Page 934 - Advanced Organic Chemistry Part B - Reactions & Synthesis

910 O N O
HO –
CH N CNH – CH N
2 2
CHAPTER 10 3 2 RO Ref. 125
Reactions Involving
Carbocations, Carbenes,
and Radicals as Reactive
Intermediates O N O O N O
NaOH CH N
CH N C C NCH 3 2 2 Ref. 126
3

O N
KOH
N
CH N SO Ph CH 2 2 Ref. 127
3
2
The details of the base-catalyzed decompositions vary somewhat but the mechanisms
involve two essential steps. 128 The initial reactants undergo a base-catalyzed addition-
elimination to form an alkyl diazoate. This is followed by a deprotonation of the
-carbon and elimination of hydroxide.

N O N O +
X – OH X – RCH N N O H –H O RCH N : –
2
RCH NC RCH N C Z N :
2
2
Z H
OH HO –
Diazo compounds can also be obtained by oxidation of the corresponding hydrazone, 129
the route that is most common when one of the substituents is an aromatic ring.
HgO + :
Ph C NNH 2 Ph C N N –
2
2
:
Ref. 130
The higher diazoalkanes can be made by Pb(O CCH oxidation of hydrazones. 129
2
3 4
-Diazoketones are especially useful in synthesis. 131 There are several methods
of preparation. Reaction of diazomethane with an acyl chloride results in formation of
a diazomethyl ketone.
O O
+ +
RCCl + H C N N – RCCH N N –
2
The HCl generated in this reaction destroys one equivalent of diazomethane, but this
can be avoided by including a base, such as triethylamine, to neutralize the acid. 132

125
F. Arndt, Org. Synth., II, 165 (1943).
126 T. J. de Boer and H. J. Backer, Org. Synth., IV, 250 (1963).
127
J. A. Moore and D. E. Reed, Org. Synth., V, 351 (1973).
128
W. M. Jones, D. L. Muck, and T. K. Tandy, Jr., J. Am. Chem. Soc., 88, 3798 (1966); R. A. Moss,
J. Org. Chem., 31, 1082 (1966); D. E. Applequist and D. E. McGreer, J. Am. Chem. Soc., 82, 1965
(1960); S. M. Hecht and J. W. Kozarich, J. Org. Chem., 38, 1821 (1973); E. H. White, J. T. DePinto,
A. J. Polito, I. Bauer, and D. F. Roswell, J. Am. Chem. Soc., 110, 3708 (1988).
129 T. L. Holton and H. Shechter, J. Org. Chem., 60, 4725 (1995).
130
L. I. Smith and K. L. Howard, Org. Synth., III, 351 (1955).
131 T. Ye and M. A. McKervey, Chem. Rev., 94, 1091 (1994).
132
M. S. Newman and P. Beall, III, J. Am. Chem. Soc., 71, 1506 (1949); M. Berebom and W. S. Fones,
J. Am. Chem. Soc., 71, 1629 (1949); L. T. Scott and M. A. Minton, J. Org. Chem., 42, 3757 (1977).