[Reprinted from Inorganic Chemistry, 15,466(1976).]
Copyright 1976 by the American Chemical So-iety and reprinted by permission of the copyright owner.
Contributionfrom the Departmentof Chemistry,
Massachusetts
Instituteof Technology,
02139
Cambridse,Massachusetts
ConvenientPreparationsof
and
1,2,3,4,5-Pentamethylcyclopentadiene
I -Ethyl-2,3,4,5-tetramethylcyclopentadiene
DavidFeitlerandGeorseM. WhitesidesReceitted
Mav 19.1975
A tc 5 0344S
(MesCp) anion is a useful
Pentamethylcyclopentadienyl
congenerin transitionmetal chemistry.l'2
cyclopentadienyl
Investigation
of MesCpmetal compoundshasbeenhindered
(l).t':
of pentamethylcyclopentadiene
by the inaccessibility
The mostcommonlyusedsynthols: (SchemeI) is inconvenient
have
and expensive
and the optimalexperimentalconditionsa
not beenwidely disseminated.Although specializedreactions
prepayield MesCpM derivatives,5.6
no general,large-scale
rationof pentamethylcyclopentadiene
or otherpolyalkylated
derivativeshas beenavailable.
Burgeret al. recentlyreportedtwo shortsyntheses
of MesCp
(SchemeII).7
preparations
whichare practicalfor large-scale
The startingmaterialin the first of thesesyntheses,
hexamethyl(Dewarbenzene)(2) is expensive
and sensitive.We
have repeatedthe cleavageof 3 to I following the reported
methodTon a preparativescaleand foundit to be an efficient
and convenientmethod. The secondprocedureprovidesan
(4), an ininexpensive
route to tetramethylcyclopentenone
termediatealsousedin the previoussynthesis.3We havenot
reproducedthe secondroute.
Here we describea fourth route to I and a particularly
convenientpreparationof I -ethyl-2,3,4,5-tetramethylcyclopentadiene(9) (SchemeIII). This synthesis
of I is basedon
the work of Coniaeand Eaton.l0 2-Butyltiglate (6) is prepared
eitherby acid-catalyzed
esterificationof tiglic acid (5) or by
allowingtigloyl chlorideto reactwith 2-butanol. Compound
(4)
6 is cyclizedand dehydratedto tetramethylcyclopentenone
usingI : l0 solutionof PzOsin methanesulfonic
acid.l0 This
mediumprovedsuperiorto PPA for this cyclization(seethe
ExperimentalSection).Additionof methyllithiumto 4 and
dehydrationof the resulting alcohol to I follow previous
syntheses.3.7
The synthesis
of 9 beginswith dimerizationof
(7) by refluxing
3-pentanone
to 4,5-dimethyloctane-3,6-dione
with leaddioxide.lI This procedureis both more convenient
and saferthan that requiringacetylperoxide,l2
and it is not
necessary
to isolate7. After simpledistillationof excess
3-pentanone,
a base-catalyzed
internal aldol condensation
converts7 to 8; additionof methyllithiumand dehydration
affords9. Compound9 was characterized
by NMR spectroscopyand by conversion
to ethyltetramethylcyclopentadienyl
(EtMe+Cp)derivatives
of titaniumandiron ((EtMe+Cp)zTiClz
and (E tMe4C p)uFe).
The relativemeritsof thesenew methodsfor preparation
of pentaalkylcyclopentadienes
are basedon cost and convenience.The mostconvenientof thesefour preparationsfor
large-scale
work is that leadingfrom 3-pentanone
to 9 (method
Notes
InorganicChemistry,Vol. 15,No. 2, 1976 467
S c h e m eI . S y n t h e s i so f P e n t a m e t h y l c y c l o p e n t a d i e n (cl ) B a s e do n
B u t e n y l l i t h i u m ( M e t h o d 1)
"o
OHH
ErlLr
2 74cio
/
\
/
(3)
S c h e m eI I I . N e w S y n t h e s e so f P e n t a m e t h y l c y c l o p e n t a d i e n e
and E thy lte tramethylpen tadiene (9)
Method 4
\/
n
cro3-pv'dine
-/,/.tt,'
\\ //
3 Hzo
/
7\o/o
(
)
85%
\a^ot
\
il
+r
ll
-d\\il
/\
H C 0 2 H ,H 3 P O a
85%
I c H 3 L i ,E r 2 0
2. H', -H2O
-a,4,-
,\
tl
'/a
ili
P205-cH3so3H
4 hrs, 25'
6
,
.-............--...".............._
\il
85%
-
2SOa'A
tt"'"
H
0
roru€no \rA",
2 - butonol
)
n
n
il
o
,H'
tl
I
(Overall
r#
I CH3Lr
\r^.t,r
2Iz
yield 46%)
S c h e m eI I . S y n t h e s e so f P e n t a m e t h y l c y c l o p e n t a d i e n e
R c p o r t ed
by Burgeret al.?
Method 5
Method 2
z-c,-ceHoceHs.
\44
HocH2cH?oH.
*::?- AO
\-l-f
-tfl
t-r"-',--a
I
(overall yield 247r,on
preparative scale)
Method 3
ll
\-t'\'r-,'
tl
->t-
-t1
*=;;
il
)a'
)
0
tl
il
-,\.
oH-:d
-..,[--..
tl
,,,\-
o.,\
H2SO4, H2C02
38"/"
0
I
(ovcrall yield B')/,)
PbO2,
A
M € O H ,K O H
3 8 % ( b o s o do n p b O z )
l*.-.
a
I
=(}--
c H 3 t , E r z0
? iz, -A?o
5 ) . S t ar t ingm at e ri a l sa re i n e x p e n s i vaen d th . p r o..dL,r.i ,
eas ilyc ar r iedou t o n a s c a l eth a t y i e l d s 1 0 0 -2 00g of 9.
A lt houghor gano m e ta l l idce ri v a ti v eos f E tM e + Cpl ack the
a es t het ics y m m e trya i i o rd e d b i ' M e s C p , th e y have the
c o n r p e n s a t i n ga d v a n t a g e o f h i g h e r s o l u b i l i t y
((Et\{e+Cp):TiCl:is solublein bothtolueneandhexanewhile
(M e: Cp) : T iCl: is i n s o l u b l ei n th e s es o l v c n ts )and l ow er
m e l t i n g p o i n t s ( C p : F e , 1 l 1 o : ( M e s C p ) : F e ,2 9 1 - 2 9 5 " ;
(E t M er Cp) : F e,I 4 5 o ;C p :T i C l :,2 8 9 -2 9 1 :o(Me -sC p):Ti C l :,
: ,0 0 - 2 0 "1) .
2 73 " ; ( E t M e + C p ) : T i C l 2
Hex am et hl' l( D e w abre n z e n e(1
) ) i s n o t a n i n h erentl yexpens iv em at er iala n d re d u c ti o no f i ts c u rre n tp r i ce w oul d
u nques t ionably
r e n d c rme th o d2 th e b e s tro u teto l . B oth
methods2 and 4 produceI in comparablei'ields(24o/o
and
r es pec t iv cl yb).u t me th o d4 h a sth e d i s a d v antage
that
3 4026,
a n addit r onals t e pi s re q u i re d .T i g l i c a c i d i s , h o wever,l ess
e x pens r vtehan hc x a mc th y ' l (D e wbaer n z e n e ).M e thod 1 i s
clearl,vlcssconvenienl.
as a procedureto I than are methods
2 and 4. W e har e a ttc mp te dto p re p a re2 -b u ty lt i gl ate(6)
d i r ec t lyI' ' r om2- b ro m o -2 -b u te ncea,rb o nm o n o x i de,and 2ref H e c ke t a l .l r b u t havenot
b ut anolf ollowingth e p ro c e c l u o
b eenablc t o pr ot l u c emo rc th a n tra c ca m o u n ts .
A ll of t hc r nc t h o dds i s c u s s ehda v ep a rti c u l a ra ppl i cati ons
pr e p a ra l to r)
a s I ar ge- s c ulc
me th o d sfo r p e n ta a l kyl ated
cyc l o p c n t a d i c n eSsi.n r m e t r i c acly c l o p c n t a d i e n
ae
r esa v a i l a b l e
I
CH:Lr
2rz
2
( e xc c s s )
0
o
0
0
O
I
(overall yield 34%)
4
/'8
(mi-rtureof isomers)
9
(overall yield 28'/n)
from the appropriatestarting materialsin methods3-5.
Varyingdegrees
of substitution
may be inducedin method3
by variationsof aldehydeand/or ketoneusedand in method
4 by useof analogues
of tiglic acid and 2-butanol.Method
5 generates
a productof lower symmetrythan Me.sCp.Of
course.substituents
may be varied in derivativesmade by
methodsI .sbv the additionof alkyllithiumcompounds
other
than methrllithiumto the tetraalkylcyclopentenone,
although
stcrichindrance
mav becomea problemwith the morehighly
s u b s t i t u t ecd)c l o p n
etenones.
\\' c notc i i nal l i that the procedurefor prepar at ionof
rnctal l occnes
usi ngl rthi umcycl opentadi eni given
de
in t he
Experimcntal
Sectionis superiorto thosepreviously
reported
and i s appl i cabl e
to pentamethyl cycl openta diene
as well. la
Experimental
Section
Thcfbllorirng
rvere
chemicals
obtained
fromtheindicated
suppliers:
ti gl i caci d.3-pentanone.
thi onvlchl ori de.
methan csulf onic
acid
) :: O . t V a l l i n c k r o d t2) ;- b u t a n o l
( p r a c t i c aglr a d c )( [ : a s t m a nP
( . \ l d r i c hr)n. e t h i l l i t h i u( innrE t : O )a n dt i t a n i u m
( Ael f a ) :
trichlorid
pol yphosphori
l eaddi ori dc(Fi schcr):
acicd(MC B ).l r s pect rwer
a e
takenusi nga P [: Modcl567spcctrophotometcr.
andNM R spect r a
usi nga V ari anT-60spectromcter.
Mcl ti ngpoi nts,
bo ilingpoint s.
andpressures
areuncorrected.
Elcmental
werepcrformed
:rnalyses
bv R obcrtson
Fl. orham
l -aboratorl
P ark.N .J. B othMesCpH
and
-.10o.
shoul
d
E tMctC pl
-l
bc
stored
at
-figlate
(6). \{ethodA. A mixturc
2-Butyl
oi 400nl ol'2-butanol,
. 1 0 0n r l o l ' t o l u c n 1
e6
. g ( 0 . 1 6m o l )o l ' t i g l i ca c i d a
, n d1 0m l o i
conccntraltlcd
:S Oruasrefl uxed
i or l 8 hr nhi l esep ar at ing
wat er
i n a D c a n - S t u r kt r a p . T h c m i x t u r e r v a sc o o l e d ,c r t r a c t e d o n c e w i t h
1 0 0 m l o f w a t c r .d r i c d ( \ a : S O r ) . a n d c o n c e n t r a t e dT. h e r e s u l t i n g
o i l u a : d i s t i l l c dt h r o u g ha J 0 - c m h e a t e dH o l z m a n n c o l u m n g i v i n g
6 5 I g ( 9 - 1 o io, )i 2 - b u t l l t i g l a t ch a v i n gb p 6 6 o ( 8 T o r r ) . l i 1 . l 5[ p $ 1 . - s o
( 1 7 ' I o r r ) N \ { R ( ( ' D C l r ) : 6 ( T l V { S )6 . 8 2 ( m . l ) . 1 5 3 ( s c x t u n l c t ,
l . J . 6 t l t ) . l . l ( 5 ( s . b r o a d . 6 ) . l . . i l ( q . 2 . / . , . , 6H t ) . 0 , 9 0 ( d . , 1 .
J - . 6 [ ] z ) . 0 . 7 1 ( t . . 1 .J , 6 H t ) .
l l e t h o d B . r i ' T i g l r ca c i d ( 2 5 g . 0 l - : r n o l )a n d t h i o n l l c h l o r i d c( - i 7
g . 0 . l l l m t l l ) r r c r c h e a t c dI ' o r2 h r o n r r s t c a n tb a t h . [ . . r c c s tsh r t l n r ]
c h l o n d c \ \ r r \ r e n t o \ c db r c v a p o r a t i o na t r c d u c c dp r c s s u r c l.- b u t u n , r i
468 Inorganic Chemistry, Vol. 15, No. 2, 1976
(25 ml) wasadded,and the mixturewas heateduntil the evolution
of HCI ceased.The resultingoil wasdistilledto give35 g (89ozo)
of
6.
(4). Method A. 2-Butyl
2,3,4,5-Tetramethylcyclopent-2-enone
tiglate(l 5.6g, 0.1 mol) wasmagnetically
stirredwith I 50 g of a I :10
PzOs-methanesulfonic
acidmixture(prepared
by mechanically
stirring
i partof PzOsinto l0 partsof practical(95olo)
methanesulfonic
acid)l0
for 4 hr at room temperature.The deepred mixturewas added
dropwiseover 2 hr to 350 ml of water.and aqueousmaterialwas
with 300 ml of pentane.The pentanesolutionwaswashed
extracted
oncewith 100ml of saturatedaqueous
NaHCOI solutionand once
w i t h 1 0 0m l o f s a t u r a t e a
d q u e o uN
s a C l s o l u t i o nd, r i e d( N a z S O + ) ,
and concentrated.
Distillationgave7.6 g of 4 as a mixtureof isomers
h a v i n gb p 1 0 0 "( 3 0 T o r r ) ,l i t . l b p 5 9 . 8 ' ( 3 . 3T o r r ) ,w h i c hw a s9 2 o l o
pure by'glpc (50o/o
yield).
MethodB. A 2-t.flaskfittedwith a refluxcondenser,
a mechanical
stirrer,and a thermometer
waschargedwith 600 g oi PPA and 90
g ( 0 . 1 9m o l ) o f 2 - b u t y lt i g l a t e .T h e m i x t u r ew a sh e a r e dt o 9 0 o f o r
l0 minl7and thenquenched
by the carefuladditionoiice water. Its
final color was deep red. The hydrolyzedreactionmixture was
extracted
with pentane(l l.) and the pentane
solutionextracted
rvith
250 ml of I 1Vaqueous
NaOH solution.Fromthe aqueous
base.9.6
g of impuretiglicacidwasrecovered
by acidification,
extraction.
and
crystallization.
The pentanesolutionwasfurtherextractedwith rvltter.
s a t u r a t e ad q u e o uN
s a H C O I s o l u t i o na, n d s a t u r a t e ad q u e o u\sa C l
solutionD
. r y i n g( N a z S O + )c.o n c e n t r a t i oann, dd i s t i l l a t i ogna v c2 6
g o f m a t e r i ahl a v i n gb p 5 1 - , 5 8 '( 6 T o r r ) w h i c hr . r , a8sl o / o
4 by GLC
(260/0\.
Thismaterialwascontaminated
by'two highcrboilingfractions.
I t w a sn o t n e c e s s a rt yo r e m o v et h e s cc o n t a m i n a n t s .
1,2,3,4,5-Pentamethylcyclopentadiene
(l). To a solutionof 26 g
(0.15mol) of crude4 (irom theabovepreparation)
in 300mlof ether
maintained
at 0o in an icebathandmagnetically
stirredundernitrogen
w a sa d d e d1 2 0m l o f 2 . 2M m e t h y l l i t h i u (m0 . 2 8m o l )u s i n ga s y r i n g c .
T h e m i x t u r ew a ss t i r r e do v e r n i g h t .E x c e s m
s ethvllithium
w a sd e stro.n-b
e yd 'c a u t i o u sa d d i t i o no f 3 0 m l o i 3 - p r o p a n o lT. h e s o l u t r o n
w a sp o u r e di n t o w a t e ra n d e x t r a c t c d
u ' i t hc t h e r .a n d t h e c o m b i n c d
(ca.I00 mg) of iodine
organiclaversweretreatedwitha fewcrystals
.Is
W a t c rw a sa l l o w e dt o s e p a r a tfeo r 2 h i . T h e r e s u l t i n g " s o l u t w
i oans
washednith 0.1 ,t1NazSlO+solution(400ml) andsarurated
aqueous
N a C l s o l u t i o n( 1 5 0m l ) a n d d r i e d( N a : S O l ) . C o n c e n r r a t i o
an d
d i s t i l l a t i ogna v e1 5 . 6g ( 7 5 o zoof) I ( b p 5 1 " ( 7 T o r r ) .l i t . t b p 5 8 . 3 .
( 1 3 . -T5 o r r ) ) . \ M R I C D C I : ) : 6 2 . 5( m . t ) , 1 . 8 3( s ,b r o a d l. 5 ) .
(Method2\.1 e, mixtureof 20 g (0.1l2
Pentameth"v"lc.'-clopentadiene
m o l )o i i - a c e tly- 1 . 2 , 3 . 4 . 5 - p e n t a m e t h y l c y c l o p e n t la0dm
i eln(c0 . 63 6
, n d0 . 3 g o f p - t o l u e n c s u I f o n
m o l ) o f e t h ll e n eg l y c o l a
a icci dh y d r a r c
wasrefluredovernightwhileseparating
waterin a Dcan-Starktrap.
T h e m i x t u r er v a sc o o l e dc, x t r a c t e o
d n c ew i t h 1 0 0m l o f w a t c r .t u i c e
w i t h 1 0 0 - mp
l o r t i o n so f s a t u r a t e d
a q u e o uN
s a H C O : s o l u t i o na, n d
o n c ew i t h s a t u r a t e d
a q u c o u sN a C l s o l u t i o na, n d d r i e d( N a : S O + ) .
C--oncentration
at reducedprcssurcand distillationgavell g (T2orr)
oi 3. bp 17" (5 Torr).
3-Ethl-l-2,4,5-trimethylcy-clopent-2-en-l-one.
A mixrureof I kg
( 2 . 1m o l )o i l e a dd i o x i d ea n d 1 . 7L o i 3 - p e n t a n o n
wea sm c c h a n i c a l l l
stirredat reflur overnight.Yellowleadoxidcwasremovedbv filtration
and erccss-l-pentanone
and watcrwerercmovedb,t"distillation.The
residueu'astakenup in 1.5l. of methanoland stirrcdovernightwith
- sg o l ' K O H . T h e b a s ew a sn e u t r a l i z eud, i t h7 . 5m l o f c o n c c n t r a t e d
t-lCl.the mcthanolcvaporatcd
at reducedprcssurc,
and the rcsiduc
extracted
with equalvolumes
of water,I A' aqueous
NaOH solution.
s a t u r a t e ad q u e o uN
s a H C O : s o l u t i o na. n d s a t u r a t e ad q u e o uN
s aCl
s o l u t i o na n dd r i e d( N a : S O + ) .D i s t i l l a t i o g
n a v e8 7 g ( 3 8 " , ro, )l 8 . a s
a m i x t u r eo f i s o m e r sb.p 8 l - 8 4 " ( 6 T o r r ) . I r ( C C l + ) :1 6 9 4( C : O ) .
1 6 4 2( C : C ) c m l . T h i sc o m p o u n d
w a sn o t c h a r a c t c r i z ef u
drther
b u t u a s u s e dd i r e c t l , v .
Eth_v-ltetramethy
( 9). C.v-cl
lc.v-clopentadiene
openrcnone8 u,as dri ed
immediatellbeioreuseby passage
through40 g of crudc Woelnr
a l u m i n a( a c t i v i t yl ) . A 2 - 1 .r o u n d - b o t t o m ef dl a s k e q u i p p e df o r
magnetic
stirringand fittedu'itha precalibrated
addirionl'unnelcapped
uith a No-Air stoppcrwasflame-dried
andpurgedwith dr1,nirrogcn.
A f t c rc o o l i n g1, 7 4g ( l . l 5 m o l )o l ' f r e s h ldr r i e d8 a n d4 - s 0m l o f d r r
c t h c ru e r c l d d e dd i r c c t l rt o 1 f i gf l a s kr i r rc a n n u l lu n dr h c n7 _ 1m
5l
( l . l 5 m o l )o f 1 . 1M c t h e r e anlr c r h v l l i t h i u\m
\ , a sa d d e dr o t h c a d d i r i o n
funnel.againby cannula.Thc fleik wrrsimmersed
in an icebathand
t h em e t h y l l i t h i u m
a d d e ds l o w l lo ' c r 2 h r . T h e m i x t u r e* ' a sa l l o w c d
lo uarm to roomtemperaturc
andstirovcrnight.Exccss
mcthrllithiunr
* a s d e s t r o v cbdi t h ec a u t i o uas d d i t r o o
n f 2 - p r o p a n o l ( rn0r r )a n dt h e
Notes
etherealsolutionwasextractedwith water. To the etherlayerwas
a d d e d0 . 5g o f i o d i n e .O v e r0 . 5 h r l 8 m l o f w a t e rs e p a r a t e dT. h e
etherallayer was extractedtwice with 100-mlportionsof 0.1 M
NazSzO+
aqueous
solutionandtwicewith 100-mlportionsof saturated
NaCl solution.
dried(NazSO+).andconcentrated
to give 164.5g of
light yellowoil (95olo
crudeyield). Distillationgave130g (75olo)
of
9 ( E t M e a C p H )b p 5 9 - 6 1 o( 5 T o r r ) ,a s a m i x t u r eo f i s o m e r sT
. his
materialwasnot furthercharacterized
but useddirectlyin the following
I9
reactions.
(EtMeqCp)zFe.
Ferrouschloridewaspreparedby stirringat reflux
0 . 9 7g ( 6 m m o l )o f F e C l r . 0 . l 6 9g ( 3 m m o l )o f i r o n p o w d e r( e l e c trolyticallyreduced,300 mesh),and 20 ml of THF (distilledfrom
benzophenone
kety'l)for 5 hr underargon. A 0.052 M slurry of
E t M e + C p L iw a s p r e p a r e db y t h e a d d i t i o no f 1 5 0 m l o f 1 . 1 0M
methyllithium
t o a s o l u t i o no f 1 3 . 0g o f E t M e + C p Hi n 2 0 m l o f d r y
Et2O,evaporation
with THF. An aliquot
of ether,and replacement
of this slurry(42 ml) wasaddedto the ferrouschloridepreparation
via svringe.The reactionwasstirredovernight
at roomtemperature
with water.andextracted
with 200ml of CHCI:.
at reflux,quenched
Thc organiclayerwaswashedwith saturated
NaCl solution,
aqueous
d r i e d ( N a : S O + ) .a n d c o n c e n t r a t etdo g i v e 1 . 7 g ( 5 3 o l cor u d e )o f
( E t M e 4 C p ) : F eT. h r e er e c r y ' s t a l l i z a t ifor onm C H C I t - M e O H g a v e
(sealed
clearyellowcrystals(0 9 g), mp 14-5o
tube). NMR (CDCI:):
. . q( 1 . 6 /, = 7 . 6H z ) . M a s s
6 2 . 1 6( q . 2 . / = 7 . 6H z ) .I 7 0 ( s , 2 4 )O
( 7 0 e V ) : M + ' l . 3 5 - 1 .I r s p e c t r u m
( K B r .g r n t ) : 2 9 6 0 ,
spectrum
1 9 0 02. 8 6 0 1
. 1 7 01. 1 . s 01.4 2 01. 1 7 51. 0 2 - 5A. n a l . C a l c df o r C z z H l q F e :
C . 7 . 1 . 5 7t {:. 9 . 6 7 F o u n d ;C . 7 1 . 7 2 H
: . 9.73.
( E t \ ' t e , + C p ) : T i CTl :i.t a n i u mt r i c h l o r i d e
( l - s . 1g . 1 0 0m m o l )w a s
transfcrred
in a dribor into a dry, 1-1.three-necked
flaskfittedwith
No-Air stoppers
and equippedfor magneticstirring. The flaskwas
removedfrom thedry'box.I 75 ml oi dry TH F wasaddedvia a syringe,
the flaskwasflushedwith argon.and onestopperwasreplaced
with
a r c f l u xc o n d e n s c rA. s u s p e n s i oonf E t M e , r C p Liin T H F p r e p a r e d
asdcscribed
above(375ml. -100mmol) wasaddedvia syringeat room
t c m p c r a t u raen dt h c n t i x t u r cw a sr e f l u x e do v e r n i g h tA
. ftercooling
o l ' t h cm i r t u r ct o 0 o r n a n i c c b a t h .5 0 0m l o f l 2 r V H C I w a sa d d e d .
t h c r c s u l t i ndga r kr e ds o l u t r ow
n a sc x t r a c t ew
d i t h I l . o f C H C I : ,a n d
phasculs driedl\a:SO.r). Evaporation
theorganrc
gave25.5g (6lolo)
o f ( H t M e r C p ) :r1( ' ) : R e c r i s t a l l i z a t ifor no mC H C I ' I - M e O Hg a v c
l u s t r o upsu r p l e - b r o ucnr r s t a l sm. p 2 0 ( ) . - 5 - 2 0 1N"M
. R ( C D C I : ) :6
2 . 5 0( q ,1 . J = I 6 H z ) .1 . 0 -(l s .l 1 ) . 0 . 9 5( r . 6 ," / = 7 . 6H z ) . M a s s
s p e c t r u (m7 0 e V ) :\ ' l + . . 1 1 6I .r ( K B r . c m t ) : 2 9 6 0 , 2 9 0 0
1 ,4 5 01. 4 3 0 ,
1 3 9 0 ,1 3 8 0 1
. 3 6 5 .1 0 4 8 .1 0 2 0 .A n a l . C a l c df o r C : : H r + C l : T i :C .
6 3 . 3 2H
; . 8 l l : C l . 1 69 9 . F o u n d :C . 6 3 2 5 : H . 8 . 4 8 1
Cl. 17.25.
Acknowledgment. This research was supported by the
National Science Foundation (Grant GI 34284). We thank
Mr. Jim Demers for suggestingthe use of lead dioxide for the
preparationof 7, Mr. Lan K. Wong for his assistancein taking
the mass spectra under NIH Grant RR 00317 from the
Division of ResearchFacilities and Resources,and Dr. J. X.
McDermott for preparing l-acetyl-1,2,3,4,5-pentamethylcyclopentadiene. We also expressspecial thanks to Professor
R. F. Heck for his advice concerning our preparation of 6.
R e g i s t r yN o . T i g l i c a c i d .t l O - - s 9 -2l :- b u t a n o l7, 8 - 9 2 - 22; - b u t y l
tiglatc.281l7-58-4:2.3.4.5-tetramcthyl*'clopent-2-enone,
544,58-61-6r
l , 2 .3 . , 4 . , 5 - p emnet ath y ' l c v c l o p e n t a d i c4n0e4. - 5 - 4 4; - 7
m e t h yIli t h iu m ,
917-54-4:l-accnl- I .2,3.4,5-pcntamethl
lcyclopcntadiene,
I 5971-76-3:
3 - p e n t a n o n9e6. - 2 2 - 03: - e t h ly- 2 . 4 , , 5 - t r i m e t h y " l c l ' c l o p e nI t--o2n- e .n 5 7 4 5 9 - 4 0 - 2 te t h y l t e t r a m c t h y l c y c l o p e n t a d i e5 n7 e4 ,5 9 - 4 1 - l :
( E tM e + C p: )F e .5 7 4 73 - 9 8 - 0(;E tM e + C p: )T i C l : , , s 7 4 7 3 - 9l 9
.Referencesand Notes
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, r s a n o mC
e rh e n r . . 8 . 2(8179 6 7 ) .
( 2 ) . f. E . B c r c a sR. . t l . M a r r i c hL,. G . B c l ia. n dl l . l l . B r i n t z i n eJe.r,.4 r r t .
(hemS
. o r '9
. .. 1l.l l g ( 1 9 7 1 )
(-r)1.d
. c V r i c.sl . O r s .C h e m
. 2 5 .l 8 l S( 1 9 6 0 )
( 1 ) . 1E
. . B c r c a uP. hD T h c ' i sT. h cL . n i v c r s oi tfyM i c h i g a n
A,n nA r b o r .
\ 4i c h , .I 9 7 1
'I'.
( ) ) t l . R o h l .[ : . L a n g c . G o s s la. n d( i . R o t h . ^ l g r r e (r 'rh' .e m . I. n t . E d . E n s l . .
I , l l 7 t l 9 6 l ) : . 1 .\ \ ' . K a n ga n d P . l \ 1 M a i r l i s . 1 .O r g a n t t n t eCt .h e n r . .
: . H o s o k : r u al n d P . \ 4 M a i r l i s J. . . . 1 n tC. h e m .S o c . .
2 6 , 3 9 . 1( 1 9 7 1 ) T
(lq7l).
9 5 .1 9 2 , 1
( 6 ) R . t i . K i n g r n d A l r i r l t y . . 1 .. l t t t .( h e m . ^ S o c . . 9 4- ]. 7 7 3( 1 9 7 2 ) .
( 7 ) L B u r g c rA, . D e l a r a
, n d[ ' \ , l a z c n c 't,l e b . C h i m . . 4 t ' t u . 5 ]71, 0 6 ( 1 9 7 1 ) .
( S ) R . B K i n g .\ \ ' \ { . D o u g l l ' .a n d , . \ .I : i r l n , O r g . S v n t h .i,n p r e s sU
:.
B u r g c rr n d \ D el n . l / r , / i ( ' h i n r .. . 1 c t u . 5 6l.- l l 5 ( l q Tl )
( 9 ) . l \ l ( ' ' n i a . \ 1 . l _ l c r i r e r c n d . l l u l l . . \ rC
t .h i n rt.' r . 1 9 8 1 .2 9 9 1i l 9 7 0 ) .
Notes
InorganicChemistry,Vol. 15,No.z, 1976 469
(10) P.E. Eaton,
G. R. Carlson,
ad J. T. L€€,J. Or&Chen.n,407l (1973\.
,tt,
f;#',t;r!:i:-
(Maytt, tes3't,
talenrE76237
chen.Absn.s2.
(12) D. Seebach,
(1963).
Crez. ger.,96,2712
( I3) A. Schoenberc.
J. Bartoletti,andR. F- Heck,J.OE. Chem.,39,3318
(14) J. E. Bercaw,Privatecommunication.
(15) J. Munch-Peters€n,
J. Ory. Chen.,22,170(1957\.
(16) E. B. WomackandJ. Mcwhirter,"OrganicSynthescs",
Coll€ct.vol.
IU, Wiley,N€l' York, N.Y., p 714.
(17) Yieldsandpuriliesarehighlysusceptible
to variations
in t€mperature
and stirringefficiency.The reactionis exothermic
above80o,and
prefarations
ineflici€ntstirringin large-scxle
canl€adto veryhighintcmal
with reductionin yieldandconcomitant
tcmpcratures
lossof purity.
(lE) A fex,nllpsof 6.lVHCI r{ill alsosufficeard mayrosultin a cleaner
( I 9) Thematerialisoblain€dasa mi{tureof isomers.
pu.ification
andextensive
doesrtotsimplifylhespertrum.Prominant
NMR resonaler(CDCI])
areobrrv€dat 6 2.45(q,2. J = 7 Hz), 1.80(s, 12.broad),0.98(t, 3,
J=1Hz\.