Chemical Reviews Volume 92, Number 8
December 1992
Four-Membered Ring Compounds Containing Bis(methy1ene)cyclobutene or Tetrakis(methy1ene)cyclobutane Moletles. Benzocyclobutadlsne, Benzodicyclobutadiene, Biphenylene, and Related Compounds Fumio Toda' Deperbnsnt of ZndusMel Chemisby, Facue of Erwhmrhg, Ehkne Unhers&, Metsuyama 790, Japan
Peter Garratt' CMStopher Z q o M Laboratorbs, Department of Chemlsby, Unhersky CORlege London, 20 c)ordon Sbeet, London WClH OM, UK
Received September 9, 1988 (Re&&
Contents
Menuscdpt Reoelved M y 15, 1902 )
7 Introducfion
1 Introduction 2 Mis(methylene)cyciobutene Derivatives 2.1 3,eBis(methyiene)cyciobutene and NonbenzannelatedDerivatives 2.1.1 Preparative Methods 2.1.2 Structure and Spectroscopic Properties 2.1.3 Reactions 2.2 Cyciobutem1,2dione, 2,4-Bis(methylene)cyciobutanal,Mione, and NonbenzannelatedDerivatives 2.2.1 Preparative Methods 2.2.2 Structure and Spectroscopic Properties 2.2.3 Reactions 2.3 Tetrakis(methy1ene)clobutane and NonbenzannelatedDerivatives 2.3.1 Preparative Methods 2.3.2 Structure and Spectroscopic Properties 2.3.3 Reactions 3 Benzocyclobutadiene and Related Systems 3.1 Preparative Methods 3.2 Structure and Spectroscopic Properties 3.3 Reactions 4 Benzodicyciobutadiene Derivatives 4.1 Reactions 4.1.1 Oxidation 4.1.2 Addition 4.1.3 Complexes with Fe(CO)3 4.1.4 Reaction with Dienophiies and Dienes 4.1.5 Addition of Dichiorocarbene 4.1.6 Insertion of Heteroatoms 5 Biphenylene and Related Compounds 5.1 Preparative Methods 5.2 Structure and Spectroscopic Properties 5.3 Reactions 6 Conclusions
1685 1686 1686 1686 1688 1688 1689
1689 1690 1691 1692 1692 1693 1693 1694 1694 1695 1696 1696 1697 1697 1698 1699 1699 1700 1701 1702 1702 1704 1705 1705
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The 3,4-bis(methylene)cyclobutenegroup occurs in many chemical species. It is a strained entity in that sp2hybridization would require bond angles of 120° at each of the four carbons of the 4-membered ring. Nevertheless, 3,4-bis(methy1ene)cyclobutene (la) is iteelf formed by a t,hermalrearrangement (section 2.1) and is a stable, well characterized compound. Formally introducing a double bond to join the methylene atoms gives benzocyclobutene (2),5 a compound of considerably less stability. The bis(methy1ene)cyclobutene structure 2a is the most important of the contributing canonical structures, since structure 2b incorporates a cyclobutadiene moiety. Annelating a benzene ring to
2a
2b
3a
3b
- m-m /
4a
4b
4c
la gives bis(methy1ene)benzocyclobutane 3, and annelation to benzocyclobutadiene gives biphenylene (4). Both 3 and 4 are more stable than 2, and in both of these systems canonical forms containing the dimethylenecyclobutene are important but not exclusive, structures containing tetrakis(methy1ene)cyclobutane ([llradialene) moieties (3b,4c) making a major contribution. Benzocyclobutene is the correct,but confusing,name for 2, annelated systems ending in "ene" indicating complete unsaturation, unlike nonannelated nonaromatic systems. We prefer the name benzocyclobutadiene for 2 and w i l l u88 it throughout this review.
0 1992 American Chemlcal Society
1-
a l U W C 4 Reviews.
T&
1892.Vd. 82. NO. 8
FMioTodareceivedhisBache&'s. Master's.and Doota'sdeqees hwn Osaka University at Osaka Cny, Japan In 1856. 1858,and 1960,reSpecthrely.After stayheatOsaka Universityfatwryears as an Insbwtor and In United States for two years as a postdoctoral fallow. he obtained an Associate RofessorsMp at Ehlme UniversRy In 1966. He was promotedto full RofassorIn 1970.His researchhterestsarelntheareaofstrainedsmalMnocomD.
and Gunu
ulhrsslty h 1856 and. after a period h teachhrg and a year wllh J.K.N.JonakCanada,obtalnedePh.D.wlthT.J.KakatColunbla UntwemHy h I9M. He then retuned to the UK as a NATO F d b w to wak with F. sonchelmsr at Cambridge UnhwsHy and was appohted a UniversRy D a m s t r a t a and F d b w of Flhwllllam h 1866. He moved to universny cokge ond don h 1867 and was made a Reader In 1974. His ament research lntereata arehatrahedcarpands,aganicconducmrs.~ofenzymes early h the pyhldlne blosynthetk pathway. ion channel blockers. and probing the structure of the melatonin receptor.
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Extendingthe number of bm(methy1ene)cyclobutene structures from biphenylenecan be done in two modes, linearly or angularly, as in 5 and 6, respectively. In 5 a t least one 3,4-bis(methylene)cyclobutenestructure must be retained (5a,c), whereas in 6 a structure with only tetrakis(methy1ene)cyclobutane moieties can be accommodated (6a).
5a
related structure, and will examine the limits that can be placed on these structural entities and the effects that they engender. Compounds of this type were reviewed in the classic text of Cava and Mitchell,' and certain aspeda of the chemistry of such compounds may be found in other
2n-kk(ln6+th~)9clabilt~~afhw
5b
2.1 S,cek(methylN)cycWyclobut.m a d Nonhannolated Derlvaihre8 2.1.1 Preparath,e Meltlods
5c
68
6b
60
4-Methyleneeyclobuten-3-one(7), cyclobutene-3,4 dione (E), 3,4bis(methylene)cyclobutaue-l,2-dione(9), and 2,4bis(methylene)cyclobutane-l,3-dione(10)have related structures with similar strain effeds. Again, these entities can participate in benzannelated structures such as 11 and 12, but as with bis(methy1ene)benzocyclobutane, other canonical structures make important contributions.
7
9
10
This review w i l l examinethe behavior of compounds possessingthe bm(methy1ene)cyclobutene moiety, or a
3,4Bis(methylene)cyclobutene (la),although experiencing considerablebond-angle strain, is well known, b e i i initially prepared, albeit in only 1%yield, by Blomquist and Maitlis in 1961through the Hofmann degredation of 3,4bis[(trimethy~o~o)methyl]cyclobutenedihydroxide.' Currently, the main synthetic route to la and substituted derivatives involves the electrocyclicrearrangement of hexa-1,2,4,5-tetraene or a substituted derivative. Thus la can be derived thermally from 13a.6 The tetramethyl derivative l b can be similarly prepared from the corresponding tetramethylhexatriene 13b,a higher temperature being required (250 "C, cf. 150 0C).6J The meso-diallene 14 rearranged slowly a t 150 OC but much more rapidly in boiliig THF in the presence of copper(1) chloride? in both cases to give 15 by conrotatory ring closure. The same catalytic effect of copper(1)was also observed in the formation of la.' Thefmt, a n d s t i l l p r o b a b l y t h e ~ p r e ~ t i ~ r o u t e to 3,4bis(methylene)cyclobutene (la) wan by the thermalrearrangementof hexa-1,Myne (lb),the initial C3,31 sigmatropic rearrangement to 13a b e i i much slower than the subsequent electrocyclic ring closure of 13a to"'.al
Fou-4
Chemlcal Reviews, 1002, Vol. 02,
Rhg Compounds
?
R
13aR=H bR=Me
16
laR=H bR=Me
No. 8 1887
in the gas-phase reaction and 24.076.0 in solution. Both produds are formed in a conrotatoryprocess, compound 26 being much less sterically crowded than compound 25.
-
(H
Ph
.,I.
Bu'
{Me \ Bu'
+
4;
H
BU'
H
25
24
26
tie 15
14
Thermolysis of the dibromotetraene 18, readily prepared from the diol 17 by treatment with HBr, gave the dibromobis(diphenylmethy1ene)cyclobutene(&)in almost quantitative yield.12 The dichloride 19b could be similarlyprepared, and the cyclobutenylhalides were reactive, the bromine in 19a being readily replaced by hydrogen to give 19c by treatment with LiAlH4. Coupling of the bromodene 20 with copper(1)chloride gave a mixture of the bis(methy1ene)cyclobutenes 22 and 23, presumably via the bisallene dimer 21.13 Ph
R,--' h: ' , HO'
p
X h
OH 17
P Ph h
5
w h X Ph 18X=Br x = CI X=H
The mechanism of the rearrangement of 1,5-hexadiene was studied by Henry and Bergman,lSwho showed that, after rearrangement, the deuterium atoms of 1,6dideuteriohexa-l,5-diyneappeared in the 1,2-positions of 3,4bis(methylene)cyclobutene (la). At higher temperatures la rearranged to benzene and fulvene. Treatment of the propargyl chlorides27 with tetrakis(triphenylphosphorany1)nickelin benzene under argon gave the 2-dipropenylcyclobutenes(281." 2,7-Dimethylocta-2,3,5,6-tetraene (29) gave a trimer under these conditions but a mixture of 3,4-di-2-propylenecyclobutene (28, R = H) and 3,4,7,&tetra-2-propylenecycloocta-1,5-diene (30) on reaction with dicycloodadienenickel.18
'X 28 R = H, Me
27 R = H, Me Ph 19a X = Br bX-CI CX=H
p;,
Bu'
1
E &
Ph 21
20
Bu'
BU'
+
ph*ph Ph
Bis(methy1ene)cyclobutene (la)can also be prepared by the retro-Diels-Alder cleavage of 31 at 425 OC, the latter being prepared in three steps from the DielsAlder adduct of quadricyclane with maleic anhydride.I9
& - Q +
