Organic Reactions Volume 4 - Sciencemadness Dot Org

68 ORGANIC REACTIONS
it is not the acid of IX). 2 Various 1-aryl-l-methylbutadienes were employed
also with acrylic acid and with crotonic acid.
The derivatives of hydrobiphenyl obtained by the second method
have been used quite extensively in the synthesis of dibenzopyrones and
their hydro derivatives, 16 ' 17 hydrofluorenones/ 3 ' 18 and hydrophenanthridines.
18 o~Methoxy cinnamic acid (cis and trans) and the corresponding
hydroxy acid react readily with 2,3-dimethylbutadiene, unsatisfactorily
with isoprene, and not &t all with butadiene. The hydropyrone
(XXIII) obtained by the demethylation and lactonization of XXII
O O
Il Il
0—C 0—C
XXIII XXIV
(R = R" = H, R' = OCII3) with ethanolic potash is isomeric with
that from the interaction of coumarin with 2,3-dimethylbutadiene under
forcing conditions (260°). These hydropyrones are probably diastereomers,
for on dehydrogenation they yield the same benzopyrone (XXIV).
The adduct from o-methoxycinnamic acid and isoprene is considered
to be XXV, for the analogous reaction with 2,6~dimethoxy-4-n-amylcinnamic
acid gives solely XI (except in one instance, which it has not
been possible to duplicate, when the isomeric adduct was isolated in
43% yield). Methyl o-veratrylidenepyruvate reacts normally with
cyclopentadiene, but the adduct with butadiene could not be isolated.
Dimethylhexahydrofluorenone and many of its substitution products
(XXVI) were obtained by the addition of 2,3-dimethylbutadiene to
cinnamic acid (or ester) and to substituted cinnamic acids (3,4-dimethoxy-
and 3,4-dimethoxy-6-nitro-) followed by cyclization of the acid
chloride of the dihydro derivative of XXII. These hexahydrofluorenones
have been converted to octahydrophenanthridines (XXVII)
by ring enlargement of XXVI (hydrazoic acid) to hexahydro-9-phenanthridones,
followed by conversion to the thio analog (phosphorus
pentasulfide) and electrolytic reduction at a lead cathode.
16 Adams, MePhee, Carlin, and Wicks, J. Am. Chem. Soc, 65, 356 (1943).
17 Adams and Carlin, J. Am. Chem. SoC1 65, 360 (1943).
18 Sugasawa, Kodama, and Hara, J. Pharm. Soc. Japan, 60, 356 (1940) [C. A„ 34, 7291
(1940)].