Preparation and cyclization of some N-(2,2-Dimethylpropargyl) homo- And heteroaromatic amines and the synthesis of some pyrido[2,3-d]pyrimidines

Article abstract of DOI:10.1071/CH04260

The Cu(I) catalyzed cyclization of o-substituted N-(2,2-dimethylpropargyl) anilines yields 8-substituted 2,2-dimethyl-1,2-dihydroquinolines, while m-substituted analogues provide a mixture of 5- and 7-substituted dihydroquinoline systems. This reaction can be extended to 2-amino-N-(2,2- dimethylpropargyl)anthracene, yielding a dihydronaphtho[2,3-f]quinoline product, and to aminoquinoline derivatives, which yield substituted phenanthroline products. Pyridine analogues did not cyclize, apparently because of complexation with the copper reagent. An alternative synthetic approach to these cyclized products, when complexation may be a problem, is illustrated by the following example. 2-Chloro-4-N-(2,2-dimethylpropargyl)pyrimidine was reduced using a Lindlar catalyst to the corresponding alkene which did not undergo an amino-Claisen rearrangement. However, the 5-bromopyrimidine alkene analogue underwent addition with phenylselanyl bromide to give a product that cyclized, using butyllithium, to a pyrido[2,3-d]pyrimidine selenium-containing product from which the selenium moiety could be removed to yield either a dihydro- or a tetrahydro-pyrido[2,3-d]pyrimidine system. A Heck reaction on the 5-bromopyrimidine alkene gave a 5-methylene-6,7-dihydro-5H-pyrrolo[2,3-d] pyrimidine. CSIRO 2005.

Full text of DOI:10.1071/CH04260

Full Paper
CSIRO PUBLISHING
Aust. J. Chem. 2005, 58, 368–374
www.publish.csiro.au/journals/ajc
Preparation and Cyclization of Some N-(2,2-Dimethylpropargyl)
Homo- and Heteroaromatic Amines and the Synthesis
of Some Pyrido[2,3-d]pyrimidines
Michelle A. Holman,A Natalie M. Williamson,A and A. David WardA,B
ADepartment of Chemistry, University of Adelaide, Adelaide SA 5005, Australia.
BCorresponding author. Email: david.ward@adelaide.edu.au
The Cu(i) catalyzed cyclization of o-substituted N-(2,2-dimethylpropargyl)anilines yields 8-substituted 2,2-
dimethyl-1,2-dihydroquinolines, while m-substituted analogues provide a mixture of 5- and 7-substituted dihy-
droquinoline systems. This reaction can be extended to 2-amino-N-(2,2-dimethylpropargyl)anthracene, yielding a
dihydronaphtho[2,3-f ]quinoline product, and to aminoquinoline derivatives, which yield substituted phenanthroline
products. Pyridine analogues did not cyclize, apparently because of complexation with the copper reagent.
An alternative synthetic approach to these cyclized products, when complexation may be a problem, is illustrated
by the following example. 2-Chloro-4-N-(2,2-dimethylpropargyl)pyrimidine was reduced using a Lindlar catalyst to
the corresponding alkene which did not undergo an amino-Claisen rearrangement. However, the 5-bromopyrimidine
alkene analogue underwent addition with phenylselanyl bromide to give a product that cyclized, using butyllithium,
to a pyrido[2,3-d]pyrimidine selenium-containing product from which the selenium moiety could be removed to
yield either a dihydro- or a tetrahydro-pyrido[2,3-d]pyrimidine system. A Heck reaction on the 5-bromopyrimidine
alkene gave a 5-methylene-6,7-dihydro-5H-pyrrolo[2,3-d]pyrimidine.
Manuscript received: 29 October 2004.
Final version: 17 February 2005.
H
Introduction
N
Cl
NH2
CuCl
Cu
ϩ
We have recently described the synthesis (Scheme 1) of
6-substituted 2,2-dimethyl-1,2-dihydroquinolines 1 using a
Cu(i) catalyzed cyclization of 4-substituted N-(2,2-dimethyl-
propargyl)anilines.[1,2] We have shown that these dihydro-
quinolines are useful for the preparation of a range of 3- and
4-substituted and 3,4-disubstituted tetrahydroquinolines.[1]
We have also utilized these reactions as part of an approach
to the synthesis of analogues of virantmycin.[3]
R
R
CuCl
⌬
H
N
R
A wide range of 4-substituted N-(2,2-dimethylpropargyl)-
anilines can be cyclized by this process, with electron-
withdrawing substituents significantly slowing the rate of the
cyclization but otherwise having no effect on the process.[1]
Our studies towards the preparation of virantmycin analogues
showed that while 2,2-dimethylpropargyl chlorides couple
readily to a range of 4-substituted anilines this coupling reac-
tion is sensitive to the size of the substituents at the 2-position,
with 2,2-dibutylpropargyl chlorides not coupling.[2]
In this paper we examine further the scope of the cycliza-
tion of N-(2,2-dimethylpropargyl)anilines by describing our
results on the cyclization of 2- and 3-substituted aniline
derivatives and on the cyclization of similarly substituted het-
erocyclic amine derivatives rather than those from anilines.
The expected products from the cyclization of the substi-
tuted heterocyclic amine derivatives would provide analogues
of virantmycin with extra heteroatoms in the analogue ring
structures.
1
Scheme 1.
Results and Discussion
Synthesis of the N-(2,2-Dimethylpropargyl)
Aromatic Amines
Both o- and m-toluidine and o-anisidine coupled readily with
3-chloro-3-methylbut-1-yne[4] to give the products 2, 3, and
4 respectively (Scheme 2), using the same conditions devel-
oped for the 4-substituted anilines; these results indicate that
the coupling process was not affected by an adjacent ortho
group. m-Phenylenediamine also coupled readily to give 5 as
an unstable oil. Because of the problem of carcinogenicity we
chose not to extend the investigation to aminonaphthalenes,
but we did investigate two anthracene-based compounds.
2-Aminoanthracene coupled readily to give 6. However,
2-aminoanthraquinone did not react with the chloro alkyne,
© CSIRO 2005
10.1071/CH04260
0004-9425/05/050368

N-(2,2-Dimethylpropargyl) Homo- and Heteroaromatic Amines and Pyrido[2,3-d]pyrimidines
369
Me
OMe
Me
H
N
H
N
H
N
H
N
H
N
H
N
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
2
3
4
5
6
Scheme 2.
Me
H
N
Me
Me
Me
OMe
H
N
H
N
Me
Me
H
N
Me
Me
Me
Me
Me
Me
NH
Me
7
8
9
10
11
Scheme 3.
H
N
H
N
Me
Me
Me
Me
MeO
N
N
N
Me
NH
12
13
14
Me
Me
Scheme 4.
Me
Me
Me
Me
MeO
H
N
H
N
Me
Me
Me
Me
NH
HN
N
Me
NH
Me Me
N
N
N
N
15
16
17
18
19
Scheme 5.
even after an extended reaction period. Presumably this lack
of reactivity is a consequence of the deactivating influence
of one of the carbonyl groups on the amine.
amines could be complicated, in some cases, by the pos-
sibility of coordination to the copper used in the coupling
step. This was indeed the case with 2- and 4-aminopyridine,
and in both cases a dark precipitate was obtained from the
reaction mixture; some starting material was also recovered.
Workup of the precipitate obtained from the reaction using
4-aminopyridine and EDTA (ethylenediaminetetraacetic
acid) returned 4-aminopyridine only. Surprisingly, it has been
claimed that 4-aminopyridine underwent the coupling reac-
tion, although no details of the product were provided.[5]
Because of suggestions[6,7] that the actual reagent in these
coupling reactions was a 1-chloroallene, formed by rear-
rangement of the carbocation from the propargyl chloride,
the reaction of 2-aminopyridine with 1-bromo-3-methylbuta-
1,2-diene was investigated as an alternative approach, both
in the absence and presence of copper(i). In each case both
starting materials were recovered after workup, with no sign
of a coupled product.
Cyclization of the N-(2,2-Dimethylpropargyl)
Aromatic Amines
Both of the ortho-substituted anilines 2 and 4 cyclized using
our standard conditions to give the corresponding dihydro-
quinolines 7 and 9 respectively (Scheme 3), in moderate
yields. As expected, the meta-substituted aniline derivative
3 cyclized in the two possible ways to give a 1 : 1 mixture of
8 and 10. The m-phenylenediamine derivative 5 gave only an
intractable product with no signals attributable to the double-
bond hydrogens of a dihydroquinoline system in the 1H NMR
spectrum of the total product.The 2-aminoanthracene deriva-
tive 6 cyclized readily to give only the naphthoquinoline 11
in moderate yield. The formation of only one of the two pos-
sible cyclization products is presumably a consequence of
bond fixation in the anthracene system. Other examples of
cyclization preference for this reason are described below.
Three aminoquinolines were coupled with 3-chloro-3-
methylbut-1-yne utilizing the same conditions used for the
aromatic amines described above to give the corresponding
N-substituted quinolines 12, 13, and 14 (Scheme 4). The
poor yield obtained in the case of 14 may be due, in part,
to complexation of the starting material and/or the product
with copper.
Preparation and Cyclization of N-(2,2-Dimethylpropargyl)
Heterocyclic Aromatic Amines
It was expected that the preparation of the N-(2,2-
dimethylpropargyl) derivatives of heterocyclic aromatic

370
M. A. Holman, N. M. Williamson and A. D. Ward
H
N
Synthesis of the Pyrido[2,3-d]pyrimidines 29–31
N
CuCl
Our experience with the 2-aminopyridine system suggested
that it would be difficult to cyclize a pyrimidine propar-
gylamine by using copper catalysis, and so we approached
the synthesis of the desired cyclized product in a differ-
ent way. The pyrimidine derivative 22 was easier to prepare
by a nucleophilic attack on 2,4-dichloropyrimidine, rather
than by the general method used for the aniline systems.[2]
Accordingly the propargylamine 23 was prepared and treated
with 2,4-dichloropyrimidine to give 22 as the major prod-
uct in a mixture that contained two regioisomers (ratio 9 : 1;
Scheme 7).
⌬/toluene
20
21
Scheme 6.
The N-substituted aminoquinolines 12, 13, and 14
cyclized, using the standard conditions, to give moderate
yields of a single phenanthroline product, 15, 17, and 19
(Scheme 5) respectively in each case. That the cyclization of
1
12 yielded 15, rather than 16, was shown by the H NMR
The major isomer was purified by chromatography and
its structure shown to be 22 by an X-ray crystal struc-
ture determination.[8] The protecting trimethylsilyl group
was removed with tetrabutylammonium fluoride and the
alkyne product 24 was reduced by catalytic hydrogenation
with a Lindlar catalyst to give the alkene 25 which failed
to undergo an amino-Claisen rearrangement using condi-
tions successfully employed for related aniline systems.[2]
Consequently, the sequence was repeated with 5-bromo-2,4-
dichloropyrimidine (Scheme 8) to yield the alkene 27. In
this case the precaution of protecting the alkyne functionality
as its trimethylsilyl derivative was found to be unnecessary.
A Heck reaction on 27 gave only the 1,5-exo cyclization prod-
uct 28 as indicated by a 13C DEPT NMR spectrum which
showed that the two alkene carbons at δ 137.6 and 115.4
were quarternary and secondary respectively. The alkene 27
reacted readily with phenylselanyl bromide to give an unsta-
ble addition product, which was cyclized, in situ, by the
addition of butyllithium to yield the bicyclic selenide 29.
The size of the newly created ring, and hence the mode of
addition of the phenylselanyl bromide, was confirmed by a
reductive removal of the phenylselanyl group to give a prod-
spectrum of the product which showed a singlet at δ 8.32
attributable to the hydrogen at position 2 which is deshielded
by the adjacent aromatic ring nitrogen (the corresponding
signal in 12 is at δ 8.48). Structure 16 would not be expected
to have a signal in this region. The signals for the double-
bond hydrogens of 15 are at δ 5.74 and 6.94. The former is
a doublet of doublets due to coupling (10 Hz) to the adjacent
alkene hydrogen as well as a W-coupling (2.2 Hz) to the NH.
The starting material 7 has a signal at 7.63 (J 2.9 Hz), due
to the hydrogen at position 4; a signal of this type is absent
from the spectrum of the product 15.
Cyclization of 13 also formed only one product, the
phenanthroline 17, whose structure was confirmed by its 1H
NMR spectrum, which showed two doublets in the aromatic
region(δ6.93and7.65, eachwithacouplingconstantof9 Hz)
due to the hydrogens (H5 and H6) of the benzenoid portion
of the structure. In addition, the three signals for the hydro-
gens of the heterocyclic aromatic ring (H9, H10, and H11)
appeared at δ 8.58 (J 4.2 Hz), 7.25 (J 4.2, 8.5 Hz), and 8.15
(J 8.5 Hz) respectively.The two alkene hydrogens appeared as
a doublet at δ 6.87 (J 9.9 Hz) and a doublet of doublets at 5.35
(J 2.0, 9.9 Hz) for H1 and H2 respectively.The small coupling
observed for H1 is presumably caused by a W-coupling to the
NH. The alternative product, 18, would be expected to show
two singlets for H5 and H10. The formation of only one of
two possible products in the cyclizations of 12 and 13 can be
attributed to bond fixation.
1
uct 30 whose H NMR spectrum showed the presence of
two adjacent methylene groups. The phenylselanyl group in
29 could be oxidatively removed, in poor yield, with either
sodium periodate or hydrogen peroxide to give the desired
dihydropyrido[2,3-d]pyrimidine 31.
Cyclization of 14 gave only one product 19 as expected,
which showed signals at δ 5.48 (J 2.2, 9.8 Hz) and 6.73
(J 9.8 Hz) for the alkene hydrogens, H8 and H9 respectively.
Again, the small coupling observed for H9 is probably due to
a W coupling with the adjacent NH. The low yield obtained
for this reaction may also be, in part, caused by complexation
of the starting material and/or the product with copper.
A propargylaniline 20, unsubstituted at position 2 of
the propargyl chain, was prepared using the standard
procedure.[2] The cyclization procedure for this material,
which yielded 6-methylquinoline 21 (Scheme 6) had to be
modified since it was found that as soon as any quinoline
was produced it formed a complex with the copper present,
thus removing copper from the catalytic cycle. The cycliza-
tion was carried out with one equivalent of cuprous chloride.
The workup procedure for the reaction was also modified as
the resulting copper–quinoline complex needed to be broken
up using EDTA.
Conclusions
The cyclization of p-substituted N-(2,2-dimethylpropargyl)
anilines to yield substituted 2,2-dimethyl-1,2-dihydroquino-
lines can be extended to o- and m-substituted analogues,
although in the latter case two regioisomers are produced.The
reaction can also be used with a 2-aminoanthracene analogue,
to yield 3,3-dimethyl-3,4-dihydronaphtho[2,3-f]quinoline.
However, 2-aminoanthraquinone did not form the precursor
necessary for the cyclization process.
While N-(2,2-dimethylpropargyl)quinolines can be read-
ily prepared and cyclized to substituted phenanthrolines,
pyridine systems do not form the propargyl derivative neces-
sary for the cyclization, apparently because complexation of
the amine with the copper(i) reagent prevents the coupling
process.
In the case of an aminopyrimidine system, which
presumably would be likely to suffer from the same

N-(2,2-Dimethylpropargyl) Homo- and Heteroaromatic Amines and Pyrido[2,3-d]pyrimidines
371
Me Me
H
N
H
N
H
N
H2N
SiMe3
Me
Me
Me
Me
Cl
N
Cl
Cl
N
Cl
N
Me
Me
Cl
N
Bu4NF
H2
23
N
N
N
N
Lindlar
NEt3/DMF
22
24
25
SiMe3
Scheme 7.
H
H
N
Me Me
H
N
Me
Me
Me
Me
Cl
N
Cl
Cl
N
N
Cl
N
Cl
N
Me
Me
H2N
Heck
H2
N
N
Lindlar
N
N
NEt3/DMF
Br
Br
Br
26
27
28
PhSeBr
H
N
H
H
Me
Me
Me
Me
N
N
Cl
N
Cl
N
Cl
N
NaIO4
BuLi
0ºC
Me
Me
N
N
N
SePh
SePh
Br
31
29
Br
(i) BuLi
(ii)H2O
H
N
Me
Me
Cl
N
N
30
Scheme 8.
complexation observed with aminopyridines, the cyclization
product was prepared by a different approach. The
N-(2,2-dimethylpropargyl) derivative of 4-amino-5-bromo-
2-chloropyrimidine was reduced to an alkene which under-
went an addition reaction with phenylselanyl bromide to give
an adduct which was cyclized, using butyllithium, and the
selenium moiety removed, using an oxidative elimination
process, to provide a substituted pyrido[2,3-d]pyrimidine in
poor yield.A Heck reaction onthealkenegaveasubstituted5-
methylene-6,7-dihydro-5H-pyrrolo[2,3-d]pyrimidine. These
last two reactions further illustrate the synthetic utility of
N-(2,2-dimethylpropargyl)derivativesofheterocyclicamines.
General Procedure for the Coupling of 3-Chloro-3-methylbut-1-yne
with Aromatic Amines
A solution of 3-chloro-3-methylbut-1-yne[4] (approx. 7 mmol) in
tetrahydrofuran (1 mL) was added slowly to a stirred mixture of the cor-
responding aromatic amine (approx. 5 mmol), cuprous chloride (50 mg),
copper bronze powder (50 mg), and triethylamine (approx. 7 mmol)
in tetrahydrofuran (5 mL) and water (0.5 mL), and the resulting mix-
ture stirred at room temperature under an atmosphere of nitrogen for
30–120 min. Water (10 mL) was added and the organic phase separated
and combined with the dichloromethane extracts of the aqueous phase.
The combined organic extracts were dried and the solvent was removed.
The residue was purified by flash chromatography. By this means the
following compounds were prepared.
2-Methyl-N-(2-methylbut-3-yn-2-yl)aniline 2 was obtained from
o-toluidine as an orange oil (28%) after elution with light
petroleum/ethyl acetate (85 : 15) (Found: 173.1197. C12H15N requires
173.1204). νmax (CDCl3)/cm−1 3415, 3300, 1600, 1505. δH 7.29 (1H,
dd, J 0.9, 8.2, ArH), 7.10 (2H, m, ArH), 6.71 (1H, dt, J 0.9, 7.3, ArH),
3.53 [1H, br s (exchanges with D2O), NH], 2.37 (1H, s, alkyne H), 2.13
(3H, s,ArMe), 1.65 (6H, s, Me). m/z 173 (41%, M), 158 (100), 143 (25),
107 (85), 106 (77).
3-Methyl-N-(2-methylbut-3-yn-2-yl)aniline 3 was obtained from
m-toluidine as a red oil (83%) after elution with light petroleum/ethyl
acetate (85 : 15) (Found: 173.1203. C12H15N requires 173.1204). νmax
(CDCl3)/cm−1 3400, 3300, 1605, 1510. δH 7.09 (1H, t, J 7.7, ArH),
6.78 (1H, dd, J 2.3, 8.3, ArH), 6.73 (1H, br s, ArH), 6.62 (1H, d, J 7.7,
ArH), 3.61 [1H, br s (exchanges with D2O), NH], 2.36 (1H, s, alkyne
H), 2.29 (3H, s, ArMe), 1.60 (6H, s, Me). m/z 173 (65%, M), 158 (100),
143 (10), 107 (44).
2-Methoxy-N-(2-methylbut-3-yn-2-yl)aniline 4 was obtained from
o-anisidine as a pale orange oil (46%) after elution with light
petroleum/ethyl acetate (85 : 15) (Found: 189.1158. C12H15NO requires
189.1154). νmax (CDCl3)/cm−1 3420, 3300, 1600, 1505 1225. δH 7.27
Experimental
General Experimental Conditions
Melting points were determined on a Kofler hot stage apparatus
equippedwithaReichertmicroscopeandareuncorrected. Infraredspec-
tra were recorded on a Jasco A102 grating spectrometer. Proton NMR
spectra (δH) were recorded on a Bruker ACP300 spectrometer operat-
ing at 300 MHz in (D)chloroform solution (unless otherwise stated)
using tetramethylsilane as an internal standard. Chemical shifts are
quoted as δ in parts per million and coupling constants (J) are given
in Hertz. Electron-impact mass spectra (m/z) were recorded at 70 eV
on a VG ZAB 2HF spectrometer. Microanalyses were performed by the
Canadian Microanalytical Service Ltd or by the Chemical and Micro-
analytical Service Pty Ltd, Melbourne. Accurate mass measurements
(HRMS) were made using electron impact on either an AEI MS3074
spectrometer or by the University of Melbourne on a JEOL AX505H
spectrometer. Flash chromatography refers to nitrogen pressure driven
rapid chromatography[9] using Merck silica gel, pore diameter 60 Å.

372
M. A. Holman, N. M. Williamson and A. D. Ward
(1H, dd, J 1.5, 7.9, ArH), 6.88 (1H, dt, J 1.5, 7.9, ArH), 6.74 (2H, m,
ArH), 4.35 [1H, br s (exchanges with D2O), NH], 3.83 (3H, s, OMe),
2.36 (1H, s, alkyne H), 1.64 (6H, s, Me). m/z 189 (43%, M), 174 (100),
159 (12), 144 (23), 123 (54).
3400, 1630, 1600, 1500. δH 6.58 (3H, m, ArH), 6.26 (1H, d, J 9.7,
C=CH), 5.45 (1H, d, J 9.7, C=CH), 4.17 [1H, br s (exchanges with
D2O), NH], 3.81 (3H, s, OMe), 1.31 (6H, s, Me). m/z 189 (9%, M), 174
(100), 159 (46), 131 (14).
N,Nꢀ-Bis-(2-methylbut-3-yn-2-yl)-m-phenylenediamine 5wasobtai-
ned from m-phenylenediamine as an unstable orange oil (31%) after
elution with light petroleum/ethyl acetate (60 : 40) (Found: 240.1615.
C16H20N2 requires 240.1626.) δH 6.98 (1H, t, J 8.1, ArH), 6.72 (1H, t,
J 2.3, ArH), 6.32 (2H, dd, J 2.3, 8.1, ArH), 3.61 [2H, br s (exchanges
with D2O), NH], 2.36 (2H, s, alkyne H), 1.61 (12H, s, Me). m/z 240
(95%, M), 225 (100), 210 (25), 209 (30), 173 (90), 159 (75).
2-Amino-N-(2-methylbut-3-yn-2-yl)anthracene 6 was obtained from
2-aminoanthracene (obtained by reduction of 2-aminoanthraquinone
with Zn/NaOH[10]) as orange needles (22%), mp 85–87◦C, after elu-
tion with light petroleum/ethyl acetate (80 : 20) and crystallization from
dichloromethane/light petroleum (Found: 259.1353. C19H17N requires
259.1361). νmax (CDCl3)/cm−1 3415, 3300, 1625, 1510. δH 8.23 (1H,
s, ArH), 8.19 (1H, s, ArH), 7.88 (2H, m, ArH), 7.79 (1H, d, J 9.0,
ArH), 7.35 (3H, m, ArH), 6.95 (1H, dd, J 2.3, 9.0, ArH), 3.91 [1H, br s
(exchanges with D2O), NH], 2.45 (1H, s, alkyne H), 1.70 (6H, s, Me).
m/z 259 (50%, M), 244 (72), 193 (69), 165 (100), 84 (29).
3-Amino-N-(2-methylbut-3-yn-2-yl)quinoline 12 was obtained from
3-aminoquinoline as orange prisms (63%), mp 102–104◦C, after elu-
tion with light petroleum/ethyl acetate (35 : 65) and crystallization from
dichloromethane/light petroleum. νmax (CH2Cl2)/cm−1 3650, 3300,
1600, 1505, 1550. δH 8.48 (1H, d, J 2.9, ArH), 7.95 (1H, m, ArH), 7.68
(1H, m, ArH), 7.63 (1H, d, J 2.9, ArH), 7.45 (2H, m, ArH), 4.08 [1H, br
s (exchanges with D2O), NH], 2.44 (1H, s, alkyne H), 1.69 (6H, s, Me).
m/z 210 (55%, M), 195 (80), 168 (20), 144 (90), 176 (30), 69 (100).
6-Amino-N-(2-methylbut-3-yn-2-yl)quinoline 13 was obtained from
6-aminoquinoline (obtained from 6-nitroquinoline by reduction
with H2/Pd–C) as an orange oil (28%) after elution with
dichloromethane/methanol (95 : 5) (Found: 210.1152. C14H14N2
requires 210.1157). νmax (CDCl3)/cm−1 3390, 3300, 1610, 1505, 1540.
δH 8.60 (1H, d, J 3.0, ArH), 7.96 (1H, dd, J 1.1, 8.3, ArH), 7.89 (1H, d,
J 9.1, ArH), 7.22 (3H, m, ArH), 4.29 [1H, br s (exchanges with D2O),
NH], 2.44 (1H, s, alkyne H), 1.67 (6H, s, Me). m/z 211 (40%, M + H),
196 (100), 144 (55), 116 (15).
2,2,5- and 2,2,7-Trimethyl-1,2-dihydroquinoline 10 and 8, respec-
tively, were obtained as a yellow oil (70%) after elution with light
petroleum/ethyl acetate (85 : 15) which was an inseparable 1 : 1 mixture
of the 2,2,5- and 2,2,7-trimethyl isomers (Found: 173.1196. C12H15
N
requires 173.1204). νmax (CDCl3)/cm−1 3400, 1640 1620, 1600, 1500.
δH 6.85 (1H, t, J 7.7, ArH), 6.77 (1H, d, J 7.5, ArH), 6.43 (3H, m, ArH
and C=CH), 6.25 (1H, m, ArH), 6.23 (1H, br s, ArH), 5.50 (1H, d,
J 9.9, C=CH), 5.40 (1H, d, J 9.7, C=CH), 3.60 [2H, br s (exchanges
with D2O), NH], 2.24 (3H, s, ArMe), 2.20 (3H, s, ArMe), 1.29 [12H, s,
ArMe (2 Me for each isomer)]. m/z 173 (12%, M), 158 (100).
3,3-Dimethyl-3,4-dihydronaphtho[2,3-f]quinoline 11 was obtained
as a viscous orange oil (55%) after elution with light petroleum/ethyl
acetate (85 : 15) (Found: 259.1360. C19H17N requires 259.1361). νmax
(CDCl3)/cm−1 3435, 1630, 1555, 1540. δH 8.31 (1H, s, ArH), 8.18 (1H,
s, ArH), 7.87 (2H, t, J 8.1, ArH), 7.68 (1H, d, J 9.0, ArH), 7.34 (2H, m,
ArH), 7.13 (1H, d, J 9.8 Hz, C=CH), 6.74 (1H, d, J 9.0, ArH), 5.54 (1H,
dd, J 1.1, 9.8, C=CH), 3.92 [1H, br s (exchanges with D2O), NH], 1.36
(6H, s, Me). m/z 259 (11%, M), 244 (88), 122 (16), 86 (64), 84 (100).
3,3-Dimethyl-3,4-dihydro-4,6-phenanthroline 15 was obtained as an
unstableorangeoil(33%)afterelutionwithlightpetroleum/ethylacetate
(25 : 75). δH 8.32 (1H, br s, ArH), 7.92 (1H, d, J 8.7 Hz, ArH), 7.83 (1H,
d, J 9.3, ArH), 7.42 (2H, m, ArH), 6.94 (1H, d, J 10.0, C=CH), 5.74
(1H, dd, J 2.2, 10.0, C=CH), 4.16 [1H, br s (exchanges with D2O), NH],
1.37 (6H, s, Me).
3,3-Dimethyl-3,4-dihydro-4,7-phenanthroline 17 was obtained as a
yellow oil (42%) after elution with dichloromethane/methanol (95 : 5)
(Found: 210.1146. C14H14N2 requires 210.1157). νmax (CH2Cl2)/cm−1
3370, 1620, 1590, 1540, 1500. δH 8.58 (1H, d, J 4.2, ArH), 8.15 (1H,
d, J 8.5, ArH), 7.65 (1H, d, J 9.0, ArH), 7.25 (1H, dd, J 4.2, 8.5, ArH),
6.93 (1H, d, J 9.0, ArH), 6.87 (1H, d, J 9.9, C=CH), 5.35 (1H, dd,
J 2.0, 9.9, C=CH), 4.23 [1H, br s (exchanges with D2O), NH], 1.34
(6H, s, Me). m/z 211 (15%, M + H), 196 (100), 195 (20), 86 (35),
84 (60).
6-Methoxy-2,9,9-trimethyl-9,10-dihydro-1,10-phenanthroline 19
was obtained as a glassy, red-brown solid, (30%), mp 78–79◦C (dec.),
after elution with dichloromethane (Found: 254.1425. C16H18N2O
requires 254.1425). νmax (CDCl3)/cm−1 3300, 1620, 1595, 1500, 1550.
δH 7.74 (1H, d, J 8.3, ArH), 7.10 (1H, d, J 8.3, ArH), 6.73 (1H, d, J 9.8,
C=CH), 6.25 (1H, s, ArH), 5.94 [1H, br s (exchanges with D2O), NH],
5.48 (1H, dd, J 2.2, 9.8, C=CH), 2.64 (3H, s, ArMe), 1.41 (6H, s, Me).
m/z 254 (11%, M), 239 (100), 224 (36), 213 (48), 196 (23), 170 (32).
N-Propargyl-4-methylaniline 20 was obtained in the following
way. Propargyl bromide (0.37 mL, 4.2 mmol) was added dropwise
under an atmosphere of nitrogen to a stirred mixture of p-toluidine
(0.45 g, 4.2 mmol) and potassium carbonate (0.87 g, 6.3 mmol) in
dichloromethane (10 mL) and the resulting mixture stirred at room
temperature under an atmosphere of nitrogen for 24 h. Water (10 mL)
was added and the organic phase separated and combined with the
dichloromethane extracts of the aqueous phase. The combined organic
extracts were dried and the solvent was removed. The residue was
purified by flash chromatography; elution with light petroleum/ethyl
acetate (70 : 30) provided a yellow solid which was recrystallized from
dichloromethane/light petroleum to give the aniline (0.15 g, 25%) as
colourless needles, mp 46–47◦C (Found: 145.0886. C10H11N requires
145.0891). νmax (CH2Cl2)/cm−1 3405, 3300, 1605, 1500. δH 7.03 (2H,
d, J 8.5, ArH), 6.62 (2H, d, J 8.5, ArH), 3.91 (2H, d, J 2.4 Hz, CH2),
3.74 [1H, br s (exchanges with D2O) NH], 2.25 (3H, s, Me), 2.20 (1H,
t, J 2.4 Hz, alkyne H). m/z 145 (100%, M), 144 (55), 130 (52), 106 (50),
91 (24).
8-Amino-6-methoxy-2-methyl-N-(2-methylbut-3-yn-2-yl)quinoline
14 was obtained from 8-amino-6-methoxy-2-methylquinoline[11] as off-
white prisms (12%), mp 110–111◦C, after elution with dichloromethane
and crystallization from dichloromethane/light petroleum (Found:
254.1406. C16H18N2O requires 254.1419). δH 7.82 (1H, d, J 8.3, ArH),
7.18 (1H, d, J 8.3, ArH), 6.95 (1H, d, J 2.5, ArH), 6.43 [1H, br s
(exchanges with D2O), NH], 6.38 (1H, d, J 2.5, ArH), 3.89 (3H, s,
OMe), 2.64 (3H, s, ArMe), 2.41 (1H, s, alkyne H), 1.77 (6H, s, Me). m/z
254 (40%, M), 239 (100), 213 (10), 196 (10), 188 (20).
General Procedure for the Cyclization of
N-(2,2-Dimethylpropargyl)anilines
A mixture of the N-propargylaniline (approx. 2 mmol) and cuprous
chloride (50 mg) in toluene (5 mL) was refluxed under an atmosphere
of nitrogen for 30–90 min. The reaction mixture was cooled, water
(5 mL) added, and the organic phase separated and combined with the
dichloromethane extracts of the aqueous phase. The combined organic
extracts were dried and the solvent was removed. The residue was puri-
fied by flash chromatography. By this means the following compounds
were prepared.
2,2,8-Trimethyl-1,2-dihydroquinoline 7 was obtained as a yellow oil
(52%) after elution with light petroleum/ethyl acetate (85 : 15) (Found:
173.1191. C12H15N requires 173.1204). νmax (CDCl3)/cm−1 3415,
1630, 1600, 1505. δH 6.86 (1H, d, J 7.5, ArH), 6.78 (1H, d, J 7.5, ArH),
6.51 (1H, t, J 7.5, ArH), 6.26 (1H, d, J 9.7, C=CH), 5.45 (1H, d, J 9.7,
C=CH), 3.50 [1H, br s (exchanges with D2O), NH], 2.07 (3H, s,ArMe),
1.32 (6H, s, Me). m/z 173 (2%, M), 158 (100), 157 (24).
Also obtained from this reaction was the dialkyne N,N-dipropargyl-
4-methylaniline (20 mg, 3%) as an orange oil (Found: 183.1042.
C13H13N requires 183.1048). νmax (CDCl3)/cm−1 3300, 1610, 1505.
δH 7.10 (2H, d, J 8.7, ArH), 6.89 (2H, d, J 8.7, ArH), 4.08 (4H, d, J 2.4,
CH2), 2.28 (3H, s, Me), 2.24 (2H, t, J 2.4, alkyne H). m/z 183 (100%,
M), 168 (24), 167 (30), 144 (33), 143 (29), 142 (28).
2,2-Dimethyl-8-methoxy-1,2-dihydroquinoline 8 was obtained as a
yellow oil (63%) after elution with light petroleum/ethyl acetate (85 : 15)
(Found: 189.1150. C12H15NO requires 189.1154). νmax (CDCl3)/cm−1

N-(2,2-Dimethylpropargyl) Homo- and Heteroaromatic Amines and Pyrido[2,3-d]pyrimidines
373
6-Methylquinoline 21 was obtained in the following way. A mix-
ture of 4-methyl-N-propargylaniline (0.10 g, 0.69 mmol) and cuprous
chloride (70 mg, 0.69 mmol) in toluene (5 mL) was refluxed under an
atmosphere of nitrogen for 30 min. The reaction mixture was cooled,
diluted with dichloromethane (5 mL), and extracted with hydrochlo-
ric acid (10%, 3 × 10 mL). The aqueous extracts were combined and
EDTA (0.25 g, 0.7 mmol) was added with stirring. The resulting mix-
ture was basified to pH 12 with solid sodium hydroxide and extracted
with dichloromethane (3 × 15 mL).The combined organic extracts were
dried and the solvent was removed. The residue was purified by flash
chromatography; elution with light petroleum/ethyl acetate (70 : 30)
gavethequinoline (38 mg, 38%)asalight-sensitiveorangeoil, whose1H
NMR spectrum was identical to that published.[12] νmax (CH2Cl2)/cm−1
1630, 1600, 1575, 1500. δH 8.89 (1H, m, ArH), 8.03 (2H, m, ArH), 7.53
(2H, m, ArH), 7.34 (1H, br s, ArH), 2.52 (3H, s, Me). m/z 143 (100%,
M), 142 (46), 120 (7), 115 (16).
1,1-Dimethyl-3-trimethylsilyl-2-propynylamine 23 was obtained in
the following way. 1,1-Dimethylpropargylamine (1.0 g, 12.05 mmol) in
tetrahydrofuran (15 mL) was cooled to −78◦C, and butyllithium (2.0 M,
6.62 mL, 13.25 mmol) was added slowly. After 30 min chlorotrimethyl-
silane (1.44 g, 13.25 mmol) was added and the mixture was allowed to
warm to room temperature and then stirred overnight. Water (5 mL) was
added and the mixture was extracted with dichloromethane (3 × 15 mL).
The combined organic extracts were washed with saturated sodium
bicarbonate solution (15 mL), dried, the solvent was removed under
reduced pressure, and the residue was distilled to give the amine as
a colourless liquid (1.56 g, 84%), bp 67–69◦/24 mm (Found: 155.1147.
C8H17NSi requires 155.1130). νmax (film)/cm−1 3370, 3300, 2160. δH
1.95 (2H, br s, NH2), 1.42 (6H, s, CMe), 0.18 (9H, s, SiMe). m/z 155
(5%, M), 140 (100).
2-Chloro-4-(1,1-dimethyl-3-trimethylsilyl-2-propyn-1-ylamino)-
pyrimidine 22 and 4-chloro-2-(1,1-dimethyl-3-trimethylsilyl-2-propyn-
1-ylamino)pyrimidine were obtained in the following way. 2,4-
Dichloropyrimidine (0.123 g, 0.823 mmol), the amine 23, and tri-
ethylamine (0.10 g, 0.99 mmol) were heated in dimethylformamide
(5 mL) at 90◦C for 5 h. Solvent was removed from the cooled solution
under reduced pressure. The residue was dissolved in dichloromethane
(10 mL), washed with sodium hydroxide solution (1 M, 2 × 10 mL),
dried, and the solvent removed. The residue was chromatographed
(dichloromethane/methanol, 98 : 2) to afford a yellow solid that con-
tained both regioisomers in a ratio of 9 : 1. Fractional crystallization
(ethanol/water) gave the major isomer 22 as colourless prisms (0.174 g,
79%), mp 89–90◦C (Found: C 54.3, H 6.6, N 15.7; M 267.0966.
C12H18ClN3Si requires C 53.8, H 6.7, N 15.7%; M 267.0959). νmax
(Nujol)/cm−1 3272, 2164, 1674, 1600. δH 8.13 (1H, d, J 6.0, ArH), 6.82
(1H, d, J 6.0, ArH), 5.42 (1H, br s, NH), 1.62 (6H, s, CMe), 0.15 (9H, s,
SiMe). m/z 267/269 (70%, M), 252/254 (100), 232 (40). The 1H NMR
spectrum of the minor product was obtained from the spectrum of the
mother liquor material, by subtraction. δH 7.99 (1H, d, J 6.0, ArH), 6.29
(1H, d, J 6.0, ArH), 5.40 (1H, br s, NH), 1.46 (6H, s, CMe), 0.12 (9H,
br s, SiMe).
the solvent evaporated to yield a yellow solid which was recrystallized
from ethanol/water to yield the alkene as colourless needles (178 mg,
90%), mp 84.5–85.5◦C (Found: C 54.8, H 6.1, N 21.6; M 197.0735.
C9H12ClN3 requires C 54.7, H 6.1, N 21.2%; M 197.0720). νmax
(CH2Cl2)/cm−1 3298, 1620. δH 8.00 (1H, d, J 6.0, ArH), 6.39 (1H,
d, J 6.0, ArH), 5.95 (1H, dd, Jcis 10, Jtrans 17, CH=CH2), 5.51 (1H, br s,
NH), 5.21 (1H, d, Jcis 10, CH=CH2), 5.20 (1H, d, Jtrans 17, CH=CH2),
1.46 (6H, s, CMe). m/z 197/199 (23%, M), 182/184 (100), 162 (14).
5-Bromo-2-chloro-4-(1,1-dimethyl-2-propyn-1-ylamino)pyrimidine
26 and 5-bromo-4-chloro-2-(1,1-dimethyl-2-propyn-1-ylamino)pyrimi-
dine were obtained in the following way. 5-Bromo-2,4-dichloropyrimi-
dine[13] (0.572 g, 2.5 mmol), 1,1-dimethylpropargylamine (0.32 g,
3.8 mmol), and triethylamine (0.38 g, 3.8 mmol) were heated in
dimethylformamide (10 mL) at 90◦C for 5 h. The solvent was evap-
orated from the cooled solution and the residue was dissolved
in dichloromethane, washed with sodium hydroxide solution (1 M,
2 × 15 mL), dried, and the solvent evaporated. The yellow oil thus
obtained was chromatographed (dichloromethane) to give a solid which
was recrystallized from ethanol/water to give the major isomer 26 as
colourless needles (0.523 g, 76%), mp 81–81.5◦C (Found: C 39.5, H 3.4,
N 15.4; M 272.9679. C9H9BrClN3 requires C 39.4, H 3.3, N 15.3%; M
272.9670). νmax (Nujol)/cm−1 3420, 3216. 2158, 1640, 1600. δH 8.17
(1H, s, ArH), 5.61 (1H, br s, NH), 2.39 (1H, s, alkyne H), 1.80 (6H, s,
Me). m/z 273/275/277 (100%, M), 258/260/262 (92).
The 1H NMR spectrum of the minor isomer also present was deter-
mined from a spectrum of the mother liquor material, by subtraction.
δH 8.38 (1H, s, ArH), 5.48 (1H, br s, NH), 2.31 (1H, s, alkyne H), 1.72
(6H, s, Me).
5-Bromo-2-chloro-4-(1,1-dimethyl-2-propen-1-ylamino)pyrimidine
27 was obtained in the following way. The alkyne 26 was reduced as
described for the alkyne 24 to give the alkene as colourless needles
(91%) after recrystallization from ethanol/water, mp 57–58◦C (Found:
C 39.0, H 4.0, N 15.2. C9H11BrClN3 requires C 39.1, H 4.0, N 15.2%).
νmax (Nujol)/cm−1 3316, 1582. δH 8.11 (1H, s, ArH), 6.12 (1H, d,
Jcis 10, Jtrans 17, CH=CH2), 5.56 (1H, br s, NH), 5.18 (1H, d, Jtrans
17, CH=CH2), 5.12 (1H, d, Jcis 10, CH=CH2), 1.60 (6H, s, Me). m/z
275/277/279 (38%, M), 260/262/264 (100).
2-Chloro-6,6-dimethyl-5-methylene-6,7-dihydro-5H-pyrrolo[2,3-
d]pyrimidine 28 was obtained in the following way. The alkene
27 (20 mg, 0.075 mmol), triethylamine (0.22 g, 2.2 mmol), palla-
dium acetate (2 mg, 0.0075 mmol), and tri-o-tolylphosphine (5 mg,
0.015 mmol) were heated and stirred at 100◦C for 16 h in a sealed
tube. The mixture was diluted with water and extracted with ether
(3 × 15 mL); the organic extracts were dried and evaporated.The residue
was chromatographed, using hexane/dichloromethane, to afford the
title compound as a colourless oil (10 mg, 70%) (Found: C 55.4,
H 5.1, N 21.2. C9H10Cl3 requires C 55.3, H 5.2, N 21.5%). νmax
(CH2Cl2)/cm−1 3270, 1622. δH 8.09 (1H, s, ArH), 6.65 (1H, br s, NH),
5.54 (1H, s, C=CH2), 5.13 (1H, s, C=CH2), 1.44 (6H, s, Me). m/z
195/197 (24%, M), 180/182 (100).
2-Chloro-7,7-dimethyl-6-phenylselanyl-5,6,7,8-tetrahydropyrido[2,
3-d]pyrimidine 29 was obtained in the following way. Phenylselanylbro-
mide (0.373 g, 1.58 mmol) in dry dichloromethane (5 mL) was added
dropwise to a mixture of the amine 28 (0.402 g, 1.51 mmol), anhy-
drous potassium carbonate (2.08 g, 15.1 mmol), and dry silica gel
(0.40 g, Merck 60, 230–400 mesh) in dry dichloromethane (15 mL)
over 15 min and the mixture was stirred at room temperature, in the
dark, for 12 h. The reaction mixture was filtered through Celite and
the residue washed with dichloromethane (3 × 25 mL). The filtrate was
washed with water (2 × 20 mL), then saturated sodium bicarbonate
solution (2 × 20 mL), dried, and evaporated to yield an oil that was
chromatographed sequentially on two flash columns. The first col-
umn (methanol/dichloromethane, 5 : 95) removed selenium-containing
byproducts, while the second, using chloroform/acetone (98 : 2), yielded
the title compound as a pale yellow oil (0.315 g, 66%) (Found: 353.0198.
C15H16 35ClN3 77Se requires 353.0187). νmax (CH2Cl2)/cm−1 3275,
1600, 1500. δH 7.48 (2H, m, ArSe), 7.30 (1H, s, ArH), 7.20 (3H, m,
ArSe), 4.34 (1H, br s, NH), 4.27 (1H, dd, Jax 2, Jbx 8, CHxCHaHb),
3.21 (1H, dd, Jab 13, Jbx 8, CHxCHaHb), 3.08 (1H, dd, Jax 2, Jab 13,
2-Chloro-4-(1,1-dimethyl-2-propyn-1-ylamino)pyrimidine 24 was
obtained in the following way. Tetrabutylammonium fluoride (1 M,
0.43 mL, 0.43 mmol) was added to a solution of 22 (108 mg, 0.40 mmol)
in tetrahydrofuran (10 mL) and the mixture was stirred at room temper-
ature overnight. Dichloromethane (10 mL) was added and the solution
was extracted with water. The combined organic extracts were dried
and the solvent was removed to give a yellow solid that was recrystal-
lized from ethanol/water to give the amine as colourless needles (61 mg,
77%), mp 90–91◦C (Found: C 55.0, H 5.2, N 21.8; M – H 194.0490.
C9H10ClN3 requires C 55.2, H 5.2, N 21.5%; M – H 194.0485). νmax
(CH2Cl2)/cm−1 3292, 3128, 1651, 1588, 1500. δH 8.11 (1H, d, J 6.0,
ArH), 6.75 (1H, d, J 6.0), 5.42 (1H, br s, NH), 2.43 (1H, s, alkyne H),
1.63 (6H, s, CMe). m/z 194/196 (96%, M – H), 180/182 (100), 160 (38).
2-Chloro-4-(1,1-dimethyl-2-propen-1-ylamino)pyrimidine 25 was
obtained in the following way. The alkyne 24 (195 mg) in ether
(10 mL) was stirred with a Lindlar catalyst (20 mg) under an atmo-
sphere of hydrogen until 1.1 mmol of hydrogen had been absorbed.
After the usual workup, the solution was filtered through Celite and

374
M. A. Holman, N. M. Williamson and A. D. Ward
CHxCHaHb), 1.46 (3H, s, Me), 1.24 (3H, s, Me). m/z 351/353/355/357
(65%, M), 276/278/280/282 (100).
Acknowledgments
M.A.H. thanks the University of Adelaide for the award of a
Postgraduate Scholarship. N.M.W. acknowledges, with grat-
itude, the assistance of an Australian Postgraduate Research
Award (Priority).
2-Chloro-7,7-dimethyl-5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine
30 was obtained in the following way. The selenide 29 (20 mg,
0.06 mmol) was dissolved in tetrahydrofuran (2 mL), butyllithium (2 M,
60 µL, 0.12 mmol) was added to the solution at room temperature, and
the mixture was stirred for 30 min. Water was then added, the mix-
ture was stirred for 15 min, and then extracted with dichloromethane
(3 × 10 mL). The combined organic extracts were washed with satu-
rated sodium bicarbonate solution (2 × 10 mL), dried, and the solvent
was removed under reduced pressure.The residue was chromatographed
(dichloromethane/methanol) to yield the reduction product as a pale yel-
low oil (6 mg, 54%) (Found: 197.0706. C9H12ClN3 requires 197.0720).
νmax (CH2Cl2)/cm−1 3266. δH 7.36 (1H, s, ArH), 5.44 (1H, br s, NH),
3.58 (2H, t, J 7.0, CH2), 2.85 (2H, t, J 7.0, CH2), 1.29 (6H, s, Me). m/z
197/199 (28%, M), 182/184 (100).
2-Chloro-7,7-dimethyl-7,8-dihydropyrido[2,3-d]pyrimidine 31 was
obtained in the following way. A solution of sodium periodate (50 mg,
0.22 mmol) in water (1 mL) was added dropwise to a solution of
the selenide 29 (35 mg, 0.1 mmol) in methanol (3.5 mL) and water
(1.5 mL) at 0◦C. The mixture was allowed to warm to room tem-
perature and then stirred overnight. The mixture was filtered, the
precipitate washed with methanol (2 × 3 mL), and the filtrate concen-
trated. Dichloromethane was added to the residue, and the solution was
washed with water (2 × 5 mL), then dried, and the solvent evaporated.
The residue was chromatographed (methanol/dichloromethane, 2 : 98)
to afford the title compound as a colourless oil (3.4 mg, 18%) (Found:
195.0571. C9H10ClN3 requires 195.0563). νmax (CH2Cl2)/cm−1 3281,
1620. δH [(CD3)2O] 7.55 (1H, s, ArH), 7.04 (1H, d, J 8.0, CH=CH),
5.22 (1H, d, J 8.0, CH=CH), 2.93 (1H, br s, NH), 1.49 (6H, s, Me). m/z
195/197 (76%, M), 180/182 (100).
References
[1] N. M. Williamson, A. D. Ward, Tetrahedron 2005, 61, 155.
doi:10.1016/J.TET.2004.10.035
[2] M. A. Cooper, M. A. Lucas, J. M. Taylor, A. D. Ward,
N. M. Williamson, Synthesis 2001, 621. doi:10.1055/S-2001-
12349
[3] C. L. Francis, N. M. Williamson, A. D. Ward, Synthesis 2004,
2685. doi:10.1055/S-2004-831234
[4] G. F. Hennion, A. P. Boisselle, J. Org. Chem. 1961, 26, 725.
[5] N. R. Easton, G. F. Hennion, Chem. Abstr. 1967, 67, 99627.
[6] S. R. Landor, A. N. Patel, P. F. Whiter, P. M. Greaves, J. Chem.
Soc. C 1966, 1223. doi:10.1039/J39660001223
[7] A. M. Caporusso, R. Geri, C. Polizzi, L. Lardicci, Tetrahedron
Lett. 1991, 32, 7471. doi:10.1016/0040-4039(91)80138-V
[8] E. R. T. Tiekink, unpublished.
[9] L. M. Harwood, Aldrichim. Acta 1985, 18, 25.
[10] F. Kaplan, H. Conroy, J. Org. Chem. 1963, 28, 1593.
[11] I. B. Mahadevan, M. C. Kimber, S. F. Lincoln, E. R. T. Tiekink,
A. D. Ward, W. H. Betts, I. J. Forbes, P. D. Zalewski,Aust. J. Chem.
1996, 49, 561.
[12] Aldrich Library of 13C and 1H FT NMR Spectra (Eds
C. J. Pouchert, J. Behnke) 1993,Vol. 3, p. 422C (Aldrich Chemical
Co.: St. Louis, MO).
This compound was also made (17%) using hydrogen peroxide
(30%) as the oxidant.
[13] N. Whittaker, J. Chem. Soc. 1953, 1646.