Thermal cyclization of phenylallenes that contain ortho-1,3-dioxolan-2-yl groups: New cascade reactions initiated by 1,5-hydride shifts of acetalic hatoms

Article abstract of DOI:10.1002/chem.201301608

A series of 2-(1,3-dioxolan-2-yl)phenylallenes that contained a range of substituents (alkyl, aryl, phosphinyl, alkoxycarbonyl, sulfonyl) at the cumulenic C3 position were prepared by using a diverse range of synthetic strategies and converted into their respective 1-(2-hydroxy)-ethoxy-2- substituted naphthalenes by smooth thermal activation in toluene solution. Electron-withdrawing groups at the C3 position accelerated these tandem processes, which consisted of 1)an initial hydride-like [1,5]-H shift of the acetalic Hatom onto the central cumulene carbon atom; 2)a subsequent 6π-electrocyclic ring-closure of the resulting reactive ortho-xylylenes; and 3)a final aromatization step with concomitant ring-opening of the 1,3-dioxolane fragment. If the 1,3-dioxolane ring of the starting allenes was replaced by a dimethoxymethyl group, the reactions led to mixtures of two disubstituted naphthalenes, which were formed by the migration of either the acetalic Hatom or the methoxy group, with the latter migration occurring to a lesser extent. Two of the final 1,2-disubstituted naphthalenes were converted into their corresponding naphtho-fused dioxaphosphepine or dioxepinone through an intramolecular transesterification reaction. A DFT computational study accounted for the beneficial influence of the 1,3-dioxolane fragment on the carbon atom from which the H-shift took place and also of the electron-withdrawing substituents on the allene terminus. Remarkably, in the processes that contained a sulfonyl substituent, the conrotatory 6π-electrocyclization step was of lower activation energy than the alternative disrotatory mode.

Full text of DOI:10.1002/chem.201301608

FULL PAPER
DOI: 10.1002/chem.201301608
Thermal Cyclization of Phenylallenes That Contain ortho-1,3-Dioxolan-2-yl
Groups: New Cascade Reactions Initiated by 1,5-Hydride Shifts
of Acetalic H Atoms
Mateo Alajarin,*[a] Baltasar Bonillo,[a] Marta Marin-Luna,[a]
Pilar Sanchez-Andrada,*[b] and Angel Vidal*[a]
Dedicated to Professor Rosa M. Claramunt on the occasion of her 65th birthday
Abstract: A series of 2-(1,3-dioxolan-2-
yl)phenylallenes that contained a range
of substituents (alkyl, aryl, phosphinyl,
alkoxycarbonyl, sulfonyl) at the cumu-
lenic C3 position were prepared by
using a diverse range of synthetic strat-
egies and converted into their respec-
tive 1-(2-hydroxy)-ethoxy-2-substituted
naphthalenes by smooth thermal acti-
vation in toluene solution. Electron-
withdrawing groups at the C3 position
accelerated these tandem processes,
which consisted of 1) an initial hydride-
like [1,5]-H shift of the acetalic H atom
onto the central cumulene carbon
atom; 2) a subsequent 6p-electrocyclic
ring-closure of the resulting reactive
ortho-xylylenes; and 3) a final aromati-
zation step with concomitant ring-
opening of the 1,3-dioxolane fragment.
If the 1,3-dioxolane ring of the starting
allenes was replaced by a dimethoxy-
methyl group, the reactions led to mix-
tures of two disubstituted naphtha-
lenes, which were formed by the migra-
tion of either the acetalic H atom or
the methoxy group, with the latter mi-
gration occurring to a lesser extent.
Two of the final 1,2-disubstituted naph-
thalenes were converted into their cor-
responding naphtho-fused dioxaphos-
phepine or dioxepinone through an in-
tramolecular transesterification reac-
tion. A DFT computational study ac-
counted for the beneficial influence of
the 1,3-dioxolane fragment on the
carbon atom from which the H-shift
took place and also of the electron-
withdrawing substituents on the allene
terminus. Remarkably, in the processes
that contained a sulfonyl substituent,
the conrotatory 6p-electrocyclization
step was of lower activation energy
than the alternative disrotatory mode.
Keywords: allenes
density functional calculations
·
cyclization
·
·
naphthalenes · substituent effects
Introduction
D derivatives (Scheme 1a).[5] Okamura and co-workers have
heavily studied the thermally induced [1,5]-H shifts that
occur in conjugated vinylallenes, which give rise to conjugat-
ed hexatrienes that may further undergo 6p-electrocyclic
ring-closure (6p-ERC), thus yielding cyclohexadienes.[5,6] If
the vinylic double bond of the vinylallene framework is part
of an aromatic ring, the reaction products of the [1,5]-H/6p-
ERC sequence are dihydronaphthalenes. In fact, Hansen,
Schmidt, and co-workers[7] in the seventies and Grimme,
Roth, and co-workers[8] in the nineties reported that, at 150–
1908C, mesitylallenes underwent a [1,5]-H shift to afford
ortho-quinodimethane intermediates, which, under the ther-
mal reaction conditions, exhibited ring-closure to give 1,2-di-
hydronaphthalenes (Scheme 1b). Recently, Gu and Ma re-
ported a tandem [1,5-H]-shift/6p-ERC process in 4-allenyl-
5H-furan-2-ones that contained a vinylallene substructure
(Scheme 1c).[9]
Allenes[1] have the ability to participate in a range of pericy-
clic processes, such as intermolecular and intramolecular
[m+n] cycloaddition reactions,[2] Alder-ene reactions,[3] and
[1,n]-H shifts.[4] Among the different modes of sigmatropic
migration of a hydrogen atom to the cumulenic central
carbon atom of an allenic unit, [1,5]-H rearrangements are
by far the most studied. As a matter of fact, this class of pro-
cesses occur in important transformations of vitamin A and
[a] Prof. M. Alajarin, Dr. B. Bonillo, M. Marin-Luna, Prof. A. Vidal
Departamento de Quꢀmica Orgꢁnica
Universidad de Murcia, Facultad de Quꢀmica
Regional Campus of International Excellence
“Campus Mare Nostrum”, Espinardo, 30100 Murcia (Spain)
E-mail: alajarin@um.es
vidal@um.es
We have recently reported several experimental and com-
putational studies on [1,5]-H shifts in some classes of acetal-
ketenimines (Y=CR1R2) and acetal-carbodiimides (Y=
NAr), in which the acetalic function was shown to facilitate
the migration of its H atom onto the central electrophilic
carbon atom of the heterocumulenic fragment.[10] These re-
arrangements were computationally scrutinized in detail
[b] Dr. P. Sanchez-Andrada
University Centre of Defense at the Spanish Air Force Academy
Base Aerea de San Javier, C/Coronel Lopez PeÇa s/n
30720, Santiago de la Ribera, Murcia (Spain)
E-mail: pilar.sanchez@cud.upct.es
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201301608.
Chem. Eur. J. 2013, 19, 16093 – 16103
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
16093

Results and Discussion
This transformation was first assayed with allenes of general
structure 3, which contained a 1,3-dioxolane moiety as a po-
tential hydride donor group. Compounds 3 were prepared
from propargylic alcohols 2, which themselves were pre-
pared in excellent yields by the addition of ethynylmagnesi-
um bromide or phenylethynylmagnesium bromide to 2-(1,3-
dioxolan-2-yl)benzaldehydes 1. The conversion of alcohols 2
into allenes 3, in which R3 is an alkyl group, was carried out
by following a two-step sequence that consisted of the treat-
ment of compounds 2 with methyl chloroformate in the
presence of pyridine and a subsequent copper-mediated SN2’
substitution reaction of the resulting propargylic carbonates
by alkylmagnesium cuprates. The direct coupling of propar-
gylic alcohol 2a with arylboronic acids, under palladium cat-
alysis, produced 1,3-disubstituted allenes 3, in which R3 is an
aryl group. The reaction of alcohols 2 with chloroaryl phos-
phines and diethyl chlorophosphite in the presence of pyri-
dine afforded allenylic diaryl phosphine oxides (3, R3 =
(O)PAr2) and allenylic phosphonic acid diethyl esters (3,
Scheme 1. a) [1,5]-H shift in the vinylallene fragment of vitamin D.
b,c) Tandem [1,5]-H shift/6p-ERC processes in mesitylallenes (b) and in
b-allenylfuranones (c).
R3 =(O)P
ACHTNUTRGNE(UNG OEt)2). Heating solutions of 1,3-dioxolane-allenes
3 in toluene at reflux, or at 150–1608C in a sealed tube, af-
forded spironaphthalenes 4 or, in most of the studied cases,
1-(2-hydroxy)ethoxy-2-substituted naphthalenes 5, which
were isolated in acceptable yields (Scheme 3, Table 1).
Under the applied thermal conditions (toluene, 1608C,
sealed tube, 48 h), the reaction of allene 3l (R1 =H, R2 =
and, as a consequence, were chemically interpreted as hy-
dride shifts. The reactive ortho-azaxylylene intermediates
that resulted from these rearrangements rapidly underwent
6p-ERC, thereby finally furnishing substituted quinolines
(Y=CR1R2) and quinazolines (Y=NAr, Scheme 2).
C6H5, R3 =C
ture, from which we were only able to isolate 7,12-
ACHTUGNERTN(NUNG CH3)3) provided a very complex reaction mix-
dihydrodibenzoACTHNUTRGNEUNG[a,d]cyclooctene 6l (Scheme 3), albeit in
very low yield (10%). Spirocycles 4, in which R2 =H, are
Scheme 2. Previously studied tandem processes in acetal-ketenimines and
acetal-carbodiimides.
Based on the results of these tandem processes and taking
into account that allenes are prone to participating in [1,5]-
H shifts, we reasoned that the central carbon atom of an
allene function might also act as the terminus of a [1,5]-H
shift, with its origin at an adequately placed acetalic carbon
atom. Thus, herein, we report a new type of intramolecular
ꢀ
carbon carbon bond formation that is triggered by an initial
[1,5]-H shift, in which the H atom departs from the acetalic
carbon atom of a 1,3-dioxolane ring that is at the ortho posi-
tion of a phenylallene moiety. This new tandem process has
also been studied in substrates that contained non-cyclic
acetalic and ether functions as the hydride donors. We will
show that, in these latter classes of substrates, the migration
of alkoxy groups competes with that of the respective ben-
zylic hydrogen atoms.
2
ꢁ
Scheme 3. Reagents and conditions: a) R C CMgBr, THF, 08C, 40 min.
b) For R3 =alkyl: (i) ClCO2CH3, pyridine, CH2Cl2, 08C, 1 h; (ii) R3MgBr,
CuI, LiBr, THF, 08C, 40 min. For R3 =aryl: ArB(OH)2, [Pd
ACHTUNTRGNEUNG(PPh3)4], 1,4-
dioxane, 908C, 15 min. For R3 =(O)PR2: ClPR2, pyridine, CH2Cl2/Et2O,
08C!RT, 10 h. c) For compounds 4b, 5a, and 6l: toluene, 150–1608C,
sealed tube, 30–72 h. For compounds 5c–k,m,n: toluene, reflux, 3–48 h.
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Cyclization of ortho-1,3-Dioxolan-2-yl-Substituted Phenylallenes
Table 1. Synthesis of allenes 3, spironaphthalenes 4, and naphthalenes 5.
FULL PAPER
To assess our mechanistic interpretation, we carried out
a deuterium-labeling experiment. Monodeuterated com-
pound [D]1a, which was easily prepared from formyl-deu-
terated 2-bromobenzaldehyde[13] by acetalization/formyla-
tion (see the Supporting Information), was submitted to the
whole reaction sequence, thereby affording naphthalene
Entry
R1
R2
R3
Yield
Yield [%]
[%] 3
4, 5, or 6
1
2
3
4
5
6
7
8
H
H
H
H
H
H
H
H
OCH3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C6H5
C6H5
C6H5
CH3
CACHTNGUTRENNU(G CH3)3
C6H5
2-CH3-C6H4
3-CH3-C6H4
4-CH3-C6H4
4-CH3O-C6H4
(O)P
(O)P
47 (3a)
88 (3b)
48 (3c)
30 (3d)
41 (3e)
31 (3 f)
44 (3g)
68 (3h)
43 (3i)
25 (3j)
81 (3k)
75 (3l)
70 (3m)
20 (3n)
30 (5a)
50 (4b)
70 (5c)
78 (5d)
57 (5e)
58 (5 f)
65 (5g)
80 (5h)
89 (5i)
60 (5j)
93 (5k)
10 (6l)
79 (4m)
65 (4n)
1
[D]5h (Scheme 5). As expected, the H NMR spectrum of
ACHTUNGTRENNUNG
9
ACHTUNGTRENNUNG
10
11
12
13
14
(O)P(2-CH3-C6H4)2
(O)P(OEt)2
(CH3)3
ACHTUNGTRENNUNG
CACHTUNGTRENNUNG
(O)P
(O)P
ACHTUNGTRENNUNG
H
ACHTUNGTRENNUNG
converted in situ into 1-(2-hydroxy)ethoxynaphthalenes 5
through a formal b-elimination process that results in the
opening of the dioxolane ring, which is energetically favored
owing to the resultant gain in aromatic stability. For some
reason, presumably related to the bulkiness of the tert-butyl
ꢁ
Scheme 5. Reagents and conditions: a) HC CMgBr, THF, 08C, 40 min.
group, compound 4b (R1 =R2 =H, R3 =C
ACTHUNGTRNEUNG(CH3)3) did not
b) ClP
4 h.
A
undergo this latter step.
The lowest yield was obtained with methyl-substituted
allene 3a (R3 =CH3), which may be due to the availability
of the methyl H atoms for alternative reaction pathways.[11]
For this reason, other allenes that contained alkyl groups at
their terminal C atom and, hence, could potentially undergo
similar rearrangements, were excluded from our study. Fur-
thermore, Table 1 shows that the highest yields of the 3!4/5
conversion reactions correspond to cases in which the allene
fragment is substituted by electron-withdrawing groups, such
as Ar2P(O) and (EtO)2P(O). This activation effect is in
accord with the presumed electronic bias of the rate-deter-
mining [1,5]-H shift, which is the migration of a hydride
onto an electrophilic sp-hybridized carbon atom.
The formation of dibenzocyclooctene 6l can be rational-
ized as resulting from an initial 1,5-hydride shift that leads
to ortho-xylylene 7. Further cyclization of this reactive inter-
mediate through an 8p-electrocyclic ring-closure pathway,[12]
followed by a prototropic equilibration, finally leads to com-
pound 6l (Scheme 4). The alternative 6p-electrocyclization
step, which was initially presumed, was apparently prevent-
ed by the severe steric congestion that was caused by the
phenyl and tert-butyl substituents at one end of the hexa-
triene system.
compound [D]5h, on comparison with that of non-deuterat-
ed compound 5h, showed the apparent complete disappear-
ance of the 1H doublet of doublet at d=6.91 ppm, which
was attributed to the H3 proton of the naphthalene nucleus
of compound 5h and was coupled to the H4 proton (3J-
ACHUTNGRENNUG ACHTUNGTRENNUNG(H,P)=
(H,H)=8.4 Hz) and to the phosphorus atom (3J
12.0 Hz). The remaining spectroscopic data of compound
[D]5h were in accord with its indicated structure (see the
Experimental Section and the Supporting Information).
Next, we investigated the application of this tandem pro-
cess to related allenes that contained various electron-with-
drawing substituents on their terminal carbon atom. With
this aim in mind and taking into account the fact that allenes
can be readily obtained by the base-catalyzed isomerization
of alkynes,[3c,14] we prepared propargylic sulfone 8 and 3-al-
kynoates 13 as potential precursors of new allenes for use in
our tandem sequences. The reaction of alcohol 2a with 4-ni-
trophenylsulfenyl chloride and triethylamine led to the for-
mation of a sulfoxide that was immediately oxidized with
meta-chloroperbenzoic acid into propargylic sulfone 8. The
coupling reaction between phenylacetylenes 12, which were
prepared by the treatment of 2-ethynylbenzaldehyde 11 with
1,2-propanediol and 1,3-propanediol under catalysis by
para-toluenesulfonic acid, and ethyl and tert-butyl diazoace-
tate in the presence of copper iodide gave new 3-alkynoates
13. Exposing compounds 8 and 13 to a catalytic amount of
triethylamine at reflux in toluene allowed for the formation
of an equilibrium mixture of allenes 9 and 14, which, under
such reaction conditions, underwent the tandem 1,5-hydride
shift/6p-electrocyclization/b-elimination process to furnish
moderate-to-good yields of the corresponding 2-sulfonyl-
Scheme 4. Proposed mechanism for the formation of dibenzocyclooctene
6l.
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M. Alajarin, P. Sanchez-Andrada, A. Vidal et al.
Scheme 6. Reagents and conditions: a) (i) 4-NO2-ClSC6H4, Et3N, THF,
Scheme 7. Reagents and conditions: a) N2=CHCOOR, CuI, MeCN, RT,
ꢀ788C, 1 h; (ii) m-CPBA, CH2Cl2/NaHCO3 (sat.), 08C, 1 h. b) Toluene,
10 h. b) Toluene, Et3N (cat.), reflux, 4 h.
Et3N (cat.), reflux, 4–5 h. c) HOACTHUNTGRENUNG(CH2)nCH2OH, p-TsOH (cat.), benzene,
reflux, 4 h. d) N2=CHCOOR, CuI, MeCN, RT, 10 h. m-CPBA=meta-
chloroperoxybenzoic acid.
final aromatization by the elimination of MeOH. These re-
sults show that, as expected, the replacement of the cyclic
acetal group in our acetalic allenes by an acyclic one, as in
allenes 18, makes the migration of the alkoxy units of the
acyclic acetal possible. However, the hydride shift is still the
predominant anionotropic rearrangement, despite its 1:2
statistical disadvantage.
and alkoxycarbonyl-substituted 1-(2-hydroxy)ethoxynaph-
thalenes (10 and 15, respectively; Scheme 6).
Our next investigation into these tandem processes that
were based on the internal transfer of a hydrogen atom as
a hydride onto the central carbon atom of an allene moiety
relied on the utilization of substrates that contained non-
cyclic acetalic and ether groups at the benzylic positions as
potential hydride-releasing fragments. By using this type of
substrates, we anticipated that the migration of an alkoxy
group could effectively compete with the migration of the
hydrogen atom, as suggested by some related results.[15]
The copper-catalyzed coupling reactions of 1-(dimethoxy-
methyl)-2-ethynylbenzene 16 with ethyl and tert-butyl diazo-
acetate provided the corresponding 3-alkynoates (17). The
heating of solutions of compounds 17 in toluene with a cata-
lytic amount of triethylamine promoted their conversion
into mixtures of the alkyl (1-methoxy) and (3-methoxy)-2-
naphthoates (21 and 24, respectively); in all cases, the 1,2-
disubstituted regioisomers (21) were the major reaction
products (Scheme 7).
Next, we tested the inverse statistical situation, that is,
two benzylic hydrogen atoms versus only one alkoxy group
on the same carbon atom. With the above results in hand,
we expected the exclusive migration of the hydride in this
case. Thus, by using 2-(methoxymethyl)benzaldehyde (25) as
the starting material according to the synthetic sequence
shown in Scheme 8, we attempted the preparation of 1,3-dis-
ubstituted allene derivative 27, which contained an ether
group at the ortho position. Allene 27 could only be con-
verted into cis-2-(tert-butyl)-1-methoxy-1,2-dihydronaphtha-
lene 28 (Scheme 8) under dramatic thermal activation, that
is, heating its solution in toluene at 1508C in a sealed tube
for 50 h;[16] compound 28 was the only reaction product that
we could isolate by column chromatography from a very
complex reaction mixture. Compound 28 was the result of
a typical tandem process that was initiated by a [1,5]-H
shift, but lacked the final formal b-elimination step, as in the
case of the structurally related tert-butyl-substituted com-
pound 4b (cited above).
As summarized in Scheme 7, the two reaction channels in-
volve the [1,5]-shift of either the acetalic H atom or one of
the methoxy groups on the benzylic carbon atom, thereby
leading to major and minor regioisomers 21 and 24, respec-
tively, following a subsequent 6p-electrocyclization step and
Several of the disubstituted naphthalenes that were pre-
pared above contained a 1-(2-hydroxy)ethoxy substituent at
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Cyclization of ortho-1,3-Dioxolan-2-yl-Substituted Phenylallenes
FULL PAPER
ꢁ
Scheme 8. Reagents and conditions: a) HC CMgBr, THF, 08C, 40 min.
b) (i) ClCO2CH3, pyridine, CH2Cl2, 08C, 1 h; (ii) (CH3)3CMgBr, CuI,
LiBr, THF, 08C, 40 min. c) Toluene, 1508C, sealed tube, 50 h.
the C1 carbon atom of the naphthalene ring and phosphonic
or carboxylic-ester groups at the C2 position. This combina-
tion of structural fragments allowed us to investigate intra-
molecular transesterification reactions for the conversion of
these compounds into their corresponding macrocyclic
esters. As expected, the treatment of compounds 5k and
15a with sodium hydride achieved their conversion into
naphthalene-fused 1,5,2-dioxaphosphepin 29 and 1,4-dioxe-
pin-5-one 30, respectively (Scheme 9).
Scheme 10. Computed pathways for the conversion of 1,3-dioxolane-al-
lenes 31a–31d into spironaphthalenes 32a–32d.
Scheme 11. Computed pathways for the conversion of 2-tolylallene (33)
into 1,2-dihydronaphthalene (34).
Scheme 9. Reagents and conditions: a) NaH, THF, RT, 5 h.
We have also carried out a brief DFT computational
study at the B3LYP/6-31+G** level of theory of the
tandem [1,5]-H-shift/6p-electrocyclization processes for the
conversion of a series of allenes (31a–31d) into their corre-
sponding spirodihydronaphthalenes (32a–32d, Scheme 10).
Allenes 31b–31d, which contained either terminal alkyl,
aryl, or electron-withdrawing substituents (Me, Ph, SO2H),
were chosen as representative models of the compounds
that were utilized in the experimental study;[17] the unsubsti-
tuted allene (31a) was also chosen for the sake of compari-
son with the rest of allenes to determine the effects of the
substituents. Moreover, we also computed the conversion of
the analogous non-acetalic allene 33 into dihydronaphtha-
lene 34, with the aim of confirming the activating effect of
the acetalic group on the carbon atom, which was the origin
of the H-shift (Scheme 11).
Table 2. As shown in Scheme 10, whereas only one inter-
mediate, INTa, resulted from an initial [1,5]-H shift in allene
31a, which contained no substituents at the allene terminus,
in the cases of X-substituted allenes 31b–31d, this first step
might lead to the diastereoisomeric cis or trans ortho-quino-
dimethanes, INTcis or INTtrans, through their respective tran-
sition structures (TS1) over the corresponding energy barri-
¼
ers (DE1 ). Each of these INT intermediates can electro-
cyclize into their respective final spirocycle (32) through two
alternative transition structures, that is, TS2dis and TS2con, as
result of the two rotatory modes, disrotatory and conrotato-
¼
¼
ry, with the respective energy barriers of DE2
and DE2
dis
con, respectively. Table 2 also shows the differences in energy
between the starting allenes (31) and the reaction intermedi-
ates (INT), denoted as DEINT, as well as the relative reaction
energies of the whole processes, DErxn
By comparing the DE1 values in Table 2, entries 1 and 8,
.
¼
The computed energy barriers and reaction energies for
the processes shown in Schemes 10 and 11 are listed in
it is clear that the 1,3-dioxolane group plays an activating
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M. Alajarin, P. Sanchez-Andrada, A. Vidal et al.
Table 2. Energy barriers and reaction energies [kcalmolꢀ1] for the conversions of allenes 31a–31d and 33 into
their respective naphthalenes (32a–32d and 34), computed at the B3LYP/6-31+G**+DZPVE level of theory.
For X-substituted allenes
31b–31d, the energy barriers
for the reaction pathways that
lead to the trans intermediates
(INTtrans) are, in all cases, lower
than those of the alternative
pathways that lead to the cis in-
¼
¼
Conversion
X
H
DE1
DEINT
DE2
DErxn
ꢀ31.5
¼
¼
¼
¼
¼
¼
¼
¼
¼
¼
¼
¼
¼
¼
¼
¼
31a!INTa!32a
28.6
4.0
18.0 (DE2
28.4 (DE2
30.2 (DE2
33.2 (DE2
18.3 (DE2
31.9 (DE2
25.6 (DE2
26.9 (DE2
17.5 (DE2
24.2 (DE2
23.9 (DE2
22.3 (DE2
16.6 (DE2
13.7 (DE2
15.2 (DE2
34.6 (DE2
)
dis
)
con
¼
¼
¼
¼
¼
¼
31b!INTbcis!32b
31b!INTbtrans!32b
31c!INTccis!32c
31c!INTctrans!32c
31d!INTdcis!32d
31d!INTdtrans!32d
33!INT33!34
Me
28.7 (DE1
28.5 (DE1
26.0 (DE1
24.4 (DE1
22.2 (DE1
19.3 (DE1
33.6
)
4.4 (DEINTcis
)
)
cisdis
ꢀ28.8
ꢀ28.8
ꢀ25.2
ꢀ25.2
ꢀ31.3
ꢀ31.3
ꢀ27.7
cis
)
ciscon
Me
)
)
)
3.3 (DEINTtrans
6.2 (DEINTcis
1.2 (DEINTtrans
0.5 (DEINTcis
)
)
)
transdis
trans
termediates (INTcis
;
compare
and DE1
)
)
)
transcon
¼
¼
Ph
)
)
)
the values of DE1
cis
cisdis
cis
)
ciscon
in Table 2, entry 2 vs.
trans
Ph
)
trans
transdis
entry 3, entry 4 vs. entry 5, and
entry 6 vs. entry 7). This trend
can be interpreted on the basis
of the larger degree of steric
over-crowding in the TS1cis
transition structures compared
with that in their diastereoiso-
meric TS1trans transition struc-
tures. Thus, there is a clear
transcon
S(=O)2H
S(=O)2H
H
)
)
)
cis
cisdis
)
ciscon
ꢀ5.3 (DEINTtrans
12.8 (DEINT35
)
)
trans
transdis
transcon
)
)
dis
)
con
role by decreasing the energy barrier of the first step, that is,
preference for the syn trajectories, which lead to INTtrans, in
¼
the H-shift, by DDE1 =5 kcalmolꢀ1, whilst at the same time
all of the cases studied here. The difference between the
¼
making this step considerably less endergonic by 8.8 kcal
DDE1 values for the activation energies of the syn and anti
molꢀ1.
trajectories (which lead to the respective trans and cis INT
intermediates) increases on going from X=Me (0.2 kcal
molꢀ1) to X=Ph (1.6 kcalmolꢀ1) and X=SO2H (2.9 kcal
molꢀ1). Analogously, as expected, the DEINTtrans values were
lower than the DEINTcis values (Table 2, entries 2–7). In all
cases, the first step in the tandem process was calculated to
be an endergonic reaction, with the only exception of the
transformation shown in Table 2, entry 7.
In terms of the electronic effects of the X substituents, the
presence of a methyl group practically did not change the
¼
computed DE1 energy barrier of the first step (Table 2,
entry 1 vs. entries 2 and 3). In contrast, both phenyl and sul-
fonyl groups (Table 2, entries 4–7) significantly decreased
¼
the DE1 energy barriers, an effect that was more notable in
the case of the SO2H substituent. Such an effect may be at-
tributed to an enhancement of the electrophilicity of the
allene fragment, which correlated with the hydride-like char-
acteristics of the migrating H atom.
These [1,5]-H shifts take place in a suprafacial manner
and, for X-substituted allenes, the hydrogen migration can
follow syn or anti trajectories with respect to the X substitu-
ent. The syn trajectory occurs through transition structures
Concerning the second step, that is, the 6p-electrocyclic
ring-closure of the INT intermediates into the final spirocy-
cles (32 and 34), the data in Table 2 show that most of the
intermediates can undergo the transformation through at
¼
least one reaction pathway, which has a smaller DE2 barri-
¼
er than the respective DE1 barrier. Thus, we can conclude
that, as a general trend, the first step in the tandem process,
that is, the hydride shift, is the slowest one. The subsequent
electrocyclization was calculated to be a highly exergonic
step, most probably as a consequence of the recovery of aro-
maticity at the benzene ring.
TS1btrans–TS1dtrans, thus leading to intermediates INTbtrans
–
INTdtrans, whereas the anti trajectory occurs through transi-
tion structures TS1bcis–TS1dcis, thus leading to intermediates
INTbcis–INTdcis (Scheme 12).
We located two transition structures in the electrocycliza-
tion reactions of each intermediate (INTa–INTd), which cor-
responded to the two rotatory modes, conrotatory and disro-
tatory, denoted as TS2acon–TS2dcon and TS2adis–TS2ddis, re-
spectively. Their geometries are shown in Figure 1. The tran-
sition structures that corresponded to the disrotatory path-
ways showed the archetypal boat-like conformation of the
forming six-membered ring, in which the bonds at the C1
and C6 positions were practically eclipsed (Figure 1B). In
contrast, the transition structures that corresponded to the
conrotatory pathways showed a skewed half-chair conforma-
tion, with alternated bonds at the C1 and C6 positions (Fig-
ure 1B). Notably, the transition structures for the cyclization
of the X-substituted cis intermediates, INTbcis–INTdcis,
through any of the two rotatory modes showed the X sub-
stituent was oriented inwards, whereas, in all cases, the tran-
Scheme 12. Syn- and anti-trajectories for the suprafacial [1,5]-H shifts in
allenes 31b–31d.
16098
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Chem. Eur. J. 2013, 19, 16093 – 16103

Cyclization of ortho-1,3-Dioxolan-2-yl-Substituted Phenylallenes
FULL PAPER
¼
tailed inspection of the calculated DE2 energy barriers in
Table 2 shed some light on the reasons for these two anoma-
lous cases of preference for the conrotatory mode.
As stated above for Table 2, entries 6 and 7, the differen-
¼
ces between the DE2 values of the disrotatory and conrota-
tory cyclization modes of each INT are higher for the the
INTtrans intermediates than for their INTcis counterparts (cf.
¼
the differences in DDE2 between entries 4 and 5 and be-
tween entries 2 and 3). Thus, it seems that the higher steric
buttressing of transition structures TS2cis, which correspond
to the cyclization of the cis intermediates, compared with
transition structures TS2trans, provokes a decrease in the
energy difference between the two rotatory modes, thereby
making the disrotatory modes less favored on going from
INTa to INTc and even reaching an inversion of the typical
order of preference in the case of INTd. A general trend
¼
can be extracted by analyzing the DE2 values in Table 2.
Notably, the difference between the energy barriers of the
two rotatory modes is very high in the cyclization of unsub-
¼
stituted case INT33 (DDE2 =19.4 kcalmolꢀ1); is lower but
¼
still high in the cyclization of INTa (DDE2 =10.4 kcal
molꢀ1), in which one of the carbon atoms that forms the
bond in the cyclization step is disubstituted by the dioxolane
group whereas the other one is unsubstituted; is still high
with the addition of a Me group onto the latter carbon atom
(13.6 kcalmolꢀ1 in the trans case); is lower with the addition
of a Ph group (6.7 kcalmolꢀ1 in the trans case); and becomes
inverted in the trans case of the SO2H-substituted example
(ꢀ2.9 kcalmolꢀ1). In all cases, fewer differences were found
between the more sterically congested cis isomers.
Figure 1. a) Frontal, and b) lateral representations of the four types of
the TS2 transition structures; the positions of the X substituent at the C1
position and the two oxygen atoms at the C6 position are labeled.
Thus, the steric buttressing of the TS2 structures seems to
be a crucial factor in governing the energy barriers of the
6p-electrocyclization steps, thereby narrowing the gap be-
tween the disrotatory and conrotatory modes on going from
less to highly sterically congested cases and even allowing
the inversion of the preferences that are derived from the
selection rules. In this respect, the inclusion of one terminal
carbon atom of the hexatriene fragment, C6, into the 1,3-di-
oxolane ring should introduce severe constraints, not only
through steric repulsion with the substituents on the other
sition structures that corresponded to the trans intermedi-
ates, INTbtrans–INTdtrans, placed their X group oriented out-
wards (Figure 1A).
As shown in Figure 1, in the disrotatory transition states,
there are close contacts between the two inward-facing
atoms at the C1 and C6 positions, whereas the conrotatory
transition structures better avoid steric interference between
the atoms that are bonded to both extreme carbon atoms.
As dictated by the selection rules for pericyclic reac-
tions,[18] Table 2 shows that the disrotatory modes of the 6p-
electrocyclization reactions of the intermediates (INT) have,
in general, lower activation energies than the conrotatory
modes, with the notable exception of the electrocyclization
of INTd into compound 32d (Table 2, entries 6 and 7). The
conversion through conrotatory transition state TS2dtranscon
was calculated to occur through a modest barrier of
13.7 kcalmolꢀ1, which was 2.9 kcalmolꢀ1 lower than corre-
sponding conversion through the alternative disrotatory
transition state (Table 2, entry 7, and Figure 2). In fact, this
was the anomalous result that prompted us to compute the
rest of the conrotatory reaction channels. Similarly, the
energy barrier of the conrotatory mode for the electrocycli-
zation of INTdcis was calculated to be smaller than the
energy barrier of the disrotatory mode, albeit by only
1.6 kcalmolꢀ1 (Table 2, entry 6). As discussed below, a de-
ꢀ
terminus (C1), but also through making the required C5 C6
rotation that takes place during the electrocyclization step
more difficult. This assumption seems to be supported by
¼
the difference between the DDE2 values for the two rotato-
ry modes of INT33 (19.4 kcalmolꢀ1) and those of INTa
(10.4 kcalmolꢀ1).
Typically, the selection rules, which are based on orbital
factors, favor the disrotatory mode in terminal 6p-electro-
cyclization reactions. However, it seems that this preference
diminishes as the substituents on the terminal carbon atoms
become more voluminous and may even favor the conrota-
tory mode if the steric interference is high enough. We
cannot rule out the possibility that the electronic effects of
the substituents could also contribute to the magnitude of
the energy barriers and the selectivity of these electrocyclic
processes. Obviously, this reasoning is just a working hy-
pothesis that should be scrutinized in the light of additional
Chem. Eur. J. 2013, 19, 16093 – 16103
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
16099

M. Alajarin, P. Sanchez-Andrada, A. Vidal et al.
struction
a new seven-mem-
bered ring that is fused onto
the naphthalene ring system at
ꢀ
its C1 C2 bond. DFT computa-
tional study confirmed our ini-
tial mechanistic assumptions,
the hydride-like characteriza-
tion of the H-shift step, and the
consequential activating influ-
ence of electron-withdrawing
substituents on the allene ter-
minus. Moreover, it also
showed that the differences be-
tween the energy barriers of
the conrotatory and disrotatory
modes of the 6p-electrocycliza-
tion step were modulated by
the stereoelectronic effects of
the substituents on both cycliza-
tion termini; in one case, the
conrotatory mode was calculat-
ed to have a lower activation
energy than its disrotatory
counterpart. The further devel-
opment of synthetic strategies
that are based on the promo-
tion of hydride-like H shifts by
acetalic functions are currently
underway in our laboratories.
Figure 2. Qualitative reaction profile for the conversion 31d!32d, which shows the energy barriers and the
optimized geometries of the relevant stationary points.
computations and experiments, which are beyond of the ini-
tial scope of this study.
Experimental Section
Conclusion
All of the melting points are uncorrected. IR spectra were recorded as
1
Nujol mulls or as neat samples. H NMR spectra were recorded in CDCl3
In conclusion, herein, we have demonstrated that our strat-
egy of facilitating intramolecular H-shifts by using an acetal-
ic carbon atom as the H donor, as previously used by our-
selves in related processes on acetalic heterocumulenes, also
extends to cases in which the H-receptor is a central cumu-
lenic carbon atom. Thus, we have shown that cyclic and acy-
clic acetalic functional groups that are adequately placed at
the ortho position of a phenylallene activate their acetalic H
atom for it to be transferred onto the cumulene central
carbon atom through a thermally promoted [1,5]-H shift.
These processes are followed, in three-step one-pot reac-
tions, by the 6p-electrocyclic ring-closure of the resulting
ortho-xylylenes and a final aromatization step, with b-elimi-
or CD2Cl2 at 300 or 400 MHz. 13C NMR spectra were recorded in CDCl3
or CD2Cl2 at 75 or 100 MHz. Chemical shifts are expressed in ppm, rela-
tive to SiMe4 at d=0.00 ppm for 1H nuclei, or relative to the solvent at
d=77.1 (CDCl3) or 54.0 ppm (CD2Cl2) for 13C nuclei. 31P NMR spectra
were recorded in CDCl3 or CD2Cl2 at 121.4 or 161.9 MHz, with H3PO4 as
an internal reference.
Naphthalene 24b[19] and 1,4-dioxepin-5-one 30[20] were prepared accord-
ing to literature procedures.
Preparation of spironaphthalenes 4, naphthalene 5, and dibenzocyclooc-
tene 6l: Method A: Naphthalenes 5c–k,m,n and [D]5h. A solution of
the appropriate allene 3 (1 mmol) in anhydrous toluene (15 mL) was
heated at reflux for 3–48 h. After cooling, the solvent was removed under
reduced pressure and the crude material was purified by column chroma-
tography on silica gel.
Method B: Spironaphthalene 4b, naphthalene 5a, and dibenzocyclooctene
6l. A solution of the appropriate allene 3 (1 mmol) in anhydrous toluene
(15 mL) was heated in a sealed tube at 150–1608C for 30–72 h. After
cooling, the solvent was removed under reduced pressure and the crude
material was purified by column chromatography on silica gel.
ꢀ
nation of the corresponding alcohol along the C1 C2 bond
of the as-formed naphthalene system. These cascade reac-
tions are facilitated by electron-withdrawing groups (phos-
phinyl, alkoxycarbonyl, sulfonyl) at the terminal cumulenic
carbon atom. Such an electronic effect is rationalized on the
basis of the hydride-like characteristics of the initial, rate-
determining H-shift step. In some of these cases, the final 2-
substituted 1-(2-hydroxy)ethoxynaphthalenes can be further
elaborated by intramolecular transesterification for the con-
Naphthalene 5a: Eluent for column chromatography: hexanes/EtOAc
(7:3 v/v); yield: 30%; yellow oil; 1H NMR (300 MHz, CDCl3): d=8.11
(d, J=8.4 Hz, 1H), 7.81 (d, J=8.4 Hz, 1H), 7.56 (d, J=8.4 Hz, 1H),
7.51–7.40 (m, 2H), 7.30 (d, J=8.4 Hz, 1H), 4.11–4.05 (m, 4H), 2.46 (s,
3H), 1.99 ppm (s, 1H); 13C NMR (75 MHz, CDCl3): d=151.8, 133.7,
129.4, 128.2, 128.0, 126.3, 126.1, 125.4, 124.1, 121.6, 74.5, 62.5, 16.2 ppm;
16100
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Chem. Eur. J. 2013, 19, 16093 – 16103

Cyclization of ortho-1,3-Dioxolan-2-yl-Substituted Phenylallenes
FULL PAPER
IR (neat): n˜ =3243 cmꢀ1; HRMS (ESI): m/z calcd for C13H15O2: 203.1067
[M+H]+; found: 203.1069.
Naphthalene 5i: Eluent for column chromatography: EtOAc; yield:
89%; colorless prisms; m.p. 171–1738C (hexane); 1H NMR (300 MHz,
CDCl3): d=7.76 (d, J=9.0 Hz, 1H), 7.71–7.64 (m, 4H), 7.58–7.44 (m,
7H), 7.34 (d, J=2.4 Hz, 1H), 7.25 (dd, J=9.0, 2.4 Hz, 1H), 6.77 (dd, J=
12.0, 8.1 Hz, 1H), 4.46 (t, J=3.9 Hz, 2H), 4.14 (s, 1H), 3.90 (s, 3H),
3.86 ppm (t, J=3.9 Hz, 2H); 13C NMR (75 MHz, CDCl3): d=160.1,
Spiro naphthalene 4b: Eluent for column chromatography: hexanes/
EtOAc (9:1 v/v); yield: 50%; yellow oil; 1H NMR (300 MHz, CD2Cl2):
d=7.43–7.39 (m, 1H), 7.25–7.17 (m, 2H), 7.06 (dd, J=7.2, 1.8 Hz, 1H),
6.50 (d, J=9.9 Hz, 1H), 6.05 (dd, J=9.9, 6.0 Hz, 1H), 4.24–4.21 (m, 1H),
4.11–4.04 (m, 1H), 3.96–3.90 (m, 1H), 3.76–3.68 (m, 1H), 2.37 (dd, J=
6.0, 0.9 Hz, 1H), 0.88 ppm (s, 9H); 13C NMR (75 MHz, CDCl3): d=137.8,
134.8, 131.8, 128.9, 127.6, 126.5, 123.7, 110.6, 67.1, 63.2, 52.9, 35.8,
29.2 ppm; IR (neat): n˜ =1170, 1064 cmꢀ1; HRMS (ESI): m/z calcd for
C16H21O2: 245.1530 [M+H]+; found: 245.1530.
158.2, 133.1 (d, J
(P,C)=9.8 Hz), 130.0, 128.6 (d,
11.0 Hz), 123.4 (d, J(P,C)=12.9 Hz), 121.6, 120.6 (d, J
101.4, 78.5, 62.0, 55.5 ppm; 31P NMR (121.4 MHz, CDCl3) d=31.15 ppm;
A
ACHTUNGTRENNUNG
A
J
A
JACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
IR (Nujol): n˜ =3284 cmꢀ1
; HRMS (ESI): m/z calcd for C25H24O4P:
419.1407 [M+H]+; found: 419.1413.
Naphthalene 5c: Eluent for column chromatography: hexanes/Et2O (1:1
v/v); yield: 70%; colorless oil; 1H NMR (400 MHz, CDCl3): d=8.21 (d,
J=7.6 Hz, 1H), 7.82 (d, J=7.6 Hz, 1H), 7.65–7.62 (m, 3H), 7.52–7.41 (m,
5H), 7.35–7.31 (m, 1H), 3.78 (t, J=4.4 Hz, 2H), 3.59 (t, J=4.4 Hz, 2H),
1.86 ppm (s, 1H); 13C NMR (100 MHz, CDCl3): d=151.4, 138.6, 134.4,
130.3, 129.6, 128.5, 128.4, 128.0, 127.4, 126.4, 126.3, 124.3, 122.4, 75.4,
Naphthalene 5j: Eluent for column chromatography: EtOAc; yield:
60%; colorless prisms; m.p. 207–2058C (pentane); 1H NMR (400 MHz,
CDCl3): d=8.18 (d, J=8.0 Hz, 1H), 7.88 (d, J=8.0 Hz, 1H), 7.63–7.51
(m, 3H), 7.47–7.44 (m, 2H), 7.35–7.31 (m, 2H), 7.18–7.09 (m, 4H), 6.86
(dd, J=12.4, 8.8 Hz, 1H), 4.52 (t, J=3.6 Hz, 2H), 4.38 (s, 1H), 3.89 (t,
J=3.6 Hz, 2H), 2.50 ppm (s, 6H); 13C NMR (100 MHz, CDCl3): d=
62.0 ppm; IR (neat): n˜ =3415 cmꢀ1
; HRMS (ESI): m/z calcd for
C18H17O2: 265.1223 [M+H]+; found: 265.1225.
161.7, 143.3 (d, J
(P,C)=12.8 Hz), 132.2 (d, J
129.7 (d, J(P,C)=105.9 Hz), 128.5 (d, J
127.6, 125.7 (d, J(P,C)=13.0 Hz), 124.0 (d, J
(d, JACTHUNGTRNENUG
(P,C)=100.7 Hz), 79.1, 62.0, 22.2, 22.1 ppm; 31P NMR (161.9 MHz,
A
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
Naphthalene 5d: Eluent for column chromatography: hexanes/Et2O (3:2
v/v); yield: 78%; colorless prisms; m.p. 115–1178C (pentane); 1H NMR
(300 MHz, CDCl3): d=8.23–8.21 (m, 1H), 7.91–7.88 (m, 1H), 7.68 (d, J=
8.4 Hz, 1H), 7.57–7.49 (m, 2H), 7.36–7.28 (m, 5H), 3.86–3.79 (m, 2H),
3.58 (br s, 2H), 2.24 (s, 3H), 1.57 ppm (s, 1H); 13C NMR (75 MHz,
CDCl3): d=151.5, 138.4, 136.8, 134.5, 130.4, 130.3, 130.2, 128.9, 128.4,
128.1, 127.9, 126.3, 125.8, 123.9, 122.4, 75.5, 62.1, 20.3 ppm; IR (Nujol):
n˜ =3416 cmꢀ1; HRMS (ESI): m/z calcd for C19H19O2: 279.1380 [M+H]+;
found: 279.1384.
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
CDCl3): d=37.39 ppm; IR (Nujol): n˜ =3273 cmꢀ1; HRMS (ESI): m/z
calcd for C26H26O3P: 417.1614 [M+H]+; found: 417.1618.
Naphthalene 5k: Eluent for column chromatography: EtOAc; yield:
93%; colorless oil; 1H NMR (300 MHz, CDCl3): d=8.17–8.14 (m, 1H),
7.89–7.85 (m, 1H), 7.69–7.52 (m, 4H), 4.49–4.46 (m, 2H), 4.34–4.19 (m,
5H), 3.99–3.97 (m, 2H), 1.38 ppm (t, J=7.2 Hz, 6H); 13C NMR (75 MHz,
CDCl3): d=160.0 (d, J
127.6 (d, J(P,C)=6.1 Hz), 127.5 (d, J
(P,C)=13.7 Hz), 123.5, 116.7 (d, J(P,C)=189.6 Hz), 78.9, 62.7 (d, J
5.7 Hz), 61.9, 16.4 ppm (d, JACTHUNGTRNENGU
(P,C)=6.4 Hz); 31P NMR (121.4 MHz,
N
ACHTUNGTREN(NUNG P,C)=1.6 Hz), 128.4,
Naphthalene 5e: Eluent for column chromatography: hexanes/Et2O (3:2
v/v); yield: 57%; colorless oil; H NMR (300 MHz, CDCl3): d=8.23–8.21
1
G
ACHTUNGTRENNUNG
E
G
ACHTUNGTRENNUNG
(m, 1H), 7.87–7.84 (m, 1H), 7.67 (d, J=8.4 Hz, 1H), 7.55–7.44 (m, 5H),
7.36 (t, J=7.5 Hz, 1H), 7.19 (d, J=7.5 Hz, 1H), 3.84 (t, J=4.4 Hz, 2H),
3.63 (t, J=4.4 Hz, 2H), 2.42 (s, 3H), 1.56 ppm (s, 1H); 13C NMR
(75 MHz, CDCl3): d=151.4, 138.6, 138.3, 134.4, 130.6, 130.3, 128.5, 128.3,
128.0, 126.7, 126.4, 126.3, 124.3, 122.4, 75.5, 62.2, 21.6 ppm; IR (neat): n˜ =
3416 cmꢀ1; HRMS (ESI): m/z calcd for C19H19O2: 279.1380 [M+H]+;
found: 279.1385.
Dibenzocyclooctene 6l: Yield: 10%; colorless oil; 1H NMR (400 MHz,
CDCl3): d=7.98 (dd, J=7.6, 1.2 Hz, 1H), 7.64 (dd, J=8.0, 1.6 Hz, 1H),
7.31–7.17 (m, 5H), 7.08 (d, J=7.2 Hz, 1H), 5.75 (dd, J=9.2, 6.8 Hz, 1H),
4.23–4.21 (m, 1H), 3.88–3.77 (m, 3H), 2.90 (dd, J=14, 6.8 Hz, 1H), 2.72
(dd, J=14.0, 9.2 Hz, 1H), 1.24 ppm (s, 9H); 13C NMR (100 MHz,
CDCl3): d=152.2, 141.0, 140.4, 140.1, 139.8, 131.6, 128.7, 127.3, 127.2,
127.1, 127.0, 126.5, 126.4, 122.0, 109.6, 64.8, 64.6, 36.4, 35.2, 32.0 ppm; IR
(neat): n˜ =1479, 1268, 1186, 1077 cmꢀ1; HRMS (ESI): m/z calcd for
C20H19: 259.1481 [M+HꢀC2H6O2]+; found: 259.1484.
Spiro naphthalene 4m: Eluent for column chromatography: EtOAc;
yield: 79%; colorless prisms; m.p. 236–2388C (Et2O); 1H NMR
(400 MHz, CD2Cl2): d=7.93–7.94 (m, 2H), 7.66–7.61 (m, 2H), 7.48–7.43
(m, 2H), 7.30–7.12 (m, 11H), 7.06 (td, J=7.2, 1.2 Hz, 1H), 6.74–6.68 (m,
2H), 6.54 (dd, J=9.6, 6.4 Hz, 1H), 3.88–3.82 (m, 1H), 3.77–3.72 (m, 2H),
3.43–3.37 ppm (m, 1H); 31P NMR (161.9 MHz, CDCl3): d=32.16 ppm;
IR (Nujol): n˜ =1437, 1235, 1181, 1148, 1103 cmꢀ1; HRMS (ESI): m/z
calcd for C30H26O3P: 465.1614 [M+H]+; found: 465.1619.
Naphthalene 5 f: Eluent for column chromatography: hexanes/Et2O (4:1
v/v); yield: 58%; colorless prisms; m.p. 113–1158C (pentane); 1H NMR
(300 MHz, CDCl3): d=8.23 (dd, J=7.5, 1.5 Hz, 1H), 7.87 (dd, J=7.5,
1.5 Hz, 1H), 7.69 (d, J=8.4 Hz, 1H), 7.59–7.55 (m, 3H), 7.53–7.48 (m,
2H), 7.31 (d, J=8.1 Hz, 2H), 3.87 (t, J=4.5 Hz, 2H), 3.66 (t, J=4.5 Hz,
2H), 2.43 (s, 3H), 1.64 ppm (s, 1H); 13C NMR (75 MHz, CDCl3): d=
151.2, 137.2, 135.5, 134.2, 130.2, 129.3, 129.2, 128.4, 128.0, 126.2, 126.1,
124.2, 122.2, 75.2, 62.0, 21.2 ppm; IR (Nujol): n˜ =3541 cmꢀ1; HRMS
(ESI): m/z calcd for C19H19O2: 279.1380 [M+H]+; found: 279.1386.
Naphthalene 5g: Eluent for column chromatography: hexanes/Et2O (4:1
v/v); yield: 65%; colorless prisms; m.p. 133–1358C (pentane); 1H NMR
(300 MHz, CDCl3): d=8.23 (d, J=7.2 Hz, 1H), 7.87 (d, J=7.2 Hz, 1H),
7.68 (d, J=8.7 Hz, 1H), 7.62 (d, J=8.7 Hz, 2H), 7.57–7.46 (m, 3H), 7.02
(d, J=8.7 Hz, 2H), 3.87–3.84 (m, 5H), 3.66 (t, J=4.5 Hz, 2H), 1.62 ppm
(s, 1H); 13C NMR (75 MHz, CDCl3): d=159.0, 151.2, 134.2, 130.8, 130.7,
130.0, 128.5, 128.0, 126.4, 126.2, 124.3, 122.3, 114.0, 75.2, 62.2, 55.4 ppm;
Spiro naphthalene 4n: Eluent for column chromatography: hexanes/
EtOAc (7:3 v/v); yield: 65%; colorless oil; 1H NMR (300 MHz, CD2Cl2):
d=7.90–7.87 (m, 2H), 7.31–7.15 (m, 7H), 6.80 (dd, J=9.9, 3.9 Hz, 1H),
6.24 (dd, J=9.9, 6.9 Hz, 1H), 4.01–3.56 (m, 7H), 3.37 (q, J=7.5 Hz, 1H),
0.97 ppm (td, J=6.9, 3.6 Hz, 6H); 13C NMR (75 MHz, CD2Cl2): d=136.5
IR (Nujol): n˜ =3417 cmꢀ1
; HRMS (ESI): m/z calcd for C19H19O3:
295.1329 [M+H]+; found: 295.1335.
Naphthalene 5h: Eluent for column chromatography: EtOAc; yield:
80%; colorless prisms; m.p. 215–2178C (Et2O); 1H NMR (300 MHz,
CDCl3): d=8.10 (d, J=8.1 Hz, 1H), 7.87 (d, J=7.5 Hz, 1H), 7.72–7.62
(m, 4H), 7.60–7.44 (m, 9H), 6.91 (dd, J=12.0, 8.4 Hz, 1H), 4.49 (t, J=
3.9 Hz, 2H), 4.40 (s, 1H), 3.85 ppm (t, J=3.9 Hz, 2H); 13C NMR
(d, J
131.1 (d, J
128.0, 127.1, 124.0, 110.0 (d, J
6.7 Hz), 62.7 (d, J(P,C)=6.9 Hz), 57.4 (d, J
(P,C)=4.1 Hz), 16.4 ppm (d, JAHCTUNGERNNUG
(P,C)=3.8 Hz); 31P NMR (121.4 MHz,
N
E
ACHTUNGTREN(NUNG P,C)=3.0 Hz),
E
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
R
ACHTUNGTRENNUNG
G
(75 MHz, CDCl3): d=161.7, 137.6, 133.1, 131.9 (d, J
(d, J(P,C)=9.8 Hz), 128.7 (d, J(P,C)=12.5 Hz), 128.5, 128.3 (d, J
(P,C)=7.4 Hz), 126.5, 123.6, 123.5 (d, JACTHUNGRTENNUGN
ACHTUNGTRENNUNG
z calcd for C22H26O5P: 401.1512 [M+H]+; found: 401.1518.
A
R
ACHTUNGTRENNUNG
11.0 Hz), 127.5 (d,
10.3 Hz), 119.9 (d,
(121.4 MHz, CDCl3): d=31.01 ppm; IR (Nujol): n˜ =3324 cmꢀ1; HRMS
(ESI): m/z calcd for C24H22O3P: 389.1301 [M+H]+; found: 389.1312.
J
G
Naphthalene [D]5h: Eluent for column chromatography: EtOAc; yield:
JACTHNUTRGNEUNG
(P,C)=104.8 Hz), 79.6, 62.1 ppm; 31P NMR
1
60%; white prisms; m.p. 213–2158C (Et2O); H NMR (300 MHz, CDCl3):
d=8.10 (d, J=8.1 Hz, 1H), 7.87 (d, J=7.5 Hz, 1H), 7.72–7.62 (m, 4H),
7.60–7.44 (m, 9H), 5.64 (br s, 1H), 4.49 (t, J=3.9 Hz, 2H), 3.85 ppm
Chem. Eur. J. 2013, 19, 16093 – 16103
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
16101

M. Alajarin, P. Sanchez-Andrada, A. Vidal et al.
(br s, 2H); 13C NMR (75 MHz, CDCl3): d=161.6, 137.6, 133.1, 131.9 (d,
(P,C)=2.5 Hz), 131.7 (d, J(P,C)=9.8 Hz), 128.7 (d, J(P,C)=12.5 Hz),
128.5, 127.5 (d, J(P,C)=7.4 Hz), 126.5, 123.6, 123.5 (d, J(P,C)=10.3 Hz),
119.9 (d,
1H), 7.81 (dd, J=8.4, 0.4 Hz, 1H), 7.72 (dd, J=8.4, 0.4 Hz, 1H), 7.52–
7.48 (m, 1H), 7.38–7.34 (m, 1H), 7.20 (s, 1H), 4.42 (q, J=7.2 Hz, 2H),
3.98 (s, 3H), 1.43 ppm (t, J=7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3):
d=166.2, 155.8, 136.0, 132.5, 128.6, 128.3, 127.5, 126.4, 124.3, 122.2, 106.8,
61.1, 56.0, 14.3 ppm; IR (neat): n˜ =1727 cmꢀ1; HRMS (ESI): m/z calcd
for C14H15O3: 231.1016 [M+H]+; found: 231.1022.
J
G
G
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
CDCl3) d=30.51 ppm; IR (Nujol): n˜ =3227 cmꢀ1; HRMS (ESI) m/z calcd
for C24H21DO3P: 390.1379 [M+H]+; found: 390.1382.
Naphthalene 21b: Eluent for column chromatography: hexanes/Et2O
(4:1 v/v); yield: 58%; yellow oil; 1H NMR (400 MHz, CDCl3): d=8.29–
8.25 (m, 1H), 7.85–7.79 (m, 2H), 7.61–7.53 (m, 3H), 4.06 (s, 3H),
1.67 ppm (s, 9H); 13C NMR (100 MHz, CDCl3): d=165.8, 157.5, 136.5,
128.6, 128.0, 127.8, 126.9, 126.4, 123.6, 123.5, 121.3, 81.5, 63.3, 28.3 ppm;
Preparation of naphthalenes 10 and 15: Et3N (0.07 mL, 0.5 mmol) was
added to a solution of sulfone 8 or 3-alkynoate 13 (5 mmol) in anhydrous
toluene (15 mL). The reaction mixture was heated at reflux for 4–5 h.
After cooling to RT, the solvent was removed under reduced pressure
and the resulting material was purified by column chromatography on
silica gel.
IR (neat): n˜ =1718 cmꢀ1
; HRMS (ESI): m/z calcd for C16H18NaO3:
281.1146 [M+Na]+; found: 281.1146.
Naphthalene 24b: Yield: 13%.
Naphthalene 10: Eluent for column chromatography: hexanes/EtOAc
(95:5 v/v); yield: 98%; colorless oil; 1H NMR (300 MHz, CDCl3): d=
8.32–8.29 (m, 2H), 8.24–8.20 (m, 2H), 8.16 (d, J=8.4 Hz, 1H), 8.11 (d,
J=9.0 Hz, 1H), 7.91 (d, J=7.8 Hz, 1H), 7.79 (d, J=9 Hz, 1H), 7.65 (td,
J=6.9, 0.9 Hz, 1H), 7.57 (td, J=6.9, 0.9 Hz, 1H), 4.52 (t, J=4.2 Hz, 2H),
4.13 (t, J=4.2 Hz, 2H), 2.41 ppm (s, 1H); 13C NMR (75 MHz, CDCl3):
d=155.7, 150.4, 147.6, 138.2, 129.8, 129.2, 128.7, 128.4, 127.8, 127.5, 125.3,
124.2, 123.9, 123.6, 79.2, 62.2 ppm; IR (neat): n˜ =3387 cmꢀ1; HRMS
(ESI): m/z calcd for C18H16NO6S: 374.0693 [M+H]+; found: 374.0688.
Preparation 1,2-dihydronaphthalene 28: A solution of allene 27 (1 mmol)
in anhydrous toluene (15 mL) was heated in a sealed tube at 1508C for
50 h. After cooling to RT, the solvent was removed under reduced pres-
sure and the resulting material was purified by column chromatography
on silica gel (hexanes/Et2O, 9:1 v/v).
1,2-Dihydronaphthalene 28: Yield: 40%; colorless oil; 1H NMR
(300 MHz, CD2Cl2): d=7.32–7.21 (m, 1H), 7.18–7.14 (m, 3H), 6.61 (dd,
J=9.9, 3.3 Hz, 1H), 6.11–6.07 (m, 1H), 4.16 (dd, J=3.9, 1.2 Hz, 1H),
3.12 (s, 3H), 2.25–2.22 (m, 1H), 1.14 ppm (s, 9H); 13C NMR (100 MHz,
CD2Cl2): d=133.8, 132.9, 129.8, 128.6, 126.9, 126.7, 126.1, 78.9, 55.4, 49.7,
32.4, 28.8 ppm; IR (neat): n˜ =1105, 1074 cmꢀ1; HRMS (ESI): m/z calcd
for C15H21O: 216.1515 [M+H]+; found: 216.1588.
Naphthalene 15a: Eluent for column chromatography: hexanes/Et2O (1:1
v/v); yield: 90%; colorless oil; 1H NMR (300 MHz, CDCl3): d=8.27 (d,
J=7.5 Hz, 1H), 7.90 (d, J=11.6 Hz, 1H), 7.84 (d, J=7.5 Hz, 1H), 7.63–
7.54 (m, 3H), 4.42 (q, J=6.9 Hz, 2H), 4.32 (t, J=4.2 Hz, 2H), 4.02 (t, J=
4.2 Hz, 2H), 3.49 (s, 1H), 1.42 ppm (t, J=6.9 Hz, 3H); 13C NMR
(75 MHz, CDCl3): d=166.2, 157.4, 136.9, 128.5, 128.1, 126.7, 126.6, 123.9,
123.7, 119.3, 77.9, 62.0, 61.4, 14.3 ppm; IR (neat): n˜ =3466 cmꢀ1; HRMS
(ESI): m/z calcd for C15H17O4: 261.1121 [M+H]+; found: 261.1126.
Preparation of compounds 29 and 30: Sodium hydride (60% in oil,
0.25 g, 6.25 mmol) was added to a solution of naphthalene 5k (0.32 g,
1 mmol) or 15a (0.26 g, 1 mmol) in anhydrous THF (15 mL). The reac-
tion mixture was stirred at RT under a nitrogen atmosphere for 5 h.
Then, the THF was removed under reduced pressure and the resulting
material was partitioned between Et2O (30 mL) and water (30 mL). The
organic layer was separated and dried over anhydrous MgSO4. After
evaporation of the solvent, the residue was purified by column chroma-
tography on silica gel (EtOAc).
Naphthalene 15b: Eluent for column chromatography: hexanes/Et2O
(3:2 v/v); yield: 90%; colorless oil; 1H NMR (300 MHz, CDCl3): d=
8.27–8.24 (m, 1H), 7.86–7.80 (m, 2H), 7.61–7.54 (m, 3H), 4.32 (t, J=
4.2 Hz, 2H), 4.03–3.91 (m, 2H), 3.89–3.85 (m, 1H), 1.64 ppm (s, 9H);
13C NMR (75 MHz, CDCl3): d=165.7, 156.9, 136.7, 128.5, 128.2, 128.0,
126.8, 126.5, 123.7, 123.6, 120.9, 82.1, 77.8, 62.0, 28.3 ppm; IR (neat): n˜ =
3473 cmꢀ1; HRMS (ESI): m/z calcd for C17H20NaO4: 311.1254 [M+H]+;
found: 311.1255.
Compound 29: Yield: 94%; colorless prisms; m.p. 91–898C (Et2O);
1H NMR (300 MHz, CDCl3): d=8.29 (d, J=7.8 Hz, 1H), 7.86–7.76 (m,
2H), 7.66–7.52 (m, 3H), 4.68–4.36 (m, 4H), 4.22–4.02 (m, 2H), 1.32 ppm
Naphthalene 15c: Eluent for column chromatography: hexanes/Et2O (3:2
(t, J=7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): d=158.5 (d, J
ACHTUNGTRENNUNG
1
v/v); yield: 57%; colorless oil; H NMR (300 MHz, CDCl3): d=8.25–8.22
3.8 Hz), 136.7 (d, JACTHUNGTREN(NUGN P,C)=1.8 Hz), 128.7, 127.8, 127.7, 127.0 (d, JACHTUNGTRENNUNG
(m, 1H), 7.90–7.81 (m, 2H), 7.61–7.51 (m, 3H), 4.42 (q, J=7.2 Hz, 2H),
4.25 (t, J=5.7 Hz, 2H), 4.07 (br s, 2H), 3.47 (s, 1H), 2.20–2.11 (m, 2H),
1.41 ppm (t, J=7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): d=166.0,
157.4, 136.8, 128.6, 128.4, 127.9, 126.6, 123.7, 123.5, 119.3, 73.2, 61.2, 59.7,
32.8, 14.3 ppm; IR (neat): n˜ =3458 cmꢀ1; HRMS (ESI): m/z calcd for
C16H19O4: 275.1278 [M+H]+; found: 275.1282.
12.2 Hz), 126.7, 123.5 (d,
177.1 Hz), 72.8, 67.9 (d,
J
J
U
JACHTUNGTRENNUNG
N
JACHTUNGTRENNUNG
16.3 ppm (d, JACTHNUTRGENUG(N P,C)=6.4 Hz); IR (neat): n˜ =1354, 1327, 1297, 1271, 1258,
1020 cmꢀ1; HRMS (ESI): m/z calcd for C14H16O4P: 279.0781 [M+H]+;
found: 279.0788.
Compound 30: Yield: 67%.
Naphthalene 15d: Eluent for column chromatography: hexanes/Et2O
(3:2 v/v); yield: 77%; yellow oil; 1H NMR (300 MHz, CDCl3): d=8.25–
8.20 (m, 1H), 7.85–7.77 (m, 2H), 7.60–7.52 (m, 3H), 4.26 (t, J=5.7 Hz,
2H), 4.04–4.02 (m, 2H), 3.51 (s, 1H), 2.18–2.10 (m, 2H), 1.64 ppm (s,
9H); 13C NMR (75 MHz, CDCl3): d=165.6, 156.8, 136.6, 128.7, 128.2,
127.9, 126.7, 126.5, 123.6, 123.5, 121.1, 81.9, 72.9, 59.6, 32.9, 28.3 ppm; IR
(neat): n˜ =3434 cmꢀ1; HRMS (ESI): m/z calcd for C18H22NaO4: 325.1410
[M+Na]+; found: 325.1411.
Acknowledgements
This work was supported by the Ministerio de Ciencia e Innovacion of
Spain (Project No. CTQ2008-05827/BQU) and the Fundacion Seneca-
CARM (Project No. 08661/PI/08). B.B. thanks the Fundacion Seneca-
CARM for a fellowship.
Preparation of naphthalenes 21 and 24: Et3N (0.07 mL, 0.5 mmol) was
added to a solution of 3-alkynoate 17 (5 mmol) in anhydrous toluene
(15 mL). The reaction mixture was heated at reflux for 4 h. After cooling
to RT, the solvent was removed under reduced pressure and the resulting
material was purified by column chromatography on silica gel.
[1] For reviews on the chemistry of allenes, see: a) Modern Allene
Chemistry (Eds: N. Krause, A. S. K. Hashmi), Wiley-VCH, Wein-
heim, 2004; b) S. Ma, Chem. Rev. 2005, 105, 2829–2872; c) R.
Zimmer, C. U. Dinesh, E. Nandanan, F. A. Khan, Chem. Rev. 2000,
100, 3067–3126; d) J. Marshall, Chem. Rev. 2000, 100, 3163–3186;
e) A. S. K. Hashmi, Angew. Chem. 2000, 112, 3737–3740; Angew.
Chem. Int. Ed. 2000, 39, 2285; f) R. W. Bates, V. Satcharoen, Chem.
Soc. Rev. 2002, 31, 12–21; g) L. K. Sydnes, Chem. Rev. 2003, 103,
1133–1150; h) S. Ma, Acc. Chem. Res. 2003, 36, 701–712; i) L.
Brandsma, N. A. Nedolya, Synthesis 2004, 735–745; j) L.-L. Wei, H.
Xiong, R. P. Hsung, Acc. Chem. Res. 2003, 36, 773–782; k) X. Lu, C.
Naphthalene 21a: Eluent for column chromatography: hexanes/Et2O
(4:1 v/v); yield: 72%; yellow oil; 1H NMR (300 MHz, CDCl3): d=8.30–
8.25 (m, 1H), 7.89–7.83 (m, 2H), 7.63–7.53 (m, 3H), 4.45 (q, J=7.2 Hz,
2H), 4.07 (s, 3H), 1.45 ppm (t, J=7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): d=166.4, 158.1, 136.7, 128.6, 128.3, 127.9, 126.7, 126.5, 123.6,
119.6, 63.4, 61.2, 14.4 ppm; IR (neat): n˜ =1723 cmꢀ1; HRMS (ESI): m/z
calcd for C14H15O3: 231.1010 [M+H]+; found: 231.1020.
Naphthalene 24a: Eluent for column chromatography: hexanes/Et2O
1
(4:1 v/v); yield: 20%; yellow oil; H NMR (400 MHz, CDCl3): d=8.28 (s,
16102
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ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 16093 – 16103

Cyclization of ortho-1,3-Dioxolan-2-yl-Substituted Phenylallenes
FULL PAPER
Zhang, Z. Xu, Acc. Chem. Res. 2001, 34, 535–544; l) K. K. Wang,
Chem. Rev. 1996, 96, 207–222; m) H. H. A. M. Hassan, Curr. Org.
Synth. 2007, 4, 413–439; n) S. Ma, Aldrichimica Acta 2007, 40, 91–
102; o) T. Pinho e Melo, Curr. Org. Chem. 2009, 13, 1406–1431; p) F.
Lꢃpez, J.-L. Mascarenas, Chem. Eur. J. 2011, 17, 418–428; q) T. Pin-
ho e Melo, Monatsh. Chem. 2011, 142, 681–697; r) S. Yu, S. Ma,
Angew. Chem. 2012, 124, 3128–3167; Angew. Chem. Int. Ed. 2012,
51, 3074–3112; s) T. Lu, Z. Lu, Z.-X. Ma, Y. Zhang, R. P. Hsung,
Chem. Rev. 2013, 113, 4862–4904.
1995, 117, 7487–7492; e) E. M. VanAlstyne, A. W. Norman, W. H.
Okamura, J. Am. Chem. Soc. 1994, 116, 6207–6216; f) G. Y. Shen,
R. Tapia, W. H. Okamura, J. Am. Chem. Soc. 1987, 109, 7499–7506;
g) S. H. Barrack, W. H. Okamura, J. Org. Chem. 1986, 51, 3201–
3206; h) G. A. Leyes, W. H. Okamura, J. Am. Chem. Soc. 1982, 104,
6099–6105.
[7] a) H. Heimgartner, J. Zsindely, H. J. Hansen, H. Schmid, Helv.
Chim. Acta 1970, 53, 1212–1215; b) H. Heimgartner, J. Zsindely, H.-
J. Hansen, H. Schmid, Helv. Chim. Acta 1973, 56, 2924–2945.
[8] W. Grimme, T. Grommes, W. R. Roth, R. Breuckmann, Angew.
Chem. 1992, 104, 867–869; Angew. Chem. Int. Ed. Engl. 1992, 31,
872–874.
[2] For examples of [m+n] cycloaddition reactions that involve allenes,
see: a) W. R. Doblier, Jr., S. L. Weaver, J. Org. Chem. 1990, 55,
711–715; b) H.-Y. Lee, J.-H. Sohn, H. Y. Kim, Tetrahedron Lett.
2001, 42, 1695–1698; c) M. Kimura, Y. Horino, Y. Wakamiya, T.
Okajima, Y. Tamaru, J. Am. Chem. Soc. 1997, 119, 10869–10870;
d) M. Bertrand, G. Gil, A. Junino, R. Maurin, Tetrahedron 1985, 41,
2759–2764; e) M. Bertrand, J. L. Gras, J. Gore, Tetrahedron 1975,
31, 857–862; f) S. Kitagaki, Y. Okumura, C. Mukai, Tetrahedron
Lett. 2006, 47, 1849–1852; g) S. Kitagaki, Y. Okumura, C. Mukai,
Tetrahedron 2006, 62, 10311–10320; h) S. Braverman, E. V. K. Sure-
sh Kumar, M. Cherkinsky, M. Sprecher, I. Goldberg, Tetrahedron
2005, 61, 3547–3557; i) J. D. Winkler, J. R. Ragains, Org. Lett. 2006,
8, 4031–4033; j) H. Ohno, T. Mizutani, Y. Kadoh, K. Miyamura, T.
Tanaka, Angew. Chem. 2005, 117, 5243–5245; Angew. Chem. Int.
Ed. 2005, 44, 5113–5115; k) K. M. Brummond, D. Chen, Org. Lett.
2005, 7, 3473–3475; l) M. E. Jung, N. Nishimura, A. R. Novack, J.
Am. Chem. Soc. 2005, 127, 11206–11207; m) M. E. Jung, A. R.
Novack, Tetrahedron Lett. 2005, 46, 8237–8240; n) S. Aoyagi, M.
Hakoshi, M. Suzuki, Y. Nakanoya, K. Shimada, Y. Takikawa, Tetra-
hedron Lett. 2006, 47, 7763–7766; o) T. Yoshino, F. Ng, S. J. Dani-
shefsky, J. Am. Chem. Soc. 2006, 128, 14185–14191; p) Y. S. Tran, O.
Kwon, Org. Lett. 2005, 7, 4289–4291; q) M. E. Jung, S.-J. Min, J.
Am. Chem. Soc. 2005, 127, 10834–10835; r) D. Regꢁs, J. M. Ruiz,
M. M. Alfonso, J. A. Palenzuela, J. Org. Chem. 2006, 71, 9153–9164;
s) J. A. Souto, C. S. Lꢃpez, O. N. Faza, R. Alvarez, A. R. de Lera,
Org. Lett. 2005, 7, 1565–1568; t) S. Kitagaki, K. Ohdachi, K. Katoh,
C. Mukai, Org. Lett. 2006, 8, 95–98; u) K. S. Feldman, M. R. Iyer, J.
Am. Chem. Soc. 2005, 127, 4590–4591; v) X. Lu, X. Zhang, Tetrahe-
dron 2006, 62, 457–460; w) A. Scherer, J. A. Gladysz, Tetrahedron
Lett. 2006, 47, 6335–6337; x) J. R. Bull, N. S. Desmond-Smith, S. J.
Heggie, R. Hunter, F. C. Tien, Synlett 1998, 900–902; y) M. Aso, I.
Ikeda, T. Kawave, M. Shiro, K. Kanematsu, Tetrahedron Lett. 1992,
33, 5787–5790; z) I. Ikeda, K. Honda, E. Osawa, M. Shiro, M. Aso,
K. Kanematsu, J. Org. Chem. 1996, 61, 2031–2037.
[9] Z. Gu, S. Ma, Chem. Eur. J. 2008, 14, 2453–2464.
[10] a) M. Alajarꢀn, B. Bonillo, M.-M. Ortin, P. Sanchez-Andrada, A.
Vidal, Org. Lett. 2006, 8, 5645–5648; b) M. Alajarin, B. Bonillo, M.-
M. Ortin, P. Sanchez-Andrada, A. Vidal, Eur. J. Org. Chem. 2011,
1896–1913; c) M. Alajarin, B. Bonillo, P. Sanchez-Andrada, A.
Vidal, D. Bautista, Org. Lett. 2009, 11, 1365–1368; d) M. Alajarꢀn,
B. Bonillo, P. Sanchez-Andrada, A. Vidal, J. Org. Chem. 2010, 75,
3737–3750; e) M. Alajarꢀn, B. Bonillo, M. Marin-Luna, P. Sanchez-
Andrada, A. Vidal, R.-A. Orenes, Tetrahedron 2012, 68, 4672–4681;
f) M. Alajarꢀn, B. Bonillo, R.-A. Orenes, M.-M. Ortin, A, Vidal,
Org. Biomol. Chem. 2012, 10, 9523–9537.
[11] J. B. Feltenberger, R. P. Hsung, Org. Lett. 2011, 13, 3114–3117.
[12] For examples of sequential [1,5]-H shift/8p-electrocyclization reac-
tions of allenes, see: a) S. Ma, Z. Gu, J. Am. Chem. Soc. 2006, 128,
4942–4943; b) C. Zhu, X. Zhang, X. Lian, S. Ma, Angew. Chem.
2012, 124, 7937–7940; Angew. Chem. Int. Ed. 2012, 51, 7817–7820.
[13] L.-Z. Dai, M. Shi, Chem. Eur. J. 2010, 16, 2496–2502.
[14] a) R. Shen, X. Huang, L. Chen, Adv. Synth. Catal. 2008, 350, 2865–
2870; b) J. Cao, X. Huang, Org. Lett. 2010, 12, 5048–5051; c) R.
Shen, L. Chen, X. Huang, Adv. Synth. Catal. 2009, 351, 2833–2838;
d) A. Padwa, H. Lipka, S. H. Watterson, S. S. Murphree, J. Org.
Chem. 2003, 68, 6238–6250; e) A. Suꢁrez, G. C. Fu, Angew. Chem.
2004, 116, 3664–3666; Angew. Chem. Int. Ed. 2004, 43, 3580–3582.
[15] M. Alajarin, M. Marin-Luna, A. Vidal, Adv. Synth. Catal. 2011, 353,
557–562.
[16] The proposed assignment of a relative cis-disposition of the methoxy
and tert-butyl groups at the C1 and C2 carbon atoms of cis-2-(tert-
butyl)-1-methoxy-1,2-dihydronaphthalene (32) was based on a com-
parison of the chemical shifts of the protons of the tert-butyl groups
in compound 32 (C
cis-2-(tert-butyl)-1-hydroxy-1,2-dihydronaphthalene (C
1.18 ppm) and trans-2-(tert-butyl)-1-hydroxy-1,2-dihydronaphthalene
(C
(CH3)3, d=0.89 ppm). For the 1H NMR data of cis-2-(tert-butyl)-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
[3] For examples of Alder-ene reactions that involve allenes, see: a) K.
Nꢄrhi, J. Franzꢅn, J.-E. Bꢄckvall, J. Org. Chem. 2006, 71, 2914–2917;
b) A. S. K. Hashmi, G. Szeimies, Chem. Ber. 1994, 127, 1075–1089;
c) R. Shen, S. Zhu, X. Huang, J. Org. Chem. 2009, 74, 4118–4123;
d) K. M. Brummond, T. O. Painter, D. A. Probst, B. Mitasev, Org.
Lett. 2007, 9, 347–349; e) K. M. Brummond, J. M. McCabe, Tetrahe-
dron 2006, 62, 10541–10554; f) ref. [3a]; g) K. M. Brummond, B. Mi-
tasev, Org. Lett. 2004, 6, 2245–2248; h) K. M. Brummond, H. Chen,
P. Sill, L. You, J. Am. Chem. Soc. 2002, 124, 15186–15187.
AHCTUNGTRENNUNG
1-hydroxy-1,2-dihydronaphthalene, see: M. Lautens, J.-L. Renaud, S.
Hiebert, J. Am. Chem. Soc. 2000, 122, 1804–1805. For the 1H NMR
data of trans-2-(tert-butyl)-1-hydroxy-1,2-dihydronaphthalene, see:
W. Zhang, S.-F- Zhu, X.-C. Qiao, Q.-L. Zhou, Chem. Asian J. 2008,
3, 2105–2111.
[17] In fact, compounds 31 and 31c are identical to compounds 3a and
3c, respectively.
[4] For examples of [1,7]-H shifts in allenes, see: a) I. D. Gridnev, M. E.
Gurskii, A. V. Ignatenko, Y. N. Bubnov, Y. V. Ilꢀchev, Organometal-
lics 1993, 12, 2487–2495; b) W. H. Okamura, H. Y. Elnagar, M.
Ruther, S. Dobreff, J. Org. Chem. 1993, 58, 600–610; c) C. A.
Hoeger, W. H. Okamura, J. Am. Chem. Soc. 1985, 107, 268–270;
d) H. Y. Elnagar, W. H. Okamura, J. Org. Chem. 1988, 53, 3060–
3066.
[18] a) R. B. Woodward, R. Hoffmann, Angew. Chem. 1969, 81, 797–
869; Angew. Chem. Int. Ed. Engl. 1969, 8, 781–853; b) R. B. Wood-
ward, R. Hoffmann, The Conservation of Orbital Symmetry, Wiley-
VCH, Weinheim, 1970; c) K. N. Houk, Y. Li, J. D. Evanseck, Angew.
Chem. 1992, 104, 711–739; Angew. Chem. Int. Ed. Engl. 1992, 31,
682–708.
[19] K. Sato, K. Uenishi, Jpn. Kokai Tokkyo Koho 2002, JP 2002251011
A 20020906.
[20] M. Lamothe, P. L. Fuchs, J. Am. Chem. Soc. 1993, 115, 4483–4496.
[5] K.-M. Wu, M. M. Middland, W. H. Okamura, J. Org. Chem. 1990,
55, 4381–4392.
[6] For examples of [1,5]-H shifts in allenes, see: a) J. A. Palenzuela,
H. Y. Elnagar, W. H. Okamura, J. Am. Chem. Soc. 1989, 111, 1770–
1773; b) D. E. Minter, G. J. Fonken, F. T. Cook, Tetrahedron Lett.
1979, 20, 711–714; c) S. K. Verma, E. B. Fleischer, H. W. Moore, J.
Org. Chem. 2000, 65, 8564–8573; d) F. Jensen, J. Am. Chem. Soc.
Received: April 26, 2013
Revised: August 23, 2013
Published online: October 7, 2013
Chem. Eur. J. 2013, 19, 16093 – 16103
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
16103