Synthesis of five-and six-membered 1,3,3-trimethyl-2-(trimethylsilyl) cycloalkenes: A novel preparation of alkyl/alkenyl/aryl 2,5,5-trimethyl-1- cyclopentenyl ketones

Article abstract of DOI:10.2298/JSC120501015A

1,3,3-trimethyl-2-(trimethylsilyl)cyclopentene and 1,3,3-trimethyl-2- -(trimethylsilyl)cyclohexene were prepared in good yields by the Wurtz-Fittig coupling reaction of the corresponding 2-iodo-1,3,3-trimethylcyclopentene and 2-chloro-1,3,3-trimethylcyclohexene with metallic sodium and chlorotrimethylsilane in anhydrous ether solvent. The Friedel-Crafts acylation reaction of 1,3,3-trimethyl-2-(trimethylsilyl)cyclopentene with six different acid chlorides and the novel preparation of six alkyl/alkenyl/aryl 2,5,5-trimethyl-1-cyclopentenyl ketones are reported.

Full text of DOI:10.2298/JSC120501015A

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J. Serb. Chem. Soc. 78 (0) 1–18 (2013)
JSCS–5374
UDC
Original scientific paper
Synthesis of five- and six-membered 2-trimethylsilyl-1,3,3-
-trimethylcycloalkenes: a novel preparation of
alkyl/alkenyl/aryl-(1′,3′,3′-trimethylcyclopentenyl)ketones
*
VENKATESHA M. ACHANNA and HARIPRASAD SURESH
Department of Chemistry, Central College Campus, Palace Road, Bangalore University,
Bangalore – 560001, India
(Received 1 May, revised 1 December 2012)
Abstract: 2-Trimethylsilyl-1,3,3-trimethylcyclopentene and 2-trimethylsilyl-
1,3,3-trimethylcyclohexene were prepared in good yields by the Wurtz–Fittig
coupling reaction of the corresponding 2-iodo-1,3,3-trimethylcyclopentene and
2-chloro-1,3,3-trimethylcyclohexene
with
metallic
sodium
and
chlorotrimethylsilane in anhydrous ether solvent. The Friedel–Crafts acylation
reaction of 2-trimethylsilyl-1,3,3-trimethylcyclopentene with six different acid
chlorides and the novel preparation of six alkyl/alkenyl/aryl-(1′,3′,3′-
trimethylcyclopentenyl)ketones is reported.
Keywords: cyclic vinylsilanes; anionic synthons; Wurtz–Fittig reaction;
Friedel–Crafts acylation; β-silyl effect.
INTRODUCTION
Cyclic vinylsilanes are an important class of compounds in synthetic organic
chemistry.1 The compounds are anionic synthons with the trimethylsilyl– group
behaving as a masking agent.2 The silicon in these compounds is capable of
directing a reaction in a highly regio- and stereo-specific manner. Several
methods have been reported in the literature for the preparation of cyclic
vinylsilanes.3
Our laboratory is primarily involved in preparation of cyclic vinylsilanes by
employing the Wurtz–Fittig type coupling reaction of cyclic vinyl halides with
sodium and chlorotrimethylsilane in suitable anhydrous solvent. The method is
simple, and employing this reaction we have been successful in preparing a
number of simple and substituted cyclic vinyl silanes. Various novel reactions of
the prepared simple and substituted cyclic vinylsilanes discovered in our
laboratory have also been reported.4
*Corresponding author. E-mail: hariprasad@bub.ernet.in
doi: 10.2298/JSC120501015A
1

2
ACHANNA and SURESH
In further studies and in attempts to prepare some important substituted
cyclic vinylsilanes, we chose to synthesize 2-trimethylsilyl-1,3,3-
trimethylcyclopentene (1) and 2-trimethylsilyl-1,3,3-trimethylcyclohexene (2).
The compounds 1 and 2 would serve as potential synthons to several terpenes,
the Vitamin-A and related group of compounds.5 In particular, it may be noted
that the 1,3,3-trimethylcycloalkanyl- group is a common functionality present in
the capnellane,6a taiwaniaquinoid,6b actinidiolide,6c heydechenone,6d and labdane
diterpene6e group of compounds. Paquette has reported the preparation of 1 by
the tosyl hydrazone route, and isolation using preparative VPC.7 To our
knowledge, the compound 2 has not been reported, but its corresponding vinyl
stannane has been synthesized.8
In this article we wish to report the successful preparation of 1 and 2 by
Wurtz–Fittig coupling reaction. The Friedel–Crafts acylation of 1 with six
different acid chlorides gave some novel alkyl/alkenyl/aryl-(1′,3′,3′-
trimethylcyclopentenyl)ketones.
RESULTS AND DISCUSSION
Chemistry
Preparation of five- and six-membered α,α,α′-trimethylcycloalkanones. We
are hereby reporting
a
new route for the synthesis of α,α,α′-
trimethylcyclopentanone.9a Diethyl adipate (3) upon Dieckmann cyclisation with
sodium/toluene afforded 2-carbethoxycyclopentanone (4).9b Total methylation of
4 using methyl iodide (6 equivalents) and sodium hydride (4 equivalents), gave
2-carbethoxy-2,5,5-trimethylcyclopentanone (5) in 71% yield. Subsequent
hydrochloric acid catalyzed hydrolysis and decarboxylation gave the pure five-
membered 2,2,5-trimethylcyclopentanone (6) in 58% isolated yield from 5.
The α,α,α′-trimethylcyclohexanone was prepared according to reported
literature procedure.10 Reaction of cyclohexanone (7) with diethyl oxalate in
presence of sodium ethoxide followed by pyrolysis with a catalytic amount of
ground iron powder/glass-wool at 175 oC gave 2-carbethoxycyclohexanone (8) in
45% yield. Total methylation of 8 using 4 equivalents of sodium hydride and 6
equivalents of methyl iodide gave 2-carbethoxy-2,6,6-trimethylcyclohexanone
(9) in 78% yield. Hydrochloric acid catalyzed hydrolysis and decarboxylation
yielded pure 2,2,6-trimethylcyclohexanone (10) in 77% yield (Scheme 1).
Conversion to cyclic vinyl halides. A number of procedures have been
developed for the conversion of ketones to vinyl halides. This is due to the
growing use of metal catalyzed coupling reactions of alky/alkenyl/aryl halides in
organic synthesis. Some of the recently developed reagents used to perform the
transformation include (PhO)3P/X2,11a CH3COX/CF3COOH,11b WCl6,11c
(EtO)2P(O)Cl/P(Ph3)/X2,11d along with the traditional halogenating agents such
as thionyl chloride and phosphorous pentachloride.11e-g

SYNTHESIS TRIMETHYLCYCLOALKENES
3
We explored some of the reagents reported for the conversion of cyclic
ketones to cycloalkenyl halides. Our investigations have shown Takeda’s
general method for preparation of gem-halides most useful.12
The method
involves the conversion of the carbonyl compounds to their corresponding
hydrazones, followed by reaction with cupric halide/Et3N.
The compounds 6 and 10 were converted to their corresponding hydrazones
2,2,5-trimethylcyclopentanone hydrazone (11) in 75% yield and 2,2,6-
trimethylcyclohexanone hydrazone (12)6d in 78% yield.
Treatment of the hydrazones 11 and 12 with 6 equivalents of copper (II)
chloride and
3
equivalents of triethylamine gave 1,1-dichloro-2,2,5-
trimethylcyclopentane (13) in 33% yield and 1,1-dichloro-2,2,6-
trimethylcyclohexane (14) in 42% yield respectively. Subsequent
dehydrochlorination of 13 and 14 employing morpholine/DMSO and benzene13
gave 2-chloro-1,3,3-trimethylcyclopentene (17) in 31% yield and 2-chloro-1,3,3-
trimethylcyclohexene (18)5c in 40% yield respectively.
Similar bromination of 11/12 with 6 equivalents of copper (II) bromide and
3 equivalents of triethylamine gave a mixture of gem-dibromides 15/16 and vinyl
bromides 19/20 in 1:1 ratio due to the elimination of HBr under the reaction
conditions employed. Without isolating the mixture of gem-dibromide and vinyl
bromide, the mixture was subjected to dehydrobromination using
morpholine/DMSO/benzene to isolate 2-bromo-1,3,3-trimethylcyclopentene (19)
in 64% yield and 2-bromo-1,3,3-trimethylcyclohexene (20) in 69% yield.
The cyclic vinyl iodides 2-iodo-1,3,3-trimethylcyclopentene (21) and 2-
iodo-1,3,3-trimethylcyclohexene (22)6d were prepared by adopting Barton’s vinyl
iodination procedure. Reaction of 11 and 12 with iodine and DBN6d,14 gave 21 in
79% yield and 22 in 82% yield. (Scheme 2). The results for the preparation of
the cyclic vinyl halides 17-22 are summarized in Table I.
Wurtz–Fittig coupling reaction to the five- and six-membered 2-trimethylsilyl-
1,3,3-trimethylcycloalkenes
The cyclic vinyl halides 17-22 were subjected to the Wurtz–Fittig coupling
reaction with sodium and chlorotrimethylsilane in anhydrous ether solvent, using
protocols well established in our laboratory.4 The reactions were followed using
gas chromatography. After completion of reaction, as indicated by the
chromatograms of aliquot samples, the mixtures were worked up and distilled to
isolate pure 1 and 2 (Scheme 3).
Each reaction was carried out a minimum of five times for each cyclic vinyl
halide substrate (17-22) and the yields of the products 1/2 are averaged and
shown in Table II.
The hindered cyclic vinyl halides 17-22 showed difference in reactivity with
sodium metal in the Wurtz–Fittig reaction. The five membered cyclic vinyl

4
ACHANNA and SURESH
halides
2-chloro-1,3,3-trimethylcyclopentene
(17),
2-bromo-1,3,3-
trimethylcyclopentene (19) and 2-iodo-1,3,3-trimethylcyclopentene (21) reacted
with sodium smoothly to form 1 in > 70% yields (Table II). Among all the five-
membered cyclic vinyl halides, the 2-iodo-1,3,3-trimethylcyclopentene (21) was
found to be the best substrate for the preparation of 2-trimethylsilyl-1,3,3-
trimethylcyclopentene (1), with the highest isolated yield of 81-83%.
In case of the six-membered ring system, the 2-chloro-1,3,3-
trimethylcyclohexene (18)5c was found to be the best substrate with isolated
yields of 2-trimethylsilyl-1,3,3-trimethylcyclohexene (2) in the range of 75-77%
(Table II). The other six-membered cyclic vinyl halides 20 and 22 did not give
satisfactory yields, under our reaction conditions. Change of metal to potassium,
magnesium or lithium and use of solvents: THF, benzene or HMPA gave 2 in
less than 10% yields.
We were not able to prepare 2 in large quantities (1 g scale). Although the
vinyl halides 20 and 22 could be prepared in large quantities, their Wurtz–Fittig
couplings proceeded in low and inconsistent yields. On the other hand, although
the Wurtz–Fittig reaction of the vinyl chloride 18 took place in good yields, the
preparation of 18 proved difficult because of low yields5c in both gem-
chlorination (42% yield) and dehydrochlorination steps (40% yield).
In the light of preparation of the five-membered cyclic vinylsilane 1 in
sufficient quantities (2 g scale), the Friedel–Crafts acylation reactions of the five
membered cyclic vinyl silane 1 with six different acid chlorides were carried out.
Conversion to Novel Alkyl/alkenyl/aryl-(1′,3′,3′-trimethylcyclopentenyl)
ketones. The Friedel–Crafts acylation reactions are some of the most widely
studied and used reactions in organosilicon chemistry.1-3 The reaction has been
extended to several classes of organosilicon compounds like allylsilanes,
arylsilanes, vinylsilanes etc. to obtain a wide variety of carbonyl moiety
containing products. The conversions employ the β-silyl effect.15 Using the
Friedel–Crafts acylation reaction and employing standardized procedures, our
laboratory had earlier reported the synthesis of a wide variety of novel products
from cyclic vinylsilanes.4
The Friedel–Crafts reaction of 1 was carried out in 0.2 g scales with 3 molar
equivalents each of anhydrous aluminium chloride and six different acid
chlorides in dichloromethane solvent.
The reactions were found to be clean and afforded the novel
alkyl/alkenyl/aryl-(1′,3′,3′-trimethylcyclopentenyl) ketones 23 a-f (Scheme 4) in
isolated yields ranging between 65-87 % in five trials for each substrate (Table
III).
The compound 23 a is a known compound prepared earlier by Stille by the
palladium catalysed coupling of (α-ethoxyvinyl)trimethylstannane with 1-
trifluoromethanesulphonyl-1,3,3-trimethylcyclopentene.16 All the other (1′,3′,3′-

SYNTHESIS TRIMETHYLCYCLOALKENES
5
trimethylcyclopentenyl)ketones 23 b-f are not reported in the literature, and are
being reported by us for the first time. Our procedure employs the Friedel–Crafts
acylation reaction of 1 and utilizes the β-silyl effect. The compound 23 c is the
lower analogue of the naturally occurring β-damascone.17 The compounds 23 a-f
maybe useful in the aroma and perfume industries.18
EXPERIMENTAL
All reactions were monitored using GC or TLC. TLC were run on Merck TLC Silica-gel
o
60 F254 pre-coated plates with elution solvent 1:20 ethyl acetate/hexane (60-80 C fraction).
GC was run on SE-30 SS 2m x 1/8” column Mayura 9800 Gas Chromatograph. IR spectra
were recorded on Shimadzu FT-IR 8400S on NaCl flats as neat thin liquid film samples.
NMR spectra were recorded in CDCl3 with a Bruker AMX 400 spectrometer using
tetramethylsilane (TMS) as an internal standard. GC-MS spectra were obtained using a
Shimadzu GC-MS QP 5050A instrument equipped with a 30 m x 0.32 mm BP-5 capillary
column. Elemental Analysis were obtained using Elementar Vario Microcube-15106062
instrument. All yields refer to the isolated yields of the products.
General procedure for the synthesis of five- and six-membered 2-chloro/bromo-1,3,3-
trimethylcycloalkenes (17-20)
To a solution of copper (II) halide (6 molar equivalents) in 80 mL methanol was added
triethylamine (3 molar equivalents) at 20 οC. The reaction mixture was stirred for 10 minutes
and cooled to 0 οC. A methanolic solution of α,α,α′-trimethylcycloalkanone hydrazone 11/12
(3 g in 30 mL MeOH) was added drop wise over 20 minutes, and the mixture further stirred
for 2 hours, simultaneously allowing the reaction mixture to attain ambient temperature. TLC
indicated complete conversion of the hydrazone. The mixture was quenched by adding 50
mL of 3.5% aqueous NH3 solution, and extracted with ether (3 x 30 mL). The combined
organic extracts were washed with saturated NaHCO3 (2 x 30 mL), water (2 x 30 mL),
saturated NaCl (2 x 30 mL) and dried (anhydrous MgSO4). The solvent was removed on a
rotavapor and the residue distilled under reduced pressure to isolate the halogenated products.
The mixture of halogenated products (2 g) was added to morpholine (10 molar
equivalents)/DMSO (10 molar equivalents)/8 mL of benzene and refluxed at 100 °C for 24
hours. Gas chromatograms indicated complete conversion to the cyclic vinyl halides 17-20.
The mixture was cooled, added to ice cold 2N HCl (50 mL) and extracted with ether (3 x 40
mL). The combined organic extracts were washed with saturated NaHCO3 (2 x 30 mL), water
(2 x 30 mL), saturated NaCl (2 x 30 mL) and dried (an. MgSO4). The solvent was removed
on a rotavapor and the residue distilled under reduced pressure to isolate the pure 2-
chloro/bromo-1,3,3-trimethylcycloalkenes (17-20).
General procedure for the synthesis of five- and six-membered 2-iodo-1,3,3-
trimethylcycloalkenes (21/22):
To a suspension of 4 g of α,α,α′-trimethylcycloalkanone hydrazone 11/12 and 6 molar
equivalents of 1,5–diazabicyclo[4.3.0]non-5-ene in 50 mL anhydrous ether was added
dropwise a solution of 2.2 molar equivalents iodine in 100 mL anhydrous ether. The
reaction mixture was stirred for 3.5 hours, when the GC indicated completion of reaction. The
reaction mixture was washed with saturated sodium bicarbonate solution (20 mL). The
ethereal layer was separated and the aqueous layer re-extracted with ether (3 x 40 mL). The
organic layers were combined, dried over anhydrous sodium sulfate, and evaporated in-vacuo.

6
ACHANNA and SURESH
The residue was chromatographed through silica gel using hexane as the solvent to afford the
cyclic vinyl iodides 21/22.
General procedure for the synthesis of 2-trimethylsilyl-1,3,3-trimethylcycloalkenes (1/2):
To a suspension of finely cut sodium pieces (5 molar equivalents) and
chlorotrimethylsilane (3 molar equivalents) in 10 mL of dry ether was added 2-halo-1,3,3-
trimethylcycloalkene [3.2g (13.5 mmol) of 21; or 0.22g (1.3 mmol) of 18] in 10 mL of
anhydrous ether. The mixture was refluxed with efficient stirring on an oil bath at 45 – 50 °C,
when a deep navy-blue coloration developed. Monitoring the reaction by GC indicated that
the reactants required 6 hours for complete conversion to products. The mixture was cooled;
the precipitated solids and remaining sodium were removed by filtering on a plug of glass
wool and washed with ether (2 x 5 mL). Saturated sodium bicarbonate (15 mL) was added to
the combined filtrate, the layers were separated, and the organic layer was successively
washed with water (3 x 10 mL), saturated sodium chloride (15 mL), dried (anhydrous
Na2CO3), concentrated and distilled under reduce pressure to isolate 1 and 2. The yields of
isolated products are given in Table II.
General procedure for the synthesis of alkyl/alkenyl/aryl-(1′,3′,3′-
trimethylcyclopentenyl)ketones (23 a-f):
To a magnetically stirred mixture of anhydrous AlCl3 (3 molar equivalents) and acid
chloride (3 molar equivalents) in dry CH2Cl2 (20 mL), cooled to – 15 °C on an ice- salt bath,
was added 0.2 g of 1 in 5 ml of dry CH2Cl2 drop wise over a period of 5 minutes. After three
hours of stirring, the gas chromatogram of aliquot indicated complete disappearance of the
reactant 1. Saturated NaHCO3 solution (20 mL) was added to the mixture and stirred for 30
minutes, simultaneously allowing the reaction to attain room temperature. The organic layer
was separated, washed with NaHCO3 solution (2 x 20 mL), water (25 mL) and saturated NaCl
solution (20 mL). The pale yellow organic extract was dried (anhydrous Na2SO4) concentrated
and finally subjected to bulb to bulb distillation under reduced pressure to isolate individually
the alkyl/alkenyl/aryl-(1′,3′,3′-trimethylcyclopentenyl)ketones (23 a-f).
CONCLUSIONS
The simple synthesis of 2-trimethylsilyl-1,3,3-trimethylcyclopentene and 2-
trimethylsilyl-1,3,3-trimethylcyclohexene is reported. The Friedel–Crafts
acylations of 2-trimethylsilyl-1,3,3-trimethylcyclopentene gave a series of six
alkyl/alkenyl/aryl-(1′,3′,3′-trimethylcyclopentenyl)ketones.
SUPPLEMENTARY DATA
The spectral characterization data is available as supplementary material.
Acknowledgment. Grateful thanks are due to the Bangalore University Internal Research
Fund; University Grants Commission and Department of Science and Technology,
Government of India, New Delhi for financial assistance. MAV thanks the Council for
Scientific and Industrial Research for a Research Fellowship. We are also thankful to the
NMR Department, Indian Institute of Science – Bangalore.

SYNTHESIS TRIMETHYLCYCLOALKENES
7
И З В О Д
СИНТЕЗА ПЕТО- И ШЕСТОЧЛАНИХ ПРСТЕНОВА ДЕРИВАТА 2-ТРИМЕТИЛСИЛИЛ-
1,3,3-ТРИМЕТИЛЦИКЛОАЛКАНА: НОВ ПОСТУПАК СИНТЕЗЕ
АЛКИЛ/АЛКЕНИЛ/АРИЛ-(1′,3′,3′-ТРИМЕТИЛЦИКЛОПЕНТЕНИЛ)КЕТОНА
VENKATESHA M. ACHANNA и HARIPRASAD SURESH
Department of Chemistry, Central College Campus, Palace Road, Bangalore University,
Bangalore – 560001, India
2-триметилсилил-1,3,3-триметилциклопентан
триметилциклохексан добијени су, у добром приносу, Вурц-Фитиг-овим купловањем
полазећи од одговарајућих 2-јод-1,3,3-триметилциклопентена 2-хлор-1,3,3-
триметилцикохексена са металним натријумом хлортриметилсиланом
и
2-триметилсилил-1,3,3-
и
и
у
анхидрованом етру као растварачу. Приказано је Фридел-Крафцовим ациловање 2-
триметилсилил-1,3,3-триметилциклопентена са шест различитих алканоилхлорида и
нова синтеза шест алкил/алкенил/арил-(1′,3′,3′-триметилциклопентенил)кетона.
(Примљено 1. маја, ревидирано 1. децембра 2012)
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SYNTHESIS TRIMETHYLCYCLOALKENES
9
Captions for Tables
TABLE I: Synthesis of five- and six-membered 2-halo-1,3,3-
trimethylcycloalkenes 17-22
TABLE II: Synthesis of 2-trimethylsilyl-1,3,3-trimethylcycloalkenes 1 and
2 by Wurtz-Fittig coupling of 17-22 with sodium and chlorotrimethylsilane in
anhydrous ether solvent
TABLE III: Synthesis
of
some
novel
alkyl/alkenyl/aryl-(1',3',3'-
trimethylcyclopentenyl)
ketones 23 a-f
TABLE I: Synthesis of five- and six-membered 2-halo-1,3,3-
trimethylcycloalkenes 17-22
Entr
Substr
Reagent/Base/So
lvent
Rin
g size
Prod
Yiel
d (%)
y
ate
uct
17
31
40
64
69
1
2
3
4
11
CuCl2/Et3N/MeO
CuCl2/Et3N/MeO
CuBr2/Et3N/MeO
CuBr2/Et3N/MeO
5
6
5
6
H
H
H
H
18
12
19
11
20
12
5
6
11
I2/DBN/Et2O
I2/DBN/Et2O
5
6
21
79
82
126d
226d

10
ACHANNA and SURESH
TABLE II: Synthesis of 2-trimethylsilyl-1,3,3-trimethylcycloalkenes 1 and
2 by Wurtz-Fittig coupling of 17-22 with sodium and chlorotrimethylsilane in
anhydrous ether solvent
Entry
Substra
Haloge
Ring
Produc
Yield
te
n
size
t
(%)
1
2
1
2
1
2
73–76
75–77
72–74
<10
81–83
<10
1
2
3
4
5
6
17
Cl
Cl
Br
Br
I
5
6
5
6
5
6
185c
19
20
21
226d
I
TABLE III: Synthesis of some novel alkyl/alkenyl/aryl-(1',3',3'-
trimethylcyclopentenyl)ketones 23 a-f
o
Entry
Product
R
Yield
b.p. C /
(%)
1mm
1
2
3
4
5
6
23 a16
23 b
23 c
23 d
23 e
23 f
-CH3
-C2H5
-(E)-C3H5
n-C4H9
n-C5H11
-C6H5
65
71
78
83
87
86
53–57
64–67
69–73
68–72
71–74
82–84

SYNTHESIS TRIMETHYLCYCLOALKENES
11
Scheme 1: Synthesis of five- and six-membered α, α, α′-trimethylcycloalkanones
(6/10)
Scheme 2: Synthesis of five- and six-membered 2-halo-1,3,3-
trimethylcycloalkenes (17-22)
Scheme
3:
Wurtz–Fittig
coupling
to
2-trimethylsilyl-1,3,3-
trimethylcycloalkenes (1/2)
Scheme 4: Facile route for the synthesis of alkyl/alkenyl/aryl-(1',3',3'-
trimethylcycloalkenyl)ketones (23a–f)
O
O
O
C O O E t
H +
H 2
C O O E t
C O O E t
C O O E t
N a
N aH / M e I
T H F
T o lu e n e
O
4
3
5
6
O
O
O
N aO C 2 H 5
(C O O C 2 H 5
/
O
C O O E t
C O O E t
H +
H 2
N a H / M e I
T H F
)
2
O
F e /g lass w o o l
1 7 0 o C
7
8
1 0
9
S ch em e 1 : S y n th e sis o f fiv e- an d six -m em b e re d    '-trim eth y lc y clo a lk an o n e s (6 /1 0 )
O
N N H 2
X
X
X
N H 2 N H 2
C u X 2
E t3
M o rp h o lin e
( )
E t3
N /
n
( )
n
N
/
D M S O
/
( )
n
( )
n
C 2 H 5 O H
B en z en e
M e O H
1 7 : n = 1 , X = C l
1 8 : n = 2 , X = C l
1 9 : n = 1 , X = B r
2 0 : n = 2 , X = B r
1 3 : n = 1 , X = C l
1 4 : n = 2 , X = C l
1 5 : n = 1 , X = B r
1 6 : n = 2 , X = B r
6 : n = 1
1 0 : n = 2
1 1 : n = 1
1 2 : n = 2
2 1 : n = 1 , X = I
2 2 : n = 2 , X = I
I2 /D B N , E t2
O
S c h e m e 2 : S y n th e sis o f fiv e- an d six -m em b e re d 2 -h a lo -1 ,3 ,3 -trim e th y lc y c lo a lk e n es (1 7 -2 2 )

12
ACHANNA and SURESH
X
S iM e 3
N a / C l-S iM e 3
E t2 O , 4 5 - 5 0 o C
(
)
(
)
n
n
1 : n = 1
2 : n = 2
1 7 : n = 1 , X = C l; 1 9 : n = 1 , X = B r; 2 1 : n = 1 , X = I
1 8 : n = 2 , X = C l; 2 0 : n = 2 , X = B r; 2 2 : n = 2 , X = I
S c h e m e 3 : W u rtz -F ittig c o u p lin g to 2 -trim e th y lsily l-1 ,3 ,3 -trim e th y lcy c lo alk e n e s (1 /2 ).
O
S iM e3
an . A lC l3 / C H 2 C l2
R
R C O C l
+
-1 5 to 0 o C
2 3 a -f
1
(a) R : -C H 3 (b ) R : -C H 2 C H 3 (c ) R : tra n s-C H = C H -C H 3 (d ) R : n -C 4 H 9 (e ) R : n -C 5 H 1 1 (f) R : -C 6 H 5
S c h e m e 4 : F a cile ro u te fo r th e sy n th e sis o f alk y l/a lk en y l/a ry l-(1 ',3 ',3 '-trim eth y lc y clo p e n ten y l)k eto n e s (2 3 a -f)

SYNTHESIS TRIMETHYLCYCLOALKENES
13
SUPPLEMENTARY MATERIAL
SPECTRAL DATA OF THE PRODUCTS
2-Trimethylsilyl-1,3,3-trimethylcyclopentene (1).7 Yield: 81-83 %; light
yellow oil; b. p. 65–70 °C/4 mm. IR (film, cm-1): 2958, 2866, 1647, 1458, 1377,
1261, 1095, 1016, 802. GC-MS: m/z (relative intensity): 182 (13, M+), 167 (72),
108 (28), 93 (25), 73 (100%, base peak), 74 (46), 59 (58), 45 (62). 1H-NMR (400
MHz, CDCl3, δ / ppm): 0.08 (9H, s), 0.98 (6H, s), 1.48 – 1.51 (2H, t, J = 7.2
Hz), 1.70 (3H, s), 2.17 – 2.21 (2H, t, J = 7.2). 13C-NMR (100, MHz, CDCl3, δ /
ppm): 1.5, 17.9, 28.7, 28.8, 39.0, 41.8, 51.7, 142.7, 149.6.
2-Trimethylsilyl-1,3,3-trimethylcyclohexene (2). New compound. Yield: 75-
77 %; light yellow oil; b. p. 77–80 °C/2 mm. Anal. Calcd. for C12H24Si: C, 73.38;
H, 12.32 Found: C, 73.58; H, 12.42 %. IR (film, cm-1): 2950, 2866, 1649, 1581,
1452, 1456, 1255, 1095, 1051, 840, 808, 761. GC-MS: m/z (relative intensity):
196 (3, M+), 181(8), 123 (10), 122 (31), 107 (25), 73 (100%, base peak), 59 (15),
45 (24), 43 (15). 1H-NMR (400 MHz, CDCl3, δ / ppm): 0.22 (9H, s), 1.05 (6H,
s), 1.33 – 1.36 (2H, m), 1.53 – 1.59 (2H, m), 1.75 (3H, s), 1.90 – 1.94 (2H, t, J =
8Hz ). 13C-NMR (100, MHz, CDCl3, δ / ppm): 3.8, 19.3, 24.7, 29.5, 34.6, 35.5,
41.3, 139.1, 142.8.
2,2,5-Trimethylcyclopentanone hydrazone (11). New compound. Yield: 75
%; white needles. Anal. Calcd. for C8H16N2: C, 68.52; H, 11.5; N, 19.98%.
Found: C, 68.34; H, 11.65; N, 20.3 %. IR (film, cm-1): 3357, 3211, 2962, 2871,
1737, 1461, 1380, 1361, 1255, 1080, 1006. GC-MS: m/z (relative intensity):140
(35, M+), 125 (46), 124 (54), 109 (10), 108 (17), 95 (21), 81 (26), 69 (28), 67
1
(29), 55 (63), 41 (100%, base peak). H-NMR (400 MHz, CDCl3, δ / ppm): 1.07
(3H, s), 1.13 (3H, s), 1.16 – 1.18 (3H, d, J = 8), 1.46 – 1.56 (2H, m), 1.68 – 1.75
(1H, m), 1.93 – 2.00 (1H, m), 2.76 – 2.81 (1H, m), 4.8 (2H, s). 13C-NMR (100,
MHz, CDCl3, δ / ppm): 15.9, 27.2, 27.6, 30.2, 32.8, 38.2, 42.1, 168.6.
*Corresponding author; Email: hariprasad@bub.ernet.in
;
Tel:
+
918022961351
2,2,6-Trimethylcyclohexanone hydrazone (12).6d Yield: 78%; White needles.
GC-MS: m/z (relative intensity):154 (5, M+), 139 (3), 122 (5), 109 (4), 95 (5), 81
1
(10), 67 (14), 56 (31), 41 (100%, base peak). H-NMR (400 MHz, CDCl3, δ /
ppm): 1.12 (6H, s), 1.16 (3H, d, J = 8), 1.53 – 1.58(2H, m), 1.59 – 1.63 (2H, m),
`1.72-1.77(2H, m), 2.95-2.99 (1H, m), 4.69 (2H, s). 13C-NMR (100, MHz, CDCl3,
δ / ppm): 17.6, 17.8, 26.9, 29.3, 29.9, 32.1, 38.06, 40.8, 163.02.
1,1-Dichloro-2,2,5-trimethylcyclopentane (13). New compound. Yield: 33
%; Yellow oil; b. p. 60-63 °C/4mm. Anal. Calcd for C8H14Cl2: C, 53.06; H, 7.79
%. Found: C, 53.47; H, 7.29 %. IR (film, cm-1): 2966, 2939, 2875, 1506, 1455,
1371, 1217, 1105, 1002, 973, 914, 848, 784, and 761. GC-MS: m/z (relative
intensity): 184 (1, M+4), 182 (3, M+2), 180 (1, M+), 144 (1), 131 (2), 129 (7),

14
ACHANNA and SURESH
109 (29), 104 (16), 97 (22), 77 (9), 70 (23), 69 (100%, base peak), 56 (19), 55
1
(9), 42 (14), 41 (30). H-NMR (400 MHz, CDCl3, δ / ppm): 1.17 (3H, s), 1.22-
1.24 (3H, d, J = 8 Hz), 1.27 (3H, s), 1.36-1.43 (1H, m), 1.55-1.62 (1H, m), 1.73-
1.78 (1H, m), 1.81-1.93 (1H, m), 2.65-2.71 (1H, m). 13C-NMR (100, MHz,
CDCl3, δ / ppm): 15.0, 24.0, 27.0, 27.3, 35.0, 46.8, 50.5, 106.9.
1,1-Dichloro-2,2,6-trimethylcyclohexane (14). New compound. Yield: 42
%; Yellow oil; b. p. 72-75 °C /4mm. Anal. Calcd for C9H16Cl2: C, 55.40; H, 8.26
%. Found: C, 55.12; H, 8.45 %. IR (film, cm-1): 2987, 2937, 2864, 1456, 1373,
1326, 1278, 1242, 1215, 1175, 1122, 1058, 989. GC-MS: m/z (relative
intensity): 198 (1, M+4), 196 (3 M+2), 194 (1, M+), 145 (4), 143 (2), 123 (20),
109 (6), 107 (21), 93 (6), 91 (16), 81 (32), 69 (34), 53 (39), 41 (100, base peak).
1H-NMR (400 MHz, CDCl3, δ / ppm): 1.21-1.23 (3H, d, J = 8 Hz), 1.24 (3H, s),
1.28 (3H, s), 1.36 – 1.41 (1H, m), 1.46 – 1.61 (4H, m), 1.82 – 1.85 (1H, m), 2.36
– 2.37 (1H, m) 13C-NMR (100, MHz, CDCl3, δ / ppm): 18.0, 20.6, 24.8, 27.3,
32.0, 36.5, 42.6, 44.8, 108.6.
2-Chloro-1,3,3-trimethylcyclopentene (17). New compound. Yield: 31 %;
Yellow oil; b.p. 60-63 °C/4mm. Anal. Calcd for C8H13Cl: C, 66.43; H, 9.06 %.
Found: C, 66.23; H, 9.27 %. IR (film, cm-1): 2960, 2867, 1664, 1461, 1363, 1259,
1006, 939. GC-MS: m/z (relative intensity): 146 (5, M+2), 144 (17, M+), 131
(31), 129 (100%, base peak), 93 (59), 91 (31), 78 (43), 63 (67), 53 (14), 45 (30),
1
41 (22). H-NMR (400 MHz, CDCl3, δ / ppm): 1.04 (6H, s), 1.69 (3H, s), 1.76
(3H, t, J = 4.4 Hz), 2.26 (2H, t, J = 6 Hz), 13C-NMR (100, MHz, CDCl3, δ / ppm):
14.2, 24.9, 26.4, 33.0, 34.8, 37.3, 130.9, 134.9.
2-Chloro-1,3,3-trimethylcyclohexene (18)5c: Yield: 40 %; Yellow oil; b.p.
72-75 °C/4mm. Anal. Calcd for C9H15Cl: C, 68.13; H, 9.53 %. Found: C, 68.23;
H, 9.27 %. IR (film, cm-1): 2964, 2933, 2870, 1654, 1458, 1361, 1161, 964.
GC-MS: m/z (relative intensity): 160 (4, M+2), 158 (12, M+), 145 (12), 143 (41),
123 (12), 109 (10), 107 (100, base peak), 91 (41), 81 (25), 79 (34), 77 (28), 53
(23), 41 (51). 1H-NMR (400 MHz, CDCl3, δ / ppm ): 1.06 (6H, s), 1.55 – 1.58
(4H, m), 1.70 (3H, s), 2.03 – 2.04 (2H, m) 13C-NMR (100, MHz, CDCl3, δ / ppm):
18.5, 20.4, 27.8, 32.5, 36.9, 38.8, 128.9, 135.1.
2-Bromo-1,3,3-trimethylcyclopentene (19). New compound. Yield: 64 %;
brown oil; b.p. 69-71 °C/4mm. Anal. Calcd for C8H13Br: C, 50.81; H, 6.93 %.
Found: C, 51.2; H, 7.23 %. IR (film, cm-1): 2956, 2925, 2854, 1656, 1504, 1467,
1441, 1375, 1259, 1080, 1020, 860, 796. GC-MS: m/z (relative intensity): 190
(18, M+2), 188 (18, M+), 175 (83), 173 (86), 94 (100%, base peak), 79 (44), 64
1
(14), 53 (16), 41 (20). H-NMR (400 MHz, CDCl3, δ / ppm): 1.06 (6H, s), 1.70
(3H, s), 1.79 – 1.82 (2H, m), 2.23 – 2.27 (2H, m). 13C-NMR (100, MHz, CDCl3, δ
/ ppm): 16.1, 27.1, 28.2, 34.1, 37.3, 128.3, 139.3.
2-Bromo-1,3,3-trimethylcyclohexene (20). New compound. Yield: 69 %;
brown oil; b. p. 76-78 °C/4mm. Anal. Calcd for C9H15Br: C, 53.22; H, 7.44 %.

SYNTHESIS TRIMETHYLCYCLOALKENES
15
Found: C, 53.42; H, 7.13 %. IR (film, cm-1): 2960, 2927, 2866, 1650, 1456, 1361,
1338, 1280, 1211, 1049, 939, 803, 815, 761. GC-MS: m/z (relative intensity):
204 (26, M+2), 202 (24, M+), 188 (79), 186 (77), 123 (53), 107 (100), 91 (49), 81
1
(42), 67 (21), 52 (25), 41 (44). H-NMR (400 MHz, CDCl3, δ / ppm): 1.05 (6H,
s), 1.53 – 1.58 (4H, m), 1.72 (3H, s), 1.98 – 2.01 (2H, m). 13C-NMR (100, MHz,
CDCl3, δ / ppm): 19.2, 24.4, 29.3, 29.7, 33.8, 39.5, 131.8, 131.9.
2-Iodo-1,3,3-trimethylcyclopentene (21). New compound. Yield: 79 %;
brown oil. b. p. 82-85 °C /4mm. Anal. Calcd for C8H13I: C, 40.70; H, 5.55 %.
Found: C, 40.31; H, 5.71 %. IR (film, cm-1): 2954, 2923, 2866, 1677, 1589, 1446,
1308, 1261, 1018, 802. GC-MS: m/z (relative intensity): 236 (31, M+), 221
(100, base peak), 127(20), 109 (5), 94 (87), 79 (70), 65 (19), 53 (24), 41 (31).
1H-NMR (400 MHz, CDCl3, δ / ppm ): 0.99 (6H, s), 1.75 (3H, s), 1.85 (2H, t, J =
6.96), 2.35 (2H, t, J = 7.44). 13C-NMR (100, MHz, CDCl3, δ / ppm): 19.5, 28.1,
35.6, 36.7, 49.3, 51.8, 109.4, 141.7.
2-Iodo-1,3,3-trimethylcyclohexene (22).6d Yield 82%; brown oil. GC-MS:
m/z (relative intensity): 250 (52, M+), 235 (21), 123(86), 108 (41), 93 (58), 81
1
(100), 67 (28), 53 (26), 41 (56). H-NMR (400 MHz, CDCl3, δ / ppm ): 1.02 (6H,
s), 1.54-1.67 (m, 4H), 1.79 (3H, s), 2.07-2.11 (2H, t, J = 7.76). 13C-NMR (100,
MHz, CDCl3, δ / ppm): 19.4, 31.0, 31.5, 33.7, 37.9, 39.5, 117.3, 137.7.
2-(1′,3′,3′-Trimethylcyclopent-2′-enyl)eth-2-one (23 a).16 Yield 65%; light
Yellow oil; 53-57 °C/1mm. GC-MS: m/z (relative intensity): 152 (27, M+), 109
(100%, base peak), 91 (15), 81(28), 67(82), 55 (17),40 (92).
3-(1′,3′,3′-Trimethylcyclopent-2′-enyl)prop-3-one (23 b). New compound.
Yield: 71 %; light yellow oil; b. p. 64-67 °C/1mm. Anal. Calcd for C11H18O: C,
79.46; H, 10.91%. Found: C, 78.98; H, 10.67 %. IR (film, cm-1): 2881, 2857,
2830, 1718,1450, 1360, 1248, 1017. GC-MS: m/z (relative intensity): 166 (22,
M+), 151 (2), 137 (4), 123 (10), 109 (100%, base peak), 95 (7), 91 (14), 81 (20),
1
67 (59), 57 (43), 55 (19), 40 (73). H-NMR (400 MHz, CDCl3, δ / ppm): 0.96
(3H, t, 3H, J = 3.08 Hz), 0.96 (3H, s), 1.27 (3H, s), 1.26 – 1.38 (2H, m), 1.54 –
1.59 (2H, m), 1.67 (3H, s), 2.09 – 2.13 (2H, m), 2.14 – 2.35 (2H, m). 13C-NMR
(100, MHz, CDCl3, δ / ppm): 15.2, 23.9, 28.8, 31.0, 35.6, 42.2, 46.6, 71.3, 126.5,
137.0, 212.0.
(E)-4-(1′,3′,3′-Trimethylcyclopent-2′-enyl)but-2-en-4-one (23 c). New
compound. Yield: 78 %; light yellow oil; b. p. 69-73 °C/1mm. Anal. Calcd for
C12H18O: C, 80.85; H, 10.18 %. Found: C, 80.36; H, 10.43 %. IR (film, cm-1):
2950, 2890, 1755, 1708, 1635, 1442, 1301, 1075, 950. GC-MS: m/z (relative
intensity): 178 (9, M+), 163 (6), 135 (3), 122 (4), 109 (33), 91 (9), 79 (14), 69
1
(100, base peak), 55 (12), 41 (55). H-NMR (400 MHz, CDCl3, δ / ppm): 1.08
(6H, s), 1.48 (3H, s), 1.75 – 1.85 (5H, m), 1.95 – 2.15 (2H, m), 6.18 – 6.23(1H,
m), 6.84 – 6.93 (1H, m). 13C-NMR (100, MHz, CDCl3, δ / ppm): 15.2, 17.2,
24.2, 31.1, 42.2, 46.9, 126.5, 130.2, 137.2, 138.6, 141.6, 200.2.

16
ACHANNA and SURESH
5-(1′, 3′, 3′-Trimethylcyclopent-2′-enyl)pentan-5-one (23 d).
New
compound. Yield: 83 %; light yellow oil; b. p. 68-72 °C/1mm. Anal. Calcd for
C13H22O: C, 80.35; H, 11.41 %. Found: C, 80.56; H, 11.13 %. IR (film, cm-1):
2880, 2855, 2830, 1720,1450, 1340, 1250, 1020. GC-MS: m/z (relative
intensity): 194 (26, M+), 179 (1), 151 (4), 137 (4), 109 (100%, base peak), 91
1
(10), 85 (74), 67 (52), 57 (70), 41 (43). H-NMR (400 MHz, CDCl3, δ / ppm):
0.93(3H, t, J = 3.08 Hz), 0.99 (3H, s), 1.28(3H, s), 1.29 – 1.36 (4H, m), 1.51 –
1.58 (2H, m), 1.65 (3H, s), 2.07 – 2.11 (2H, m), 2.1 – 2.39 (3H, m). 13C-NMR
(100, MHz, CDCl3, δ / ppm): 12.9, 15.3, 21.4, 24.36, 24.5, 31.0, 42.3, 46.7, 71.3,
126.4, 137.1, 211.5.
6-(1′, 3′, 3′-Trimethylcyclopent-2′-enyl)-hexan-6-one (23 e). New compound.
Yield: 87 %; light yellow oil; b. p 71-74 °C/1mm. Anal. Calcd for C14H24O: C,
80.71; H, 11.61 %. Found: C, 80.34; H, 11.45 %. IR (film, cm-1): 2958, 2931,
1710, 1465, 1335, 12651073. GC-MS: m/z (relative intensity): 208 (24, M+),
193 (2), 165 (2), 137 (4), 109 (100%, base peak), 99 (68), 81 (20), 71 (56) 67
1
(49), 55(19), 43 (73). H-NMR (400 MHz, CDCl3, δ / ppm): 0.87 (3H, m), 0.97
(3H, s), 1.25 (3H, s), 1.28 – 1.35 (6H, m), 1.53 – 1.68 (5H, m), 2.11 – 2.38 (4H,
m). 13C-NMR (100, MHz, CDCl3, δ / ppm): 13.9, 16.3, 22.5, 23.1, 25.0, 29.7,
31.5, 32.1, 43.5, 47.7, 72.3, 127.4, 138.1.
(1,3,3-Trimethylcyclopent-2-enyl)phenylmethanone (23 f). New compound.
Yield: 86 %; yellow oil; b. p. 82-84 °C /1mm. Anal. Calcd for C15H18O: C,
84.07; H, 8.47%. Found: C, 84.74; H, 8.45%. IR (film, cm-1): 2846, 1681, 1600,
1454, 1415, 1323, 1026. GC-MS: m/z (relative intensity): 214 (16, M+), 199
(38), 158 (9), 137 (1), 105 (100%, base peak), 91 (7), 77 (52), 67 (6), 51 (12), 41
(9). 1H-NMR (400 MHz, CDCl3, δ / ppm): 1.22 (6H, s), 1.48 (3H, s), 1.80 (2H,
t, J = 6.8 Hz), 2.41 – 2.48 (2H, m), 7.41 – 7.45 (3H, m), 7.80 – 7.87 (2H, m).
13C-NMR (100, MHz, CDCl3, δ / ppm): 16.0, 26.1, 29.3, 35.7, 39.1, 48.3, 124.4,
127.0, 127.2, 131.1, 138.5, 142.3, 143.5, 197.6.