Syntheses of dispiro[2.1.4.1]decane and dispiro[2.0.3.3]decane

Article abstract of DOI:10.1016/S0040-4039(00)01577-X

Efficient syntheses of the hitherto unknown hydrocarbons dispiro[2.1.4.1]decane and dispiro-[2.0.3.3]decane have been realized through reaction sequences involving spiro[3.4]octan-2-one and spiro[3.4]octan-5-one as key intermediates. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4039(00)01577-X

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 9441–9443
Syntheses of dispiro[2.1.4.1]decane and dispiro[2.0.3.3]decane
†
John E. Baldwin,* Maryann E. Keene and Rajesh Shukla
Department of Chemistry, Syracuse University, Syracuse, NY 13244, USA
Received 18 August 2000; revised 11 September 2000; accepted 12 September 2000
Abstract
Efficient syntheses of the hitherto unknown hydrocarbons dispiro[2.1.4.1]decane and dispiro-
[
2.0.3.3]decane have been realized through reaction sequences involving spiro[3.4]octan-2-one and
spiro[3.4]octan-5-one as key intermediates. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: cyclopropanes; hydrocarbons; polycyclic aliphatic compounds; spiro compounds.
Five of the eleven possible dispirodecanes incorporate one three-membered, one four-mem-
bered, and one five-membered ring (1–5). These five hydrocarbons combine the comparatively
large strain energies and thermal reactivities associated with cyclopropane and cyclobutane
sub-structures with the geometrical limitations imposed by the cyclopentane element and the
spirocyclic linkages. These features in various geometrical dispositions offer novel opportunities
for exploring just how subtle mutual accommodations of structural constituents may influence
ground-state heats of formation and favored conformations, and the rates of alternative thermal
isomerization and fragmentation reactions. The influences of conformational restrictions on
1
access to and reactivity of thermally generated diradicals derived from 1 to 5 as cyclopropane
or cyclobutane rings cleave homolytically may be particularly revealing.
The first of these five isomers, dispiro[2.1.3.2]decane (1), was synthesized for the first time only
2
last year; efficient preparations of the second and third hydrocarbons in this set,
dispiro[2.1.4.1]decane (2) and dispiro[2.0.3.3]decane (3), are now reported.
*
Corresponding author: Tel: 315-443-3743; fax: 315-443-4070; e-mail: jbaldwin@syr.edu
January 2000 Undergraduate research intern from Wells College, Aurora, NY 13026.
†
0
040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)01577-X

9442
From the many possible synthetic approaches to these polycyclic hydrocarbons a common
strategy was selected, based on the generally reliable two-step transformation of a cycloalkanone
to a methylenecycloalkane to a cycloalkanespirocyclopropane, a sequence used in one of our
2
two syntheses of dispiro[2.1.3.2]decane (1). Thus the four-step sequence from methylenecy-
clopentane to dispirodecane 2 outlined in Scheme 1 was selected and realized. It takes advantage
of a readily accessible starting material and a brief sequence of suitable well-established
reactions.
Scheme 1.
Spiro[3.4]octan-2-one (8), the key intermediate, has apparently been made only once before,
3
inefficiently, through the photodecarboxylation of 3,3-tetramethyleneglutaric anhydride. The
alternative preparation of Scheme 2 provided ketone 8 much more conveniently. Methylenecy-
4
clopentane was combined with dichloroketene generated in situ to give the (2+2) cycloaddition
product 1,1-dichlorospiro[3.4]octan-2-one (7) with very high regioselectivity and fair yield, 78%.
5
The dichloroketone was reduced with zinc in acetic acid to provide the known spiro[3.4]octan-
3
,6
2
-one (8) in 63% yield. A Wittig reaction converted this ketone in 80% yield to 2-methylene-
7
8
spiro[3.4]octane (9). Finally, a Simmons–Smith reaction employing activated zinc rather than
the more traditional zinc–copper couple afforded dispiro[2.1.4.1]decane (2). It showed the
expected six resonances in the C NMR spectrum, the fewest to be anticipated from the
1
3
9
dispirodecane isomers 1 to 5.
Scheme 2.
The tactically identical preparation of dispiro[2.0.3.3]decane (3) outlined in Scheme 2
depended on access to spiro[3.4]octan-5-one (11), a long known and readily accessible com-
1
0
11
pound. It was made through an epoxidation of bicyclobutylidene (10) followed by a BF3
12
etherate catalyzed isomerization to afford ketone 11. A Wittig condensation converted 11 into
-methylenespiro[3.4]octane, a known olefin. A cyclopropanation then provided the target
hydrocarbon 3.
12
5
1
3,14
These preparations of dispirodecanes 2 and 3 are quite direct, reasonably efficient, and
amenable to scale-up. They demonstrate the attractive features of the routes outlined in Schemes
1
and 2 and provide clean, isomer-free samples of these polycyclic hydrocarbons. With these
syntheses and characterizations, three of the five dispirodecanes 1 to 5 are now in hand and
available for comparative studies of thermal reactions and reactivities. Efficient preparations of

9443
the remaining two isomers in this set, dispiro[3.0.4.1]decane (4) and dispiro[2.0.4.2]decane (5),
are currently being developed.
Acknowledgements
We thank the National Science Foundation for support of this work through Grant
CHE-9902184. This contribution is dedicated to Professor Harry H. Wasserman on the occasion
of his 80th birthday, with special appreciation of his artistic gifts, his contributions to the
chemistry of cyclopropanone equivalents, and his total syntheses of the polyamine alkaloids
(
±)-chaenorhine and (±)-O-methylorantine.
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3
+
2
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1
13
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1
13
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+
2
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1
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1
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13
3. Dispiro[2.0.3.3]decane (3): H NMR l 0.2–0.3 (m, 2H), 0.4–0.5 (m, 2H), 1.50–1.90 (m, 12H); C NMR l 8.3,
+
1
5.7, 21.1, 28.4, 29.4, 33.7, 39.2, 48.3; MS m/z 136 (M ), 121.
1
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.