B. Halton / Tetrahedron Letters 47 (2006) 1077–1079
1079
(7%) yield (Scheme 3). A second component, obtained as
References and notes
a different yellow crystalline C24H14 hydrocarbon (m/z
302) in 12% yield is tentatively proposed as dibenz-
[a.e]aceanthrylene (15) from its physical characteristics
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and H NMR spectroscopic data that agree fully with
those reported by Cho and Harvey,19 and subsequently
refined by them with Kim in 1993.20 Again the identity
of the low field singlets at d 8.26 (H9) and 9.03 (H14)
with those reported (d 8.24 and 9.00, respectively)
together with identical chemical shifts and coupling pat-
terns for the remaining 12 protons supports the assign-
ment. Whereas a straightforward mechanistic pathway
exists for the formation of 12 via 1 and 11 (Scheme 3),
with the only variable being the point at which cyclo-
dehydrogenation between the two phenyl substituents
takes place, no such easy-to-describe pathway exists
for the 2!15 transformation.
Not all of the C24H14 hydrocarbon products from 1 and
2 were able to be separated by the facilities available.
However, it seems clear that automerization23 in ana-
logy to that of acephenanthrylene itself24 could trans-
form the initial products 7 and 12 into the known25,26
naphth[1,2-e]acephenanthrylene (9), and its [2,3-e] iso-
mer (14),27 respectively, as shown in Schemes 2 and 3.
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While the results recorded here are open to further
refinement, it is clear that the simple diarylmethylidene-
cycloproparenes readily transform into acephenanthryl-
enes upon FVT. The area is open to anyone who wishes
to follow so that the full range of products may be
delineated.
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Acknowledgements
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I wish to express my sincere thanks to my longstanding
friend and colleague, Professor Roger F. C. Brown, and
his former colleagues of the Chemistry Department at
Monash University (Melbourne) for the provision of
facilities and their genial hospitality during a leave of
absence from Victoria University some years ago.
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Supplementary data
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