharm. Bull. {Tokyo), 10, 753 (1962).
97 J. Fajkos, Collect. Czech. Chem. Commun., 23, 2155 (1958); M. Miyano and M.Matsui,
Chem. Ber., 91, 2044 (1958); J. Knabe, P. Herbort, and N. Ruppentahl, Arch. Pharm., 299,
534 (1966).
98 T. Severin and R. Schmitz, Chem. Ber., 95, 1417 (1962).
99 H. Shechter, D. E. Ley, and E. B. Robertson, Jr., /. Amer. Chem. Soc, 78, 4984 (1956).
100 N. G. Gaylord, "Reduction with Complex Metal Hydrides," Interscience Publishers,
Inc., New York, 1956; (b) A. Hajos, "Komplexe Hydride und ihre Anwendung in der
organischen Chemie," VEB Verlag der Wissenschaften, Berlin, 1966.
101 Review: S. Hmrig, H. R. Miiller, and W. Thier, Angew. Chem., 77, 368 (1965).
102 (a) A. Fiirst, R. C. Berlo, and S. Hooton, Chem. Rev., 65, 51 (1965); (b) B. F. Aylward
and M. Sawistowska, Chem. & Ind. (London), 1962, 484.
103 E. E. van Tamelen, /. Amer. Chem. Soc, 83, 3725, 3729 (1961).
104 S. Hunig, H. R. Miiller, and W. Thier, Angew. Chem. Int. Ed. Engl, 2, 214 (1963);
Tetrahedron Lett., 1961, 353.
105 E. J. Corey and W. L. Mock, /. Amer. Chem. Soc, 84, 685 (1962).
106 E. J. Corey et al, Tetrahedron Lett., 1961, 347; /. Amer. Chem. Soc, 83, 2957 (1961)