Palladium catalysed reaction of allene with phenols. Phenoxymethyl-1,3-dienes and their further reactions

Article abstract of DOI:10.1016/S0040-4020(01)00771-2

A 3-step 100% atom economic sequence is reported whereby a variety of phenols react with 2 mol equiv. of allene to give phenoxymethyl-1,3-dienyl ethers. Subsequent thermal Claisen rearrangement to C-1,3-dienes and acid catalysed ring closure furnishes 3:1

Full text of DOI:10.1016/S0040-4020(01)00771-2

TETRAHEDRON
Pergamon
Tetrahedron 57 ;2001) 7965±7978
Palladium catalysed reaction of allene with phenols.
Phenoxymethyl-1,3-dienes and their further reactions
Ronald Grigg,a,p Ngampong Kongkathip,b Boonsong Kongkathip,b Suwaporn Luangkamina
and H. Ali Dondasc
aMolecular Innovation, Diversity and Automated Synthesis ꢀMIDAS) Centre, School of Chemistry, Leeds University, Leeds LS2 9JT, UK
bChemistry Department, Faculty of Science, Kasetsart University, Bangkok, Thailand
cChemistry Department, Science and Arts Faculty, Mersin University, Mersin, Turkey
Received 11 May 2001; revised 25 June 2001; accepted 19 July 2001
AbstractÐA 3-step 100% atom economic sequence is reported whereby a variety of phenols react with 2 mol equiv. of allene to give
phenoxymethyl-1,3-dienyl ethers. Subsequent thermal Claisen rearrangement to C-1,3-dienes and acid catalysed ring closure furnishes
3:1±6.5:1 mixtures of exo-methylene chromans and dihydrobenzofurans with the former predominating. q 2001 Elsevier Science Ltd.
All rights reserved.
Palladium catalysed reactions of allenes are proving a
remarkably fertile source of new reactions.1,2 In the majority
of cases disclosed to date the reactions involve an aryl/vinyl
halide or allylic ester as co-substrate and a Pd;0) catalyst.
However there are numerous examples of Pd;II) catalysed
nucleophilic attack on allenes.3 A further less well explored
class of reactions involves Pd;0) and substrates with X±H
bonds ;where Xˆheteroatom). Thus allene reacts with
appropriate NH and OH compounds and carbon monoxide
in the presence of a Pd;0) catalyst to give methacrylamides
and methacrylate esters.4 The attraction of this type of
process is that it is 100% atom economic. An early pioneer-
ing paper by Coulson5 reported the reaction of allene with
primary and secondary amines to give aminomethyl-1,3-
dienes ;Scheme 1).6 This earlier report and our continuing
interest in the palladium catalysed reactions of allenes
encouraged us to explore the Pd;0) catalysed reactions of
phenols with allene. Such processes are 100% atom
economic and can conceptually be combined with other
100% atom economic processes. Two such processes,
Claisen rearrangement of O-dienyl to C-dienyl phenols
and subsequent acid catalysed cyclisation of the C-dienyl
phenols to annulated dihydrofurans and chromans were
deemed worthy of further study. Together they provide a
three-step sequence to interesting heterocycles, which are
present in many natural products, and require no protecting
group strategies. We now report the results of these studies.
1. Phenoxymethyl-1,3-dienes
A range of aryl and heteroaryl phenols were found to react
;Scheme 2) with allene ;1 bar) in THF over 16 h with an in
situ generated Pd;0) catalyst ;Table 1) in a Schlenk tube.
5 mol% Palladium acetate and 10 mol% tris-;2-furyl)
phosphine proved an effective catalyst system while
Pd;PPh3)4 was less effective. The yields of the derived
dienyl ethers 1±12 ;Scheme 2) varied depending on the
substrate structure.
Low yields of dienyl ethers were encountered in the case of
1,3,5-trihydroxybenzene ;entry 6), 3-hydroxypyridine
;entry 7) and 2-hydroxyisoquinoline ;entries 11 and 12).
The marked increase in yield when 3,5-dimethoxyphenol
was the substrate ;entry 5) suggests prototropic processes
;keto-enol type) may be responsible for the low yield in the
case of the trihydroxybenzene ;possibly leading to C-dienyl
byproducts). In the case of 3-hydroxypyridine the zwitter-
ionic form 13 may interfere with dienyl ether formation
while 3-hydroxyisoquinoline is known to equilibrate with
Scheme 1.
Keywords: chromans; dihydrobenzofurans; atom economy; Claisen
rearrangement; cyclisation.
Corresponding author. E-mail: r.grigg@chem.leeds.ac.uk
p
Scheme 2.
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020;01)00771-2

7966
Table 1. Dienyl ether synthesis from aryl/heteroaryl phenols and allene
Entry Phenol
R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
Product
Yield ;%)a

R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
7967
Table 1. ;continued)
Entry
Phenol
Product
Yield ;%)a
All reactions were carried out in THF in a Schlenk tube for 16 h at 808C with 1 bar of allene.
Isolated yields.
a
b
Allene ;1.5 bar) was used.
Reaction temperature 608C.
Reaction temperature 1008C.
c
d
its tautomer 14. The position of this latter equilibrium is
sensitive to solvent polarity7 and may be responsible for
the low yield.
A third type of product, a C-dienyl species, is obtained from
both 2-naphthol and 6-hydroxyquinoline which give 16
;50%) and 17 ;60%), respectively, using 5 mol%
Pd;PPh3)4 as catalyst ;Scheme 3).
In pursuing the O-versus C-diene formation we explored the
reaction ;THF, 808C) of 9-phenanthrol with allene ;1 bar)
using 5 mol% Pd;PPh3)4 as catalyst. In this case C-dienyl-
ation occurred twice, affording 18 in 53% yield ;Scheme 4).
The reaction of 3-hydroxyisoquinoline under more forcing
conditions leads to a 1:1.6 mixture of 11 and the 2-propenyl
ether 12. Formation of an analogous 2-propenyl ether 15
;42%) is observed when 4-nitrophenol is reacted ;THF,
1108C, 19 h) with allene ;1 bar) in the presence of 5 mol%
Pd;PPh3)4. This formal addition of NuH to allene was
discussed in a previous paper.4
Scheme 3.

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R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
rearrangements of allylic thionolesters13 and allylic
imidates14 have been reported and it appears that different
mechanisms operate for the Pd;0) and Pd;II) catalysed
processes. In our cases the products can be accounted for
by Scheme 5.
The formation of the O-dienylether is fast but reversible
whilst formation of the C-dienyl phenol is slow and essen-
tially irreversible under the reaction conditions. The
presence of a higher concentration of oxaphilic phosphine
when Pd;PPh3)4 is used as catalyst may assist in shielding
the negatively-charged phenolate oxygen and hence
promote C-alkylation. In the case of 9-phenanthrol the
high degree of ole®nic character15 of the `9,10-double
bond' suggest C-alkylation will be especially facile.
Scheme 4.
The C-dienyl species 16±18 could arise by direct C-alkyl-
ation of the ambident phenolate anions or they could be
generated by O-alkylation followed by a Claisen rearrange-
ment. There are comparatively few reports of the related
palladium catalysed alkylation of phenols with allyl
carbonates, acetates or related p-allylpalladium;II) pre-
cursors.8±10 In these latter studies the products are O-allyl
ethers apart from the products from phloroglucinol and
b-naphthol, which undergo C-allylation with allyl acetates.
Further study of the b-naphthol case showed the O-allyl
derivative was the kinetic product ;at 2208C) but rear-
ranged to the C-allyl derivative at higher temperatures.
Formation of C-alkylation products, which convert to non-
identi®ed products could therefore account for the low
yields in Table 1 ;entries 6, 7 and 11).
2. Mechanism of dienyl ether formation
Coulson showed the reaction of allene with N-deuteriomor-
pholine gave a morpholino-1,3-diene speci®cally labelled in
the methyl group ;95^3%) ;possibly with a trace amount of
deuterium in the adjacent methylene group).5 The simplest
way to account for this labelling pattern as applied to
generic nucleophiles, NuH, via the usual Pd;0)/Pd;II)
redox shuttle is shown in Scheme 6. In Scheme 6 only the
h1-complexes, and not the h3-complexes, are shown for
brevity.
In Scheme 6 intermediate 20 could conceptually revert to
the Pd±D species 19 or transform into the Pd±H species 21.
Assuming Scheme 6 is correct the distribution of deuterium
shows such reverse reactions to be negligible. An alternative
sequence involving a Pd;IV) intermediate is shown in
Scheme 7, which is based on Coulson's suggestion5 that 22
might be a key intermediate. Attack of Nu on the p-allyl
species could occur externally or by transfer from Pd;II)
depending on the nature of the nucleophile.
Evidence that formation of 16 proceeds via O-dienyl ether
10 was provided by two supplementary experiments. In the
®rst of these the reaction of b-naphthol with allene was
carried out in THF at 908C, as opposed to 608C in Table
1, for 16 h with the Pd;OAc)2±tris-;2-furyl)phosphine
catalyst system. The product ;68%) was the C-dienyl-
naphthalene 16 together with a trace amount of 10. When
O-dienylether 10 was reacted in THF at 608C for 32 h in the
presence of 5 mol% Pd;PPh3)4 it rearranged to 16 in 54%
yield. These results suggest 17 and 18 may also arise via
analogous O-alkylation±rearrangement sequences.
Pd;IV) intermediates have been demonstrated or suggested
for a range of reactions in recent years.6
Pd;II) and Hg;II) salts are known to catalyse both the Cope
and hetero-3,3-sigmatropic rearrangements via
a
3. Claisen rearrangement of O-dienylethers
cyclisation-induced rearrangement mechanism.11 These
processes are variants of the electrophile-induced additions
to alkenes where the metal cation is the electrophile. Pd;II)
catalysed rearrangement of allyl vinyl ethers has been
reported but there are strict structural requirements for this
process.12 Catalysis of the Claisen rearrangement of O-allyl-
phenolic ethers by Pd;II) salts has not been reported. In the
case of the rearrangement of 10!16 the catalytically active
species appears to be Pd;0). Pd;II) and Pd;0) catalysed
The Claisen rearrangement of dienyl ethers 1, 2, 5, 8 and 9
was studied in DMF at 2058C ;oil bath temperature) in a
Schlenk tube. The expected rearrangement ;Scheme 8)
occurred furnishing the C-dienes 22±27 in 20±63% yield
;Table 2).
The two low yielding reactions ;Table 2, entries 1 and 2)
were due to incomplete reaction with the mass balance
Scheme 5.

R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
7969
Scheme 6.
Scheme 7.
consisting largely of unreacted starting material. The more
facile rearrangement of the 1-naphthyl O-dienylether
compared to the 2-naphthyl O-dienylether ;Table 2, entries
5 and 6) is ascribed to steric acceleration due to the
buttressing effect of the C;8)-peri-H in the former case.16
4. Cyclisation of the 2-*1,3-dienylmethyl)-phenols
Cyclisation of the dienylmethyl phenols occurred at room
Scheme 8.

7970
Table 2. Claisen rearrangement of O-dienyl aryl ethers
Entry Ether
R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
Product
Reaction time ;h) Yielda ;%)
Reactions carried out in DMF in a Schlenk tube at 2058C.
Isolated yields.
a
Scheme 9.

R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
Table 3. Acid catalysed cyclisation products of 2-;1,3-dienylmethyl)-phenols
Entry Phenol
7971
Product
Yielda ;%)
All reactions carried out in CH2Cl2 in a Schlenk tube at room temperature using TsOH ;0.5 equiv.) and a trace of TFA.
Isolated yields.
a
temperature in methylene chloride in the presence of
p-toluenesulphonic acid ;0.5 equiv.) and a trace of TFA.
The products were a mixture of exo-methylene chromans
and dihydrobenzofurans ;Scheme 9) ;Table 3).
furan showed the ratio did not alter over 24±48 h. It did not
prove possible to separate these isomeric mixtures chroma-
tographically.
The observed product ratios could be interpreted in terms of
stereoelectronic effects. The two carbocations 39 and 40 are
both tertiary and allylic but in the case of 40 further
stabilisation, and lower reactivity, might result from aryl
p-participation 41 ;RˆH).
In most cases the major product is the exo-methylene
chroman except for the dienylmethyl phenol 24, which
gave a 1:1.5 mixture ;56%) of chroman and dihydrobenzo-
furan. Monitoring of the ratio of chroman to dihydrobenzo-

7972
R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
17, which shows the greatest preference for chroman forma-
tion ;Table 3, entry 2), has the lowest pKa ;8.9)17 of those
studied. The increased phenoxide ion stability is thus
re¯ected in the greater discrimination observed in this case.
5. Experimental
Melting points were determined on a Kof¯er hot-stage
apparatus and are uncorrected. Mass spectral data were
obtained on a VG Autospec instrument at 70 eV. Nuclear
magnetic resonance spectra were recorded at 250 MHz on a
Brucker AM 250. Chemical shifts are given in parts per
million ;d) down®eld from tetramethylsilane ;TMS) as
internal standard. Coupling constants are given in Hertz
;Hz). Unless otherwise speci®ed deuteriochloroform was
used as a solvent. The following abbreviations are used:
sˆsinglet, dˆdoublet, tˆtriplet, qˆquartet, mˆmultiplet,
ddˆdouble doublet, dtˆdouble triplet. Microanalysis were
obtained using a Carbo Erba MOD11016 instrument. The
term `ether' refers to diethyl ether and petroleum ether
refers to that fraction of petroleum ether with boiling
point between 40 and 608C. Column chromatography was
performed with ¯ash silica gel ;Merck 9385).
The apparently anomalous result with 24 would then be due
to the buttressing effect ;A1,2-strain) of the ortho-methoxy
group enhancing the cyclisation of 40 to the extent that the
stabilising effect of the two methoxy substituents on the
p-participation of the analogue of41 is negated. In order
to test this hypothesis we carried an analogous three-step
sequence on 3-methoxyphenol ;Scheme 10).
5.1. General procedure for the palladium catalysed
alkylation of phenols with allene
Formation of O-dienyl ether 42 occurred in 69% yield using
the conditions described for Table 1. Thermal Claisen
rearrangement over 6 h as described for Table 2 afforded
43 in 42% yield. Cyclisation of 43 using the conditions
described in Table 3 afforded a 4:1 mixture ;63%) of 44
and 45. Thus in the absence of the buttressing effect of the
additional methoxyl group in 24 the isomer ratio from 43
reverts to `normal' 4:1 ratio, indicating 41 does not play a
dominant role in determining the isomer ratio. The phenol
The phenol ;2 mmol) and Pd;PPh3)4 ;5 mol%), or Pd;OAc)2
;5 mol%) and tris-2-furylphosphine ;10 mol%), were mixed
in dry THF ;10 ml) in a Schlenk tube. The solution was
degassed by two freeze-pump-thaw cycles before addition
of allene ;1 bar). The reaction mixture was stirred at 808C
for 16 h, then cooled. The excess pressure was vented from
the Schlenk tube and the reaction mixture was concentrated
in vacuo. The residue was puri®ed by column chromato-
graphy.
Scheme 10.

R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
7973
5.1.1. *3-Methyl-2-methylene-but-3-enyloxy)-benzene *1)
Column chromatography eluting with 49:1 v/v petroleum
ether±ether afforded the product ;64%) as a colourless
amorphous powder, mp 45±468C. ;Found: C, 65.95; H,
6.15; N, 6.15. C12H13NO3 requires: C, 65.75; H, 6.0; N,
6.4%); dH 1.98 ;s, 3H, Me), 4.83 ;s, 2H, OCH2), 5.08,
5.11, 5.36 and 5.39 ;4£s, 4£1H, 2£CvCH2) and 6.99 and
8.29 ;2£d, 2£2H, Jˆ9.3 Hz, ArH); m/z ;%): 219 ;M1, 2.5),
202 ;15), 81 ;97), 79 ;100), 53 ;80), and 41 ;67).
Column chromatography eluting with petroleum ether
afforded the product ;67%) as a colourless oil. ;Found: C,
82.45; H, 8.35. C12H14O requires: C, 82.7; H, 8.1%); dH 1.98
;s, 3H, Me), 4.73 ;s, 2H, OCH2), 5.08, 5.11, 5.35 and 5.39
;4£s, 4£1H, 2£CvCH2), 6.96 ;m, 3H, ArH) and 7.29 ;m,
2H, ArH); m/z ;%): 174 ;M1, 49), 159 ;88), 131 ;40), 94
;61), 79 ;100), 65 ;40), 53 ;68), 41 ;66) and 39 ;67).
5.1.5. 1,3-Dimethoxy-5-*3-methyl-2-methylene-but-3-
enyloxy)-benzene *5)
5.1.2. 1-Methoxy-4-*3-methyl-2-methylene-but-3-enyloxy)-
benzene *2)
Column chromatography eluting with 49:1 v/v petroleum
ether±ether afforded the product ;66%) as a colourless oil.
;Found: C, 71.8; H, 7.8. C14H18O3 requires: C, 71.8; H,
7.75%); dH 1.97 ;s, 3H, Me), 3.78 ;s, 6H, 2£OMe), 4.68
;s, 2H, OCH2), 5.09, 5.1, 5.34 and 5.35 ;4£s, 4£1H,
2£CvCH2), 6.09 ;s, 1H, ArH) and 6.13 ;s, 2H, ArH); m/z
;%):234 ;M1, 82), 219 ;100), 203 ;24), 191 ;39), 167 ;71),
125 ;51), 53 ;44) and 41 ;54).
Column chromatography eluting with 99:1 v/v petroleum
ether±ether afforded the product ;69%) as a colourless oil.
;Found: C, 76.6; H, 7.95. C13H16O2 requires: C, 76.45; H,
7.9%); dH 1.97 ;s, 3H, Me), 3.77 ;s, 3H, OMe), 4.67 ;s, 2H,
OCH2), 5.07, 5.11, 5.34 and 5.37 ;4£s, 4£1H, 2£CvCH2)
and 6.86 ;m, 4H, ArH); m/z ;%): 204 ;M1, 28), 189 ;11),
123 ;100), 109 ;16), 95 ;22) and 41 ;25).
5.1.6. 1,3,5-Tris-*3-methyl-2-methylene-but-3-enyloxy)-
benzene *6)
5.1.3. 4-*3-Methyl-2-methylene-but-3-enyloxy)-benzoic
acid methyl ester *3)
Column chromatography eluting with 99:1 v/v petroleum
ether±ether afforded the product ;33%) as a colourless oil.
;Found: C, 78.9; H, 8.4. C24H30O3 requires: C, 78.65; H,
8.25%); dH 1.97 ;s, 9H, 3£Me), 4.66 ;s, 6H, 3£OCH2),
5.07, 5.09, 5.35 and 5.38 ;4£s, 4£3H, 6£CvCH2) and
6.19 ;s, 3H, ArH); m/z ;%): 367 ;M111, 21), 161 ;39),
145 ;44), 119 ;59), 105 ;69), 93 ;88) and 81 ;100).
Column chromatography eluting with 24:1 v/v petroleum
ether±ether afforded the product ;56%) as a colourless
amorphous powder, mp 42±438C. ;Found: C, 72.3; H,
7.15. C14H16O3 requires: C, 72.4; H, 6.95%); dH 1.9 ;s,
3H, Me), 3.81 ;s, 3H, CO2Me), 4.7 ;s, 2H, OCH2), 5.02 ;s,
2H, CvCH2), 5.29 ;s, 2H, CvCH2), and 6.87 and 7.91
;2£d, 2£2H, ArH); m/z ;%): 232 ;M1, 16), 173 ;59), 121
;68), 93 ;32), 79 ;100), 53 ;71) and 41 ;73).
5.1.7. 3-*3-Methyl-2-methylene-but-3-enyloxy)-pyridine
*7)
5.1.4. 1-*3-Methyl-2-methylene-but-3-enyloxy)-4-nitro-
benzene *4)
Column chromatography eluting with 3:2 v/v petroleum
ether±ether afforded the product ;34%) as a colourless oil.
;Found: C, 75.5; H, 7.35; N, 7.75. C11H13NO requires:
C, 75.4; H, 7.5; N, 8.0%); dH 1.98 ;s, 3H, Me), 4.78 ;s,
2H, OCH2), 5.1 and 5.38 ;2£s, 2£2H, 2£CvCH2),7.24
;m, 2H, ArH) and 8.23 and 8.35 ;2£m, 2£1H, ArH); m/z
;%): 175 ;M1,17), 160 ;16), 79 ;36), 53 ;53), 41 ;48) and 39
;100).

7974
R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
5.1.8. 2-*3-Methyl-2-methylene-but-3-enyloxy)-dibenzo-
furan *8)
N, 6.05. C15H15NO requires: C, 79.95; H, 6.7; N, 6.2%); dH
2.0 ;s, 3H, Me), 5.09 ;s, 2H, OCH2), 5.15, 5.2, 5.35 and 5.44
;4£s, 4£1H, 2£CvCH2), 7.07 ;s, 1H, ArH), 7.37 and 7.56
;2£dd, 2£1H, Jˆ7.5 Hz, ArH), 7.68 and 7.88 ;2£d, 2£1H,
Jˆ7.5 Hz, ArH) and 8.96 ;s, 1H, ArH); m/z ;%): 226
;M111, 100), 225 ;M1, 13), 146 ;56), 117 ;23), 73 ;28)
and 69 ;32).
Column chromatography eluting with 99:1 v/v petroleum
ether±ether afforded the product ;60%) which crystallised
from petroleum ether±ether as colourless plates, mp 74±
758C. ;Found: C, 81.6; H, 6.1. C18H16O2 requires: C, 81.8;
H, 6.1%); dH 2.0 ;s, 3H, Me), 4.81 ;s, 2H, OCH2), 5.1, 5.17,
5.37 and 5.43 ;4£s, 4£1H, 2£CvCH2), 7.08 ;dd, 1H, Jˆ2.6
and 9 Hz, ArH), 7.27±7.51 ;m, 5H, ArH) and 7.89 ;d, 1H,
Jˆ8 Hz, ArH); m/z ;%): 264 ;M1, 26), 249 ;20), 224 ;24),
183 ;100), 155 ;44), 127 ;30).
5.1.12. 3-Isopropenyloxy-isoquinoline *12)
Column chromatography eluting with 9:1 v/v petroleum
ether±ether afforded the product ;19%) as a yellow oil.
;Found: C, 77.95; H, 6.15; N, 7.3. C12H11NO requires: C,
77.8; H, 6.0; N, 7.55%); dH 2.07 ;s, 3H, Me), 4.4 and 4.5
;2£s, 2£1H, CvCH2), 7.2 ;s, 1H, ArH), 7.48 and 7.64
;2£dd, 2£1H, Jˆ7.5 Hz, ArH), 7.76 and 7.95 ;2£d,
2£1H, Jˆ7.5 Hz, ArH), and 9.04 ;s, 1H, ArH); m/z ;%):
186 ;M111, 100), 185 ;M1, 18), 146 ;48), 117 ;21), 73
;72) and 69 ;65).
5.1.9. 1-*3-Methyl-2-methylene-but-3-enyloxy)-naphtha-
lene *9)
5.1.13. 1-Isopropenyloxy-4-nitro-benzene *15)
Column chromatography eluting with hexane afforded the
product ;78%) as a colourless oil. ;Found: C, 85.65; H, 7.3.
C16H16O requires: C, 85.7; H, 7.2%); dH 2.01 ;s, 3H, Me),
4.9 ;s, 2H, OCH2), 5.09, 5.17, 5.4 and 5.51 ;4£s, 4£1H,
2£CvCH2), 6.83 ;dd, 1H, Jˆ1.14, 7.3 Hz, ArH), 7.33±
7.49 ;m, 4H, ArH), 7.8 and 8.3 ;2£m, 2£1H, ArH); m/z
;%): 224 ;M1, 31), 209 ;83), 181 ;10), 144 ;50), 115
;100), 79 ;27), 53 ;27) and 41 ;28).
5.1.10. 2-*3-Methyl-2-methylene-but-3-enyloxy)-naph-
thalene *10)
Column chromatography eluting with 99:1 v/v petroleum
ether±ether afforded the product ;42%) as a yellow oil.
;Found: C, 60.55; H, 5.05; N, 8.05. C9H9NO3 requires: C,
60.35; H, 5.05; N, 7.8%); dH 1.99 ;s, 3H, Me), 4.44 and 4.57
;2£s, 2£1H, CvCH2), 7.12 and 8.23 ;2£d, 2£2H,
Jˆ9.2 Hz, ArH); m/z ;%): 179 ;M1, 100), 139 ;58), 109
;86), 65 ;71) and 43 ;48).
Column chromatography eluting with petroleum ether
afforded the product ;69%) as a colourless amorphous
powder, mp 32±338C. ;Found: C, 85.55; H, 7.25. C16H16O
requires: C, 85.7; H, 7.2%); dH 2.0 ;s, 3H, Me), 4.84 ;s, 2H,
OCH2), 5.11, 5.16, 5.39 and 5.44 ;4£s, 4£1H, 2£CvCH2),
7.16±7.43 ;m, 4H, ArH) and 7.74 ;m, 3H, ArH); m/z ;%):
224 ;M1, 73), 209 ;68), 181 ;29), 157 ;44), 144 ;53), 81
;59), 69 ;100).
5.1.14. 1-*3-Methyl-2-methylene-but-3-enyl)-naphtha-
len-2-ol *16)
5.1.11. 3-*3-Methyl-2-methylene-but-3-enyloxy)-isoqui-
noline *11)
Column chromatography eluting with 9:1 v/v petroleum
ether±ether afforded the product ;50%) as a colourless
amorphous powder, mp 73±748C. ;Found: C, 85.8; H, 7.1.
C16H16O requires: C, 85.7; H, 7.2%); dH 2.03 ;s, 3H, Me),
3.99 ;s, 2H, CH2Ar), 4.54 ;s, 1H, CvCH2), 5.06 ;s, 1H,
OH), 5.17 ;s, 2H, CvCH2), 5.42 ;s, 1H, CvCH2), 7.13
;d, 1H, Jˆ8.7 Hz, ArH), 7.30±7.48 ;m, 2H, ArH) and
Column chromatography eluting with 49:1 v/v petroleum
ether±ether afforded the product ;30%) as a colourless
amorphous powder, mp 47±488C. ;Found: C, 79.9; H, 6.9;

R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
7975
7.69±7.81 ;m, 3H, ArH); m/z ;%): 224 ;M1, 67), 209 ;100),
181 ;42), 157 ;21) and 128 ;29).
5.2. General procedure for Claisen rearrangement of the
dienyl aryl ethers
5.1.15. 5-*3-Methyl-2-methylene-but-3-enyl)-quinolin-6-
ol *17)
The dienyl aryl ether ;0.2 g) was dissolved in N,N-dimethyl-
formamide ;2 ml) and the solution heated at 2058C for
3±48 h in a Schlenk tube. The mixture was then cooled to
room temperature, water ;2 ml) added and the mixture
extracted with ether ;3£). The organic extracts were
combined, dried ;anh. Na2SO4), ®ltered and the ®ltrate
evaporated under reduced pressure. The residue was
puri®ed by ¯ash chromatography to afford the product.
5.2.1. 2-*3-Methyl-2-methylene-but-3-enyl)-phenol *22)
Column chromatography eluting with 7:3 v/v hexane±ethyl
acetate afforded the product ;60%) which crystallised from
ethyl acetate±methanol as colourless prisms, mp 193±
1948C. ;Found: C, 79.7; H, 6.6; N, 6.1. C15H15NO requires:
C, 79.95; H, 6.7; N, 6.2%); dH ;acetone-d6) 2.01 ;s, 3H, Me),
4.03 ;s, 2H, CH2Ar), 4.31, 5.11, 5.16 and 5.49 ;4£s, 4£1H,
2£CvCH2), 7.4 ;dd, 1H, Jˆ4.1, 8.6 Hz, ArH3), 7.5 ;d, 1H,
Jˆ9.1 Hz, ArH7), 7.88 ;d, 1H, Jˆ9.1 Hz, ArH8), 8.1 ;d, 1H,
Jˆ8.6 Hz, ArH4), 8.71 ;d, 1H, Jˆ4.1 Hz, ArH2) and 8.91 ;s,
1H, OH); m/z ;%): 225 ;M1, 45), 210 ;100), 182 ;30), 158
;28), 130 ;34).
Column chromatography eluting with 13:1 v/v petroleum
ether±ether afforded the product ;20%) as a colourless oil.
;Found: C, 81.55; H, 8.2. C12H14O requires: C, 82.7; H,
8.1%); dH 1.9 ;s, 3H, Me), 3.63 ;s, 2H, CH2Ar), 4.91 ;s,
1H, CvCH2), 4.92 ;s, 1H, OH), 5.05 ;s, 1H, CvCH2), 5.2
and 5.23 ;2£s, 2£1H, CvCH2), 6.81±6.89 ;m, 2H, ArH)
and 7.09±7.14 ;m, 2H, ArH); m/z ;%): 173 ;M121, 7), 147
;31), 97 ;59), 83 ;47), 73 ;49), 69 ;63) and 57 ;100).
5.1.16. 10,10-Bis-*3-methyl-2-methylene-but-3-enyl)-
10H-phenanthren-9-one *18)
5.2.2. 4-Methoxy-2-*3-methyl-2-methylene-but-3-enyl)-
phenol *23)
Column chromatography eluting with 99:1 v/v petroleum
ether±ether afforded the product ;53%) as a colourless oil.
;Found: C, 88.0; H, 7.4. C26H26O requires: C, 88.1; H,
7.4%); dH 1.6 ;s, 6H, 2£Me), 2.89 and 3.32 ;2£d, 2£2H,
Jˆ15 Hz, 2£CH2), 4.12, 4.75, 4.8 and 4.89 ;4£s, 4£2H,
4£CvCH2), 7.34 ;m, 4H, ArH), 7.64 ;m, 1H, ArH) and
8.04 ;m, 3H, ArH); m/z ;%): 354 ;M1, 22), 273 ;70), 258
;100), 231 ;68), 251 ;65), 178 ;47) and 41 ;71).
Column chromatography eluting with 16:1 v/v petroleum
ether±ether afforded the product ;44%) as a colourless oil.
;Found: C, 76.3; H, 7.8. C13H16O2 requires: C, 76.45; H,
7.9%); dH 1.96 ;s, 3H, Me), 3.6 ;s, 2H, CH2Ar), 3.75 ;s,
3H, OMe), 4.6 ;s, 1H, OH), 4.91, 5.04, 5.19 and 5.23 ;4£s,
4£1H, 2£CvCH2), and 6.67±6.78 ;m, 3H, ArH); m/z ;%):
204 ;M1,100), 189 ;62), 173 ;13), 147 ;15), 73 ;40) and 57
;34).
5.1.17. 1-Methoxy-3-*3-methyl-2-methylene-but-3-
enyloxy)-benzene *42)
5.2.3. 3,5-Dimethoxy-2-*3-methyl-2-methylene-but-3-
enyl)-phenol *24)
Column chromatography eluting with 4:1 v/v petroleum
ether±ether afforded the product ;69%) as a colourless oil.
;Found: C, 76.25; H, 8.05. C13H16O2 requires: C, 76.45; H,
7.9%); dH 1.97 ;s, 3H, Me), 3.786 ;s, 3H, OMe), 4.70 ;s, 2H,
OCH2), 5.07, 5.10, 5.35 and 5.38 ;4£s, 4£1H, 2£CvCH2),
6.52 ;dd, 1H, Jˆ8.9 and 8.1 Hz, ArH) and 6.50±6.53 ;m,
3H, ArH); m/z ;%): 204 ;M1, 57), 189 ;100), 173 ;15), 161
;44), 124 ;42), 77 ;38) and 41 ;95).
Column chromatography eluting with 9:1 v/v petroleum
ether±ether afforded the product ;62%) as a colourless oil.
;Found: C, 71.75; H, 7. 85. C14H18O3 requires: C, 71.75; H,
7.75%); dH 1.97 ;s, 3H, Me), 3.6 ;s, 2H, CH2Ar), 3.77 ;s,
6H, 2£OMe), 4.87 and 5.06 ;2£s, 2£1H, CvCH2), 5.12 ;s,
1H, OH), 5.2 and 5.29 ;2£s, 2£1H, CvCH2) and 6.11 and
6.12 ;2£s, 2£1H, ArH); m/z ;%): 234 ;M1, 66), 219 ;60),
167 ;100), 73 ;77), 69 ;52) and 55 ;67).

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R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
5.2.4. 1-*3-Methyl-2-methylene-but-3-enyl)-dibenzofuran-
2-ol *25)
in CH2Cl2 ;5 ml) was stirred at room temperature overnight,
then neutralised with sat. NaHCO3 and extracted with
CH2Cl2. The combined organic layers were washed with
water, dried ;anh. Na2SO4) and the solvent removed under
reduced pressure. The residue was puri®ed by column chro-
matography.
5.3.1. 3,3-Dimethyl-2-methylene-2,3-dihydro-1H-benzo-
[f]chromene *27) and 2-isopropenyl-2-methyl-1,2-
dihydro-naphtho[2,1-b] furan *28)
Column chromatography eluting with 16:1 v/v petroleum
ether±ether afforded the product ;56%) as a colourless
amorphous powder, mp 129±1308C. ;Found: C, 81.55; H,
6.25. C18H16O2 requires: C, 81.8; H, 6.1%); dH 2.05 ;s, 3H,
Me), 4.1 ;s, 2H, CH2Ar), 4.66 ;s, 1H, CvCH2), 4.84 ;s, 1H,
OH), 5.18 ;s, 2H, CvCH2), 5.44 ;s, 1H, CvCH2), 6.99 ;d,
1H, Jˆ8.7 Hz, ArH), 7.29 ;m, 1H, ArH), 7.37 ;d, 1H,
Jˆ8.7 Hz, ArH), 7.43 ;m, 1H, ArH), 7.54 ;d, 1H, Jˆ8 Hz,
ArH) and 7.72 ;d, 1H, Jˆ8 Hz, ArH); m/z ;%): 264 ;M1,
100), 249 ;65), 197 ;92), 147 ;32), 135 ;39), 73 ;78) and 57
;68).
Column chromatography eluting with petroleum ether
afforded a 4:1 mixture of ;27) and ;28) ;62%) as a colourless
oil. ;Found: C, 85.6; H, 7.15. C16H16O requires: C, 85.65; H,
7.19%); dH 1.54 ;s, 6H, 2£2-Me), 1.64 ;s, 3H, 20-Me), 1.87
;s, 3H, CH3±Cv), 3.29 and 3.51 ;2£d, 2£1H, Jˆ15.5 Hz,
30-CH2, 3.82 ;s, 2H, 4-CH2), 4.88 ;s, 2H, CvCH2), 5.14 and
5.15 ;2£s, 2£1H, CvCH2) and 7.02±7.81 ;m, 12H, ArH);
m/z ;%): 224 ;M1, 47), 209 ;26), 193 ;8), 181 ;10), 147 ;20),
133 ;14) and 73 ;100).
5.2.5. 2-*3-Methyl-2-methylene-but-3-enyl)-naphthalen-
1-ol *26)
5.3.2. 3,3-Dimethyl-2-methylene-2,3-dihydro-1H-pyrano-
[3,2-f] quinoline *29) and 2-isopropenyl-2-methyl-1,2-
dihydro-furo[3,2-f] quinoline *30)
Column chromatography eluting with 99:1 v/v petroleum
ether±ether afforded the product ;63%) as a colourless
amorphous powder, mp 60±618C. ;Found: C, 85.5; H,
7.25. C16H16O requires: C, 85.7; H, 7.2%); dH 2.0 ;s, 3H,
Me), 3.79 ;s, 2H, CH2Ar), 4.99, 5.08, 5.26 and 5.33 ;4£s,
4£1H, 2£CvCH2), 5.5 ;s, 1H, OH), 7.24 ;d, 1H,
Jˆ3.14 Hz, ArH), 7.39±7.48 ;m, 3H, ArH), and 7.77 and
8.17 ;2£m, 2£1H, ArH); m/z ;%): 224 ;M1, 20), 209 ;100),
194 ;9), 165 ;13) and 128 ;36).
Column chromatography eluting with 7:3 v/v petroleum
ether±ether afforded a 6.5:1 mixture of ;29) and ;30)
;76%) as a colourless oil. ;Found: C, 79.85; H, 6.65; N,
6.4. C15H15NO requires: C, 79.95; H, 6.7; N, 6.2%); dH
1.55 ;s, 6H, 2£2-Me), 1.65 ;s, 3H, 20-Me), 1.88 ;s, 3H,
CH3±Cv), 3.29 and 3.51 ;2£d, 2£1H, 30-CH2), 3.8 ;s,
2H, 4-CH2, 5.0) and 5.16 ;s, 2H, CvCH2) and 7.26, 7.38,
7.91, 8.2 and 8.75 ;5£m, 5£2H, ArH); m/z ;%): 226
;M111, 100), 225 ;M1, 20), 210 ;8), 158 ;8) and 73 ;10).
5.2.6. 5-Methoxy-2-*3-methyl-2-methylene-but-3-enyl)-
phenol *43)
5.3.3. 6-Methoxy-2,2-dimethyl-3-methylene-chroman *31)
and 2-isopropenyl-5-methoxy-2-methyl-2,3-dihydro-
benzofuran *32)
Column chromatography eluting with 4:1 v/v petroleum
ether±ether afforded the product ;42%) as a colourless oil.
;Found: C, 76.95; H, 7.95. C13H16O2 requires: C, 76.45; H,
7.9%); dH 1.95 ;s, 3H, Me), 3.55 ;s, 2H, CH2Ar), 3.75 ;s,
3H, OMe), 4.70 ;s, 1H, OH), 4.90, 5.03, 5.19 and 5.26 ;4£s,
4£1H, 2£CvCH2), 6.44 ;m, 2H, ArH) and 6.93 ;d, 1H,
Jˆ8.2 Hz, ArH); m/z ;%): 204 ;M1, 70), 175 ;35), 137
;100), 77 ;37) and 55 ;24).
5.3. General procedure for acid catalysed cyclisation of
2-*1,3-dienylmethyl) phenols
Column chromatography eluting with 99:1 v/v petroleum
ether±ether afforded a 3.5:1 mixture of ;31) and ;32)
;62%) as a colourless oil. ;Found: C, 76.35; H, 7.95.
A solution of the dienyl phenol ;0.1 g), p-toluenesulfonic
acid monohydrate ;0.5 equiv.), tri¯uoroacetic acid ;0.01 ml)

R. Grigg et al. / Tetrahedron 57 ꢀ2001) 7965±7978
7977
C13H16O2 requires: C, 76.45; H, 7.9%); dH 1.46 ;s, 6H, 2£2-
Me), 1.54 ;s, 3H, 20-Me),1.83 ;s, 3H, CH3±Cv), 2.98 and
3.23 ;2£d, 2£1H, Jˆ15.7 Hz, 30-CH2), 3.5 ;s, 2H, 4-CH2),
3.75 ;s, 6H, 2£OCH3), 4.83 ;s, 1H, CvCH2), 5.0 ;s, 2H,
CvCH2),5.08 ;s, 1H, CvCH2), 6.6±6.76 ;m, 6H, ArH); m/z
;%): 204 ;M1, 34), 189 ;100), 174 ;11), 161 ;8) and 146 ;9).
;s, 3H, CH3±Cv), 3.18 and 3.42 ;2£d, 2£1H, Jˆ15.4 Hz,
30-CH2), 3.65 ;s, 2H, 4-CH2), 4.87, 5.07, 5.09, and 5.17
;4£s, 4£1H, 2£CvCH2), 7.14 ;d, 1H, Jˆ8.4 Hz, ArH),
7.25±7.46 ;m, 7H, ArH), 7.74 ;m, 2H, ArH) and 8.0 and
8.2 ;2£m, 2£1H, ArH); m/z ;%): 224 ;M1, 97), 209 ;100),
181 ;40), 83 ;25), 69 ;49) and 57 ;79).
5.3.4. 5,7-Dimethoxy-2,2-dimethyl-3-methylene-chroman
*33) and 2-isopropenyl-4,2-dimethoxy-2-methyl-2,3-
dihydro-benzofuran *34)
5.3.7. 7-Methoxy-2,2-dimethyl-3-methylene-chroman *44)
and 2-isopropenyl-6-methoxy-2-methyl-2,3-dihydro-
benzofuran *45)
Column chromatography eluting with 49:1 v/v petroleum
ether±ether afforded a 1:1.5 mixture of ;33) and ;34)
;56%) as a colourless oil. ;Found: C, 72.05; H, 7.9.
C14H18O3 requires: C, 71.75; H, 7.75%); dH 1.47 ;s, 6H,
2£2-Me), 1.54 ;s, 3H, 20-Me), 1.81 ;s, 3H, CH3±Cv),
2.89 and 3.11 ;2£d, 2£1H, Jˆ15 Hz, 30-CH2), 3.33 ;s,
2H, 4-CH2), 3.77 ;m, 12H, 4£OCH3), 4.82 ;s, 1H,
CvCH2), 5.02 ;s, 2H, CvCH2), 5.07 ;s, 1H, CvCH2)
and 6.0±6.07 ;m., 4H, ArH); m/z ;%): 234 ;M1, 70), 219
;56), 133 ;65), 97 ;59), 83 ;42), 73 ;44) and 57 ;77).
Column chromatography eluting with hexane afforded a 4:1
mixture of ;44) and ;45) ;63%) as a colourless oil. ;Found:
C, 76.8; H, 8.2. C13H16O2 requires: C, 76.45; H, 7.9%); dH
1.44 ;s, 6H, 2£2-Me), 1.52 ;s, 3H, 20-Me), 1.80 ;s, 3H,
CH3CvC), 3.15 and 3.50 ;2£d, 2£1H, Jˆ14.8 Hz, 30-
CH2), 3.55 ;s, 2H, 4-CH2), 3.81 ;s, 6H, 2£OCH3), 4.85 ;s,
1H, CvCH2), 5.0 ;s, 2H, CvCH2), 5.12 ;s, 1H, CvCH2)
and 6.82±6.60 ;m, 6H, ArH); m/z ;%): 204 ;M1, 100), 189
;85), 161 ;61), 137 ;68) and 41 ;46).
5.3.5. 3,3-Dimethyl-2-methylene-2,3-dihydro-1H-4,7-dioxa-
benzo[c]¯uorene *35) and 2-isopropenyl-2-methyl-1,2-
dihydro-benzo[d]benzo[1,2-b;4,3-b0] difuran *36)
Acknowledgements
We thank Leeds University and the Thailand Research Fund
;TRF) of the Royal Golden Jubilee Project for support.
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ether±ether afforded a 3:1 mixture of ;35) and ;36) ;60%)
as a colourless oil ;Found: C, 82.05; H, 5.95. C18H16O2
requires: C, 81.8; H, 6.1%); dH 1.55 ;s, 6H, 2£2-Me),
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7.2%); dH 1.58 ;s, 6H, 2£2-Me), 1.64 ;s, 3H, 20-Me), 1.86

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