9 52 Formation of new carbon-carbon bonds
Cyanohydrins react with hydrocarbons with loss of water and formation of
nitriles; thus pyrocatechol dimethyl ether and veratraldehyde cyanohydrin
give a good yield of bis-(3 5 4-dimethoxyphenyl)acetonitrile:
669
.OCH 3
CH 3 Cf "-^ HC- \^ -0CH3 CH,(T ^^C^^^OCH,
Ethyl cyanoacetate is converted by acetaldehyde cyanohydrin in the presence
of sodium alkoxide into ethyl 2,3-dicyanobutyrate in 80% yield.
670
- Alkylation by aldehydes
Only one new carbon-carbon bond is formed by the methods described
above: two new carbon-carbon bonds are formed simultaneously if in such
condensations the alcohol is replaced by a carbonyl compound, e.g.:
2RH + R'CHO > CHR 2 R' + H 2 O
Such reactions, which will not be discussed further here, include the formation
of diarylmethanes from an aldehyde and two molecules of an aromatic hydro-
carbon, of triphenylmethane derivatives from an aldehyde and two molecules
of an aromatic amine, and of phthaleins from phthalic anhydride and two
molecules of phenol or resorcinol.
This type of reaction includes also the formation of diarylacetic esters from
glyoxalic esters and aromatic compounds, yields again being good.
671
Preparative importance attaches further to Hellmann and Dietrich's so-
called asymmetric three-carbon condensation, in which, within certain limi-
tations, two different compounds containing active methylene groups are
linked together by formaldehyde with formation of two new carbon-carbon
bonds. For example, dibenzoylmethane, dimethyl (acetylamino)malonate, and
formaldehyde afford an 88% yield of dimethyl oc-(acetylamino)-a-(2,2-di-
benzoylethyl)malonate [1 -(acetylamino-3-benzoyl-4-oxo-4-phenyl-1,1 -butane-
dicarboxylate].
672
(C 6 H 5 CO) 2 CHCH 2 C(COOCH 3 ) 2
NHCOCH3
A series of otherwise inaccessible compounds can be prepared in this
- CWoromethyIation271b'^674
A reaction:
ArH + HC1 + CH 2 O > RCH 2 C1 + H 2 O
(^669) A. Muller and M. Vajda, /. Org. Chem., 17, 800 (1952).
(^670) A.Higson and F.J.Thorpe, /. Chem. Soc, 89, 1455 (1906); R. P. Linstead and
M. Whalley, 671 /. Chem. Soc, 1954, 3722.
G. Werber, M. Ruccia, and A. Sabahni, Ann. Chim. {Rome), 50, 1438 (1960); G. Wer-
ber and M. Riccia, Ann. Chim. {Rome), 50, 1368 (1960); G. Werber and F. Maggio, Atti
Accad. ScL Lett. Arti Palermo, [4], 20, 15 (1961).
(^672) H. Hellmann and D. Dietrich, Ann. Chem., 632, 73 (1960).
(^673) H. Hellmann, D. Dietrich, and K. Muller, Ann. Chem., 656, 70 (1962) and earlier
papers. 674
R. C. Fuson and C. H. McKeever, Org. Reactions, 1, 63 (1942).