An efficient Benzannulation protocol for the synthesis of 9,9-Diphenyl-9H-fluorenols using Intramolecular Allene Friedel–Crafts Annulation

Article abstract of DOI:10.1002/ejoc.201900895

Herein we report a one-pot cascade benzannulation protocol for the synthesis 9,9-diaryl-9H-fluorenol, a key structure of many important natural products which exhibit the significant biological activities particularly phosphodiesterase-4 (PDE4) inhibitory activity. This approach proceeds through the annulation of tert-propargyl alcohols with 2-methyl acetylacetone through an intramolecular allene Friedel–Crafts reaction using Ca(OTf)₂ as the environmentally benign catalyst. Synthetic transformations of these compounds to useful materials are also presented here with the aid of cross-coupling and RCM reactions.

Full text of DOI:10.1002/ejoc.201900895

A Journal of
Accepted Article
Title: An efficient Benzannulation protocol for the synthesis of 9,9-
diphenyl-9H-fluorenols using Intramolecular-Allene-Friedel-Crafts
Annulation
Authors: SRINIVASARAO YARAGORLA and P. Rajesh
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201900895
Link to VoR: http://dx.doi.org/10.1002/ejoc.201900895
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European Journal of Organic Chemistry
10.1002/ejoc.201900895
An efficient Benzannulation protocol for the synthesis of 9,9-
diphenyl-9H-fluorenols using Intramolecular-Allene-Friedel-Crafts
Annulation
[
a]
[a]
Srinivasarao Yaragorla* and P. Rajesh
Abstract: Herein we report a one-pot cascade benzannulation
protocol for the synthesis 9,9-diaryl-9H-fluorenol, a key structure
of many important natural products which exhibit the significant
biological activities particularly phosphodiesterase-4 (PDE4)
inhibitory activity.This approach proceeds through the annulation
of tert-propargyl alcohols with 2-methyl acetylacetone through
Figure 1. Representative examples of biologically active natural products with
the core structure of fluorenol(first row) and 9,9-diaryl-9H-fluorenol (second
row).
Selanginpulvilins are another group of natural products with 9,9-
diphenyl-9H-fluorenol structure (Figure 1) were isolated, and
interestingl
these
molecules
showed
significant
[5,6]
phosphodiesterase-4 (PDE4) inhibitory activity. Owing to the
unique structural framework and the biological activities
associated with these molecules, the 9,9-diaryl-9H-
fluorenolcorestructure becomes a promising lead for further
exploration of biological properties. In this regard, a few reports
on the total syntheses and a synthetic approach have been
an Intramolecular-Allene-Friedel-Crafts reaction using Ca(OTf)
2
as the environmentally benign catalyst. Synthetic
transformations of these compounds to useful materials are also
presented here with the aid of cross-coupling and RCM
reactions.
[
6-9]
disclosed by various research groups.
research group was engaged in discovering novel synthetic
Past few years, our
[
10]
Introduction
methods for the annulations reactions. Owing to the synthetic
demand of 9,9-diaryl-9H-fluorenols, herein we report a single
9
,9-diphenyl-9H-fluorenol is an important structural motif with a
-5-6 tricyclic framework presented in biologically active natural
step synthesis of 9,9-diphenyl-9H-fluorenols using
a
6
benzannulation protocol. Based on our recent observation that
products. Generally, these structures represent a common name, tert-propargyl alcohols react with 3-methylpentane-2,4-dione
I
fluorene which is a well-established privileged structure owing to
its applications in the fields of material science and the
through
S
N
2
mechanism to yield tetra-substituted allene
[
10a,10b]
intermediates,
we assume that if the aryl group of allene
[
1,2]
2
pharmaceutical industry.
In material science, molecules
(as highlighted in Figure 2), can react with sp carbon of allene
through an intramolecular-Friedel-Crafts annulation(IFCA) in the
presence of a suitable Lewis acid conditions, that can lead to the
benzannulation.
bearing a core structure of fluorene are used as dyes sensitized
solar cells and light emitting diodes due to their unique
properties such as good charge transporters with high chemical
[1]
stability. As mentioned above, their abundance in natural
products is also witnessed by the isolation of fluostatins and
2
R
O
[3,4]
O
pyrazolofluostatins (Figure 1). The fluostatin family of natural
products was reported to have diverse bioactivities including
dipeptidyl peptidases inhibition and antibacterial and antitumor
O
O
Me
Me
R1
MeMe
Me
Me
O
C
O
SN I
R1
R2
Ar
Me
2
[
3]
+
Me
Me
R2
HO
R1
OH
activities. Very recently, pyrazolofluostatins were isolated from
[
4]
Ar
south China sea-derivedmicromonospora rosariaSCSIO N160.
Ar
Ar
H
This work
R2
R1
Me
OH HO
OH HO
H
N
OH
HO
H
N
functionalization
N
N
Figure
2.Synthetic
strategies
from
in
situ
generated
homo-
O
OH
OH
allenylketone(previous and current)
O
O
O
HO
O
HO
RO
OH
OH
fluostatinC (R=H)
fluostatinD (R=COCHMe
2
)
pyrazolofluostatinA
pyrazolofluostatinB
fluostatinF (R=Me)
Results and Discussion
The quest for discovering the suitable reaction conditions for the
synthesis of proposed 9,9-diaryl-9H-fluorenol was commenced
by selecting 3-methylpentane-2,4-dione (1a) and propargyl
alcohol (2a) as the reacting partners to achieve the synthesis of
(3a) via the benzannulation protocol. Initially,1a (1.3equiv.) and
2a (1 equiv.) were heated directly (neat condition) with
OH
OH
OH
OHC
R
OCH
3
OCH3
OH
OCH
3
OCH3
OH
HO
OH)
selanginpulvilinB (R=CHO)
selanginpulvilinC (R=CH
selanginpulvilinD (R=H)
HO
HO
selanginpulvilinA (R=CH
2
selanginpulvilinK
selanginpulvilinL
[10-11]
o
Ca(OTf)
diphenyl-9H-fluorenol 3a was formed in 47% yield after 3 h
entry 1, Table 1).To increase the reaction yield,we thought that
2
/Bu
4
NPF
6
(10/5 mol%)
at 90 C, as expected 9,9-
3
)
(
a solvent medium could help and hence refluxed the reaction in
acetonitrile (polar aprotic) for 2.5 h, and the reaction proceeded
to yield 55% of 3a, then the solvent was switched to ethanol
(polar protic solvent) but there was no reaction in ethanol.
Toluene (nonpolar solvent), gave 45% yield of 3a (entries 2-4,
table 1).1,2-dichloroethane as the solvent medium gave 85%
yield of 3a (entry 5, Table 1). Further attempts to improve the
[
a] Dr. Srinivasarao Yaragorla (corresponding author)
Mr. P. Rajesh
School of Chemistry, Gurbaksh Building, W-16, 17, University of
Hyderabad, P.O. Central University, Gachibowli, Hyderabad,
5
000046, Telangana State, India.
E-mail: srinivas.yaragorla@uohyd.ac.in
Home page: https://sites.google.com/view/srinivasarao-yaragorla
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.201900895
[
13]
yield of 3a by an increase or decrease of the catalyst
combined yield (Scheme 1). Similarly, the reaction yielded the
mixture of regioisomers 3q-3t with the meta-substituted aryl ring
of 2 (Scheme 1). The rationale for the formation of regioisomers
can be explained by careful observation of these annulated
products obtained in Table 2 and Scheme 1.
loadingswere unsuccessful. Alternative catalysts were also
explored like TsOH (10 mol%), FeCl
mol%), but all of them yielded moderate to poor yields (entries 8-
0). Therefore entry 5 (Table 1) was considered as the optimum
3
(10 mol%), and TfOH (10
1
reaction condition for the synthesis of 3a (85% yield) from 1a
and 2a.
Table 2. Synthesis of 9,9-diphenyl-9H-fluorenols through a
Ca(II)-catalyzed Intramolecular-Allene-Friedel-Crafts Annulation
[
a]
R1
Table 1.Optimization of the reaction conditions.
HO
Me
R2
Ca(OTf)2/Bu4NPF6
O
Ar
10/5 mol%
R1
HO
+
Ar
R3
O
Me
R3
,2-DCE, 90 o
C
R2
1
Me
1
2
3
Me
Me
Me
HO
HO
HO
En
try
Reaction conditions.
Yield
Me
[
b]
(%)
Me
Me
o
1
2
Ca(OTf)
2
/Bu
4
NPF
6
6
(10/5 mol%), neat, 90 C, 3 h
47
55
Me
Me
Ph Ph
Ph Ph
Ph Ph
o
Ca(OTf)
2
/Bu
4
NPF
(10/5 mol%), MeCN, 90 C,
3a[7] (85%, 2.5 h)
3b[7] (75%, 3 h)
3c (75%, 2.5 h)
2.5 h
o
Me
3
4
Ca(OTf)
2
/Bu
4
NPF
6
6
(10/5 mol%), EtOH,90 C,2.5 h nr
HO
Me
Me
o
HO
HO
Ca(OTf)
2
/Bu
4
NPF
(10/5 mol%), toluene, 100 C,
45
85
2.5 h
[
5
c]
o
Ph
OEt
Ca(OTf)
2
/Bu
/Bu
/Bu
4
4
4
NPF
NPF
NPF
6
6
6
(10/5 mol%) DCE, 90 C, 2.5
Me
Cl
Ph
h
Me
Me
Ph Ph
Ph Ph
o
6
Ca(OTf)
2
(10/10 mol%), DCE, 90 C,
85
3d (76%, 2.5 h)
3e (74%, 2.5 h)
2.5 h
o
7
8
9
1
1
Ca(OTf)
Ca(OTf)
2
(5/10 mol%), DCE, 90 C, 3 h
67
20
69
10
28
3f (74%, 2.5 h)
Me
Me
o
HO
HO
2
/KPF
6
(10/5 mol%), DCE, 90 C, 6 h
Me
HO
o
TsOH (10 mol%) DCE, 90 C, 3.5 h
o
Me
0
1
TfOH (10 mol%) DCE, 90 C, 10 h
Me
o
FeCl
3
(10 mol%) DCE, 90 C, 10 h
Me
Cl
Me
Ph
Ph
[
[
a]
c]
[b]
Me
Mixture of 1a (1.3 equiv.), 2a (1 equiv.) were used; Isolated yields;
Ph
Optimum conditions; DCE: 1,2-dichloroethane; rt: room temperature;
TsOH:p-toluenesulfonic acid; TfOH: triflic acid; nr: no reaction
F
F
3
i (76%, 2.5 h)
3g (77%, 3 h)
3h (78%, 2.5 h)
After establishing the optimum reaction conditions for the
synthesis of 3a, we aimed to generalize this protocol to check
the viability of various substituents on the reactants (Table 2).
Therefore we subjected 1a with various propargyl alcohols (2)
bearing alkyl substitutions on aryl ring under the optimized
Me
Me
Me
HO
HO
HO
Me
Me
Me
Ph
Me
Ph
reaction conditions and obtained the corresponding fluorenols
n
3
b (7-methyl) and 3c(7-butyl ) in good yields. Similarly, fluorenol
d was made with C7-phenyl substitution and 3e with C7-ethoxy
F
3
F
MeO
MeO
substitution.This protocol was also tolerated the propargylic-
3
j (76%, 3 h
3k (76%, 3 h)
3l (80%, 2.5 h)
phenyl substitutions (on substrate 2) and gave the fluorenols 3f,
3h and 3j with p-chloro, p-fluoro and p-methoxy groups in good
yields. Fluorenol 3l was made which is bearing both the phenyl
groups with p-fluoro substitutions at the quaternary centre.
Products 3g, 3i, 3k indicate that the protocol offers to have more
than one substitution on reactant 2. When the aryl moiety of
propargyl alcohol 2 was taken as phenanthrenyl, it has given the
product 3m in good yield. Next, we thought to change the methyl
substitution on diketone (1a) and hence synthesized the
Me
HO
HO
HO
Me
Me
Me
Ph Ph
Me
Ph Ph
3o (55%, 3 h)
Ph Ph
3n[7] (48%, 3 h)
3m (75%, 3 h)
[
12]
diketone bearing a benzyl group on active methylene carbon
1b) and treated with propargyl alcohols under standard
Since Friedel-Crafts annulation proceeds through the C-C bond
formation from ortho carbon, we will have three situations for this
benzannulation reaction, based on the substitutions of the aryl
ring (ortho, para and meta). For instance, consider the case-1, of
the para-substituted aryl ring, it has two equivalent ortho
carbons, so it doesn't matter which carbon will form the ring,
thus a single product will be obtained (Case 1, Scheme 1) and it
(
conditions to obtain the respective fluorenols 3n and 3o in
moderate yields (Table 2). When we treated 1a with propargyl
alcohol
2 bearing a 3-methyl on the aryl group (meta
substitution) under the same conditions, the reaction yielded a
I
mixture of two regioisomers 3p:3p in 1:0.2 ratio with a 76%
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European Journal of Organic Chemistry
10.1002/ejoc.201900895
is evidenced by the synthesis of 3b-3e, 3g, 3i, 3k and 3o. On
the otherhand, when we have an ortho-substitution on aryl ring
Our attempts to isolate the in situ generated homo-allenyl ketone,
which we believed as the key intermediate in this
benzannulation reaction, were successful. We were able to
isolate allenes 4a-4e in excellent yields in a short reaction time
(Table 3). To support that the allene 4a is the intermediate for
(case 2), there is only one carbon to undergo IFCA reaction, and
hence we got a single product (3m). The third case is that a
meta-substitution on the aryl group of 2, where we will have two
reactive carbons (ortho and para) to give two regio-isomeric
products through IFCA (3p-3t, Scheme 1). Ofcourse, the reason
for the unequal isomeric distribution can be explained based on
the steric hindrance.
the synthesis of 3a, we refluxed
a
mixture of 4a and
and
Ca(OTf) /Bu NPF (under optimum conditions) for 1 h
2
4
6
obtained 3a in 85% yield. Noteworthy, allene 4c did not react as
expected, because the cyclopropyl ring cannot offer IFCA
reaction. Based on these observations we proposed the reaction
mechanism as depicted in Scheme 2. Initially, the enol of
2OHR3
R
R1
R1
Me
HO
2 4 6
/Bu NPF
HO
diketone (1) reacts with activated tert-propargyl alcohol 2
Ca(OTf)
0/5 mol%
R
+
O
+
I
1
R1
through S
N
2 mechanism to yield the allenyl ketone 4 (isolated
Ar
Ar
O
,2-DCE, 90 o
C
and confirmed). Next, allene 4 undergoes an intramolecular-
Friedel-Crafts annulation (IFCA) to give the tricarbocyclic
compound 5. Owing to the ring strain of fused cyclobutane,
compound 5 further cycloisomerizes to furnish indene derivative
1
Me
Me
R2 R3
Me
R2 R3
R
1
Ar
2
3
R
3'
Me
Me
HO
Me
Me
Me
HO
HO
Me
HO
6. Diketone 6 readily underwent an intramolecular-aldol
annulation and gives the -hydroxy ketone 8. Finally, elimination
followed by aromatization of aldol adduct 8 gives the fluorenol 3.
Me
Me
Ph
Me
Me
Me
Ph Ph
Me
Ph Ph
Ph
I
3
p:3p (1:0.2) 76%, 3 h
MeO
Ca2+
Me
MeO
HO
Me
I
3
s:3s (1:0.4) 73%, 3 h
O
O
Me
HO
OH
O
allene formation
via S
2I
Allene-Friedel-Crafts
annulation
2
Me
Bn
N
R3 Me
HO
Me
HO
Me
Me
R2
Bn
R3
C
Me
Me
2
-H O; -Ca(II)
Ph
R
R2
1
R1
Me
1
HO
Ph
4
Ca(OTf)
Me
Ph Ph
X
Me
Me
Ph Ph
HO
R
3
Me
Me
X
I
R3
X=Cl; 3q:3q (1:0.6) 75%, 2.5 h
R3
O
3
t:3t' (1:0.3) 50%, 3 h
cyclo-
isomerization
I
O
Ca
X=F; 3r:3r (1:0.5) 78%, 2.5 h
Ca+
Me
Me
O
Me
O
Me
Me
R1
R2 R1
O
R
2
O
O
R Me
Ar
O
R3
O
Me R1 R2
O
R3
O
2+Ca
R2
R3
R1
5
R1
6
7
C
C
Me
C
Me
R1
R2
3
R2
R
R3
H
R3
para center
relativelyless steric
majorisomer
O
O
O
HO
Ar
Ar
elimination
enolization/
aromatization
-
intra-aldol
ortho center
more steric
R
R
-H
2
O
-
minor isomer
Me
R1 R2
-Ca(II)
Me
R1 R2
Me
R1 R2
Case 1-para-substitued Aryl
equivalentortho carbons
no isomer formation
Case 2-ortho-substitued Aryl
only one ortho carbon to react
-no isomer formation
+Ca
Case 3-meta-substitued Aryl
one ortho, one para carbon to react
regioisomerformation
8
-
9
3
-
Scheme 2. Mechanism
Intramoecular Allene-Friedel-Crafts-Annulation(AFCA)
Scheme 1. The schematic explanation for the formation of regioisomeric
fluorenols
Further, we have emphasized on few important synthetic
transformations of these fluorenols, for which we selected 3a as
the precursor. Initially, 3a was subjected to o-allylation with allyl
Table 3. Synthesis of tetrasubstituted allenes using Ca(OTf)
2
O
C
O
R1
bromide and K CO to give olefin 10, which was then undergone
2
3
O
O
o
R2
HO
Ca(OTf)
2 4 6
/Bu NPF
Me
Me
a [3,3] Claisen rearrangementat 180 C gave the ortho-allylation
of 3a, the crude compound was further allylated to get diene
10/5 mol%
Me
R1
Me
Me
Me
R3
1,2-DCE, 90 oC, R2
Me
1
[14]
40 min
intermediate 11. Ring-closing metathesis (RCM) of diene 11
2
R3
4
nd
[15]
with Grubbs 2 generation catalyst gave the benzoxepine
O
C
O
O
C
O
O
O
Cl
fused indene 12 in 71% yield (Scheme 3).
Me
Ph
Me Cl
Me Me
Me
Me
Me
i) Toluene,180 oC, 24 h
Claisen rearrangement)
Me
Ph
Me
Me
OH
O
2 3
K CO (2.5 equiv)
(
Ph Ph
C
allyl bromide (1.2 eq)
Ph
Ph
Ph
Acetone, reflux
4 h, 81%
ii) K CO , (2.5 equiv),
2 3
allyl bromide (1.2 equiv)
acetone, reflux, 3 h, 61%
Ph
Ph
Ph Me
Ph Me
4a (92%)
4b (88%)
4c
(
75%)
3a
10
O
O
O
O
NO2
Me
Me
Me
C
Me
Me
Me
O
Me
Ph
Me
Ph
O
Grubbs-II, (5 mol%)
Toluene, reflux
C
Cl
Ph
4e (85%)
Ph
Ph Me
Ph Ph Me
5
h, 71%
1
2
11
4
d (90%)
Scheme 3. Synthesis of flrouenoxepine (12)
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European Journal of Organic Chemistry
10.1002/ejoc.201900895
Fluorenol 3a was also subjected to o-nitration with
cericammonium nitrate to get o-nitro-fluorenol 13 in 62% yield; it
is noteworthy that the aryl ring is now fully substituted in 13.
Propargylation of 3a was also achieved with propargyl bromide
Ethylacrylate (2.5 eq),
Pd(OAC)2 (5 mol%),
Me
OMe
OEt
K CO /Bu NBr (2.5 eq/ 1 eq)
2 3 4
DMF, 80 oC, 22 h, 76%
O
Ph
Ph Me
2 3
and K CO to furnish compound 14 in 78% yield (Scheme 4).
Heck cross-coupling
2
0
Next, we planned a sequence of reactions on 3a, that is
bromination followed by Heck or Sonogashira cross-coupling
reactions. Accordingly, 3a was brominated with NBS and
obtained o-bromo phenol 16 in 69% yield. Encouraged by this
result, we attempted a Heck coupling with ethyl acrylate.
Unfortunately, we found that the reaction did not proceed, then
we tried a Sonogashira coupling with phenyl acetylene, which
also did not proceed. Therefore we tried to install an ortho-iodide
functionality on 3a by treating with NIS and thus obtained o-
iodophenol 15 in 74% yield. However, the cross-coupling
reactions of iodide 15 were also failed to react under Heck and
Sonogashira conditions (Scheme 4).
Me
Me
OMe
OMe
I
Me SO4 (2 eq)
2
NIS (1 eq), CHCl3
2 3
K CO (2.5 eq)
3a
0 oC, 12 h, 79%
7
Ph Ph Me
acetone, reflux,
3 h, 81%
Ph
Ph Me
1
8
1
7
Sonogoshira
cross-coupling
Me
OMe
Phenylacetylene (2 eq)
Pd(OAc) (5 mol%)
Ph DABCO(3 eq)
CH CN, rt, 12 h, 61%
2
Ph
Ph Me
3
1
9
nitration
Me
Me
OH
OH
NO2
Scheme 5. Cross-coupling reactions of 3a
Ce(NH ) (NO )
3 6
4
2
(
2 equiv),
H
NaHCO (1.1 equiv)
3
Me
dry-acetonitrile, rt, 4 h
Me
Conclusion
Ph Ph
Ph Ph
3a
1
3(62%)
In conclusion, we have developed
a
simple one-pot
propargylation
Me
benzannulation protocol for the synthesis of privileged structure,
,9-diphenyl-9H-fluorenols from simple starting materials.
Besides, this protocol offers to synthesize tetracyclic allenes.
The reaction is catalyzed by eco-friendly catalyst Ca(OTf) and
Me
9
OH
O
Br
(1.5 equiv)
2
K
2
CO , (2.5 equiv)
3
Ph
Ph Me
yielded the products in good to excellent yields. Synthetic
transformations of the fluorenols such as nitration,
propargylation, bromination, iodination and fluorenoxepine
synthesis have been developped. Further developments on this
intramolecular-allene-Friedel Crafts annulation are currently
ongoing in our laboratory.
Me
Ph Ph
acetone, reflux, 6 h
1
4 (78%)
3
a
Me
bromination
OH
Br
NBS
1.1 equiv)
Sonogashira &
Heck conditions
no
reaction
(
3
a
DCM, rt, 2 h
Me
Ph Ph
1
6 (69%)
Experimental Section
Me
iodination
NIS, (1 equiv)
OH
Sonogashira &
Heck conditions reaction
no
General information: Unless otherwise noted, all reagents were used as
3
a
I
CHCl
3
, 70 oC, 12 h
received from commercial suppliers. Ca(OTf)2 and Bu NPF6 were
4
Me
obtained from Sigma-Aldrich and used without further purification.
Ph Ph
Reactions were performed in flame-dried or oven-dried glassware with
magnetic stirring. Reactions were monitored using thin-layer
chromatography (TLC) with aluminium sheets silica gel 60 F254 from
Merck. TLC plates were visualized with UV light (254 nm), iodine
treatment. Column chromatography was carried out using silica gel 60-
120 mesh as the stationary phase. NMR spectra were recorded at 500
MHz and 400 MHz (H) and 125 MHz and 100 MHz (C), respectively on
Avance Bruker spectrometer. Chemical shifts (δ) are reported in ppm,
1
5 (74%)
Scheme 4. Synthetic transformations of 3a (propargylation, nitration,
bromination and iodination). Conditions: Heck (ethyl acrylate (2.5 equiv.),
o
Pd(OAc)
2
(5 mol%), Bu
4
NBr (1 equiv.), K
2
CO
3
(2.5 equiv.), DMF, 80 C, 24 h;
2
Sonogashira(Phenylacetylene (2 equiv.), Pd(OAc) (5 mol%), DABCO (3
equiv), acetonitrile, rt, 24 h)
We presume that free hydroxyl group of 3a might be playing a
3
using the residual solvent peak in CDCl (H: δ = 7.26 and C: δ = 77.0
role to inhibit the cross-coupling reaction, therefore we made a
[
14]
ppm) as an internal standard, and coupling constants (J) are given in Hz.
methyl ether of 3a by treating with dimethyl sulfate (17), and
[
16]
Melting points were measured with LABINDIA mepa melting apparatus.
then subjected to iodination with NIS and obtained iodide 18
in good yield. Though we are not sure of the exact reason at the
moment, as presumed the iodide 18 underwent a smooth cross-
coupling reaction under Heck conditions and gave the desired
Experimental procedure for the synthesis of 1,4-dimethyl-9,9-
diphenyl-9H-fluoren-3-ol (3a):To a mixture of 1 (0.35mmol) and 1,3-
dicarbonyl compound 2 (0.45mmol) in DCE (2 mL), Ca(OTf) /Bu NPF
2 4 6
o
[
17]
(10/5 mol%) was added. The reaction was stirred at 90 C, and the
completion of the reaction was monitored by TLC. After completion of the
reaction, the solvent was removed under reduced pressure,and the
residue was purified by silica gel column chromatography using EA/PE
product 20
phenylacetylene was also successfully yielded 19 (Scheme
in 76% yield. Sonogashira coupling of 18 with
[
18]
5).
(
3
10:90, v/v) to obtain the desired product 3a in 85% yield.Compounds 3a,
b and 3n are reported earlier.
[
7]
Experimental procedure for the synthesis of 3-methyl-3-(1,3,3-
triphenylpropa-1,2-dien-1-yl)pentane-2,4-dione(4a): To amixture of 1
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.201900895
1
3
(
0.35mmol) and 1,3-dicarbonyl compound 2 (0.45mmol) in DCE (2 mL),
Ca(OTf) /Bu NPF (10/5 mol%) was added. The reaction was stirred at
C, for 30-40 min and was stopped after formation of allene (monitor
1H), 4.92 (s, 1H), 2.69 ( s, 3H), 1.89 (s, 3H) ;ppm; C NMR(125 MHz,
CDCl ): δ 155.7, 153.4, 142.7, 142.4, 141.0, 140.5, 133.8, 129.1, 127.9,
2
4
6
3
o
9
0
127.3, 127.1, 126.4, 125.4, 123.2, 116.9, 64.5, 20.0, 12.3 ppm; IR
by TLC), solvent was removed under reduced pressure, and the resultant
residue was purified by silica gel column chromatography using EA/PE
(film):νmax3524, 3022, 2923, 1589, 1491, 1298, 1246, 1183, 1073, 912
−
1
cm ; HRMS (ESI-TOF): m/z calcd for C27H22O [M+H]+ : 363.1751,
(10:90, v/v) to obtain the desired product 4a in 92% yield.
found: 363.1750.
General experimental procedure for the synthesis of 2-allyl-3-
allyloxy)-1,4-dimethyl-9,9-diphenyl-9H-fluorene (11) To stirring
solution of 1,4-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (100 mg, 0.27
mmol) in anhydrous acetone (5.0 mL) were added K CO (87 mg,
.633mmol) and allylbromide (26 µL, 0.33 mmol), the resulting reaction
1,4,7-trimethyl-9,9-diphenyl-9H-fluoren-3-ol (3b)Yield: 93 mg (75%)
o
1
(
a
white solid; mp 252-254 C; H NMR (CDCl , 500 MHz): δ 7.80 (d, J=8Hz,
3
1H), 7.28-7.24 (m, 4H), 7.22-7.17 (m, 8H), 7.13-7.08 (m, 2H), 6.43 (s,
13
2
3
1H), 4.73 (s, 1H), 2.62 (s, 3H), 2.26 (s, 3H), 1.82 (s, 3H) ppm;
C
0
NMR(125 MHz, CDCl ): δ 155.9, 153.4, 142.9, 142.4, 140.1, 138.5,
3
o
mixture was heated at 80 C for 3 h. After completion of the reaction, it
was filtered through short plug of celite and the filtrate was
137.2, 133.7, 129.2, 128.1, 127.9, 126.4, 126.1, 122.9, 116.7, 116.4,
a
64.4, 21.7, 19.9, 12.3 ppm; IR (film): ν 3531, 2921, 2851, 1736, 1587,
max
−
1
concentrated under reduced pressure to give crude compound which
was purified by silica gel column chromatography to afford the allyl ether.
The above obtained above allyl etherwas dissolved in toluene (2 mL)
1446, 1309, 850 cm ; (LCMS): m/z [M+H]+ : 377.
o
7-butyl-1,4-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (3c) Yield: 92 mg
and placed in a sealed pressure tube and heated at 180 C for 24 h. The
o
1
(
75%) white solid; mp 248-249 C; H NMR (CDCl
3
, 500 MHz): δ 7.81 (d,
reaction mixture was directly purified by silica gel column
chromatography to afford the rearranged allyl compound.
J=7.0 Hz, 1H), 7.25 (m, 5H), 7.18 (m, 5H), 7.11 (m, 2H), 6.44 (s, 1H),
4
.68 (s, 1H), 2.62 (s, 3H),2.52 (t, J=8.0 Hz, 2H), 1.83 (s, 3H), 1.48 (m,
13
3
2H), 1.25 (m, 2H), 0.85 (t, J=7.0 Hz, 3H) ppm; C NMR (CDCl , 125
General experimental procedure for the synthesis of 6,12-dimethyl-
MHz): 155.9, 153.4, 143.0, 142.4, 142.3, 140.7, 138.6, 133.8, 129.2,
7
(
,7-diphenyl-5,7-dihydro-2H-fluoreno[3,2-b]oxepine (12) 2-allyl-3-
allyloxy)-1,4-dimethyl-9,9-diphenyl-9H-fluorene (11, 100 mg, 0.22 mmol)
was dissolved in dry toluene (4 mL) and heated to reflux before adding
127.9, 127.3, 126.4, 125.6, 122.9, 116.7, 116.4, 64.5, 35.8, 33.7, 22.4,
2
0.0, 14.0, 12.3 ppm; IR (film): νmax 3531, 2920, 2852, 1736, 1587, 1446,
−1
nd
1310 cm ; HRMS (ESI-TOF): m/z calcd forC31H30O[M+H]+ :419.5772,
2
1
generation Grubbs catalyst (9 mg, 5 mol%). Reaction was stirred at
o
00 C for 6 h. After completion of the reaction, it was cooled to room
found: 419.5769
.
temperature, and passed through a silica gel (20% EtOAc/Hexanes) and
concentrated. The residual oil was further purified by flash
chromatography (silica gel, gradient elution, 3-4% EtOAc/Hexanes) to
afford the desired product 12 in 71% yield.
1
,4-dimethyl-7,9,9-triphenyl-9H-fluoren-3-ol (3d) Yield: 92 mg (76%)
o
1
white solid; mp 250-251 C; H NMR (CDCl
3
, 500 MHz): δ 7.98 (d, J=6.5
Hz, 1H), 7.49 (m, 4H), 7.37 (t, J=7.5 Hz, 2H), 7.30 (m, 5H), 7.23 (m, 6H),
13
6
.48 (s, 1H), 4.73 (s, 1H), 2.67 (s, 3H), 1.86 (s, 3H) ppm; C NMR
General experimental procedure for the synthesis of 2-iodo-1,4-
dimethyl-9,9-diphenyl-9H-fluoren-3-ol (15) To a solution of compound
(
CDCl , 125 MHz): 156.5, 142.8, 142.7, 141.3, 140.3, 140.2, 133.9, 129.2,
3
1
2
1
28.8, 128.0, 127.3, 127.2, 126.5, 126.2, 124.2, 123.4, 117.1, 117, 64.7,
1
,4-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (100 mg, 0.27 mmol) in CHCl
3
0, 12.4 ppm; IR (film): νmax 3397, 3056, 2923, 2851, 1733, 1598, 1490,
(6 mL) was added catalytic TsOH followed by the addition of N-
−1
385, 1075, 1031 cm
26
; HRMS (ESI-TOF): m/z calcd forC33H O
iodosuccinimide (61 mg, 0.22 mmol). The reaction mixture was heated
at 55 °C for 16 h. After completion of the reaction, the reaction mixture
[M+H]+ : 439.2064, found: 439.2060.
was quenched with saturated aqueous NaHCO
with CH Cl (20 mL x 3). The collected organic fractions were dried over
anhydrous Na SO and concentrated under vacuum to afford a white
solid compound which was forwarded to the next step without further
3
(25 mL) and extracted
7
-ethoxy-1,4-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (3e) Yield: 91 mg
2
2
o 1
(74%) white solid; mp 246-247 C; H NMR (CDCl
J=8.5 Hz, 1H), 7.26 (d, J=7.5 Hz, 5H),7.19 (m, 5H), 6.83 (m, 2H), 6.40 (s,
H), 4.72 (s, 1H), 3.94 (m, 2H), 2.60 (s, 3H), 1.82 (s, 3H) 1.32 (t, J=7.0
3
, 500 MHz): δ 7.81 (d,
2
4
1
purificationand characterization
.
13
Hz, 3H) ppm; C NMR (CDCl
3
, 125 MHz): 158.7, 157.6, 153.4, 142.9,
42.1, 140.5, 134.0, 129.2, 128.0, 126.4, 123.9, 116.1, 115.8, 113.1,
12.1, 64.5, 63.6, 20.0, 14.9, 12.3 ppm; IR (film):νmax3551, 3517, 2975,
1
1
1
General experimental procedure for the synthesis of 3-methoxy-1,4-
dimethyl-9,9-diphenyl-9H-fluorene (17) To a stirring solution of 1,4-
dimethyl-9,9-diphenyl-9H-fluoren-3-ol (100 mg, 0.27 mmol) in anhydrous
−1
603,1490,1291,1091, 854, 754cm
; HRMS (ESI-TOF): m/z calcd
26 2
forC29H O
[M+H]+ : 407.2013, found: 407.2010.
acetone (10.0 mL) were added K
2
CO (76.0 mg, 0.55 mmol) and Me SO
3
2
4
o
(58 µL, 0.55 mmol).The resulting reaction mixture was heated at 80
C
9
9
7
4
1
1
-(4-chlorophenyl)-1,4-dimethyl-9-phenyl-9H-fluoren-3-ol (3f) Yield:
2 mg (74%) white solid; mp 179-180 C; H NMR (CDCl
.92 (d, J=7.5 Hz, 1H), 7.30 (t, J=7.5 Hz, 2H), 7.20 (m, 10H), 6.47 (s, 1H),
3
.75 (s, 1H), 2.64 (s, 3H), 1.83 (s, 3H) ppm; C NMR (CDCl ,125 MHz):
55.3, 153.6, 142.2, 142.1, 141.5, 141.0, 133.7, 132.3, 130.6, 129.0,
27.5, 127.3, 126.3, 126.7, 125.3, 117.4, 117.0, 64.1, 20.0, 12.3 ppm; IR
for 3 h. After completion of the reaction, it was filtered through a short
plug of celite,and the filtrate was concentrated in rotavapor and purified
by silica gel column chromatography to afford the methoxy protected
compound as white solid.
o 1
3
, 500 MHz): δ
13
Experimental procedure for Sonogashira cross-coupling of 18 to 19:
Pd(OAc) (2 mol%) was dissolved in MeCN (1 mL), and was added to a
2
mixture of phenylacetylene (45 mg, 0.45 mmol),9 (100 mg, 0.19 mmol),
DABCO (3 equiv.), and MeCN (4 mL). Then the mixture was stirred
−
1
(
(
film):νmax3386, 2923, 2358, 1693, 1487, 1353, 1295, 1090 cm ; HRMS
ESI-TOF): m/z calcd for C27 21ClO [M+H]+ : 397.1361,found: 397.1362.
H
under N
2
at room temperature for 12 h. The resulting mixture was filtered
9-(4-chlorophenyl)-1,4,7-trimethyl-9-phenyl-9H-fluoren-3-ol
Yield: 95 mg (77%) white solid; mp 180-181 C; H NMR (CDCl , 500
MHz): δ 7.79 (d, J=6.5 Hz, 1H), 7.20 (m, 9H), 7.09 (d, J=9.0 Hz, 2H),
(3g)
o
1
off, washed andthe filtrate was extracted with diethyl ether. The
combined organic layers were washed with brine and dried over
3
anhydrous Na
2
SO
4
.
The solvent was evaporated under reduced
6.42 (s, 1H), 4.81 (s, 1H), 2.60 (s, 3H), 2.26 (s, 3H), 1.81 (s, 3H) ppm;
C NMR (CDCl , 125 MHz): 155.5, 153.6, 142.4, 142.0, 141.7, 140.6,
3
13
pressure,and the residue was purified by columnchromatography (2–4%,
EtOAc in pet ether) with silica gel to give product 14in 61% yield.
138.4, 137.4, 133.6, 132.2, 130.6, 129.0, 128.2, 128.0, 126.6, 126.0,
23.0, 117.0, 116.6, 64, 21.7, 20, 12.3 ppm; HRMS (ESI-TOF): m/z calcd
forC28H23ClO [M+Na]+ : 433.1334,found: 433.1333.
1
Experimental procedure for Heck reaction of 18 to 20:Ethyl acrylate
(
49.8 mg, 0.49 mmol), was added to a solution of (100 mg, 0.19 mmol)
in DMF (1.8 mL) containing K CO (2.5 equiv.) and Bu NBr (1 equiv.) and
stirred at room temperature for 5 min. Pd(OAc) (5 mol %) was then
added, and the flask was flushed with N , sealed and allowed to stir at 80
2
3
4
9
-(4-fluorophenyl)-1,4-dimethyl-9-phenyl-9H-fluoren-3-ol (3h) Yield:
2
o 1
3
98 mg (78%) white solid; mp 193-194 C; H NMR (CDCl , 500 MHz): δ
2
o
7.92 (d, J = 7.5 Hz, 1H), 7.24 (t, J = 2 Hz, 2H), 7.24-7.15 (m, 8H), 6.88 (t,
C for 22 h. The resulting mixture was filtered off, washed and the filtrate
was extracted with diethyl ether. The combined organic layers were
J = 9 Hz, 2H), 6.46 (s, 1H), 4.83 (s, 1H) 2.63 (s, 3H), 1.83 (s, 3H) ppm;
13
3
C NMR (CDCl , 125 MHz): δ 162.5, 160.6, 155.6, 153.5, 142.5, 140.5,
2 4
washed with brine and dried over anhydrous Na SO . The solvent was
1
40.4, 138.5, 138.5, 133.7, 130.7, 130.7, 129.1, 128.1, 127.4, 127.2,
evaporated under reduced pressure, and the residue was purified by
columnchromatography (6–8%, EtOAc in pet ether) with silica gel to give
product in 76% yield.
126.6, 125.3, 123.3, 117.3, 117.1, 114.8, 114.6, 63.9, 19.9, 12.3 ppm; IR
−1
(film):νmax3398, 3057, 2925, 1705, 1503, 1297, 1226, 1077, 831 cm
;
HRMS (ESI-TOF): m/z calcd for C27
H21FO [M+H]+ : 381.1656,found:
381.1655.
1
,4-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (3a) Yield: 108 mg (85%)
o 1
white solid; mp 205-206 C; H NMR (CDCl
3
, 500 MHz): δ 7.97 (d, J =8Hz,
1H), 7.38 (d, J =7.5Hz, 1H), 7.32-7.24(m, 5H), 7.23-7.20 (m, 7H), 6.50 (s,
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.201900895
9
9
7
6
3
1
1
1
-(4-fluorophenyl)-1,4,7-trimethyl-9-phenyl-9H-fluoren-3-ol(3i) Yield:
9-(4-chlorophenyl)-1,4,6-trimethyl-9-phenyl-9H-fluoren-3-ol
Yield: 92 mg (75%) white solid; mp 161-164 C; H NMR (CDCl
MHz): δ 7.73 (s, 1H), 7.22 (m, 3H), 7.19 (m, 6H), 7.16 (m, 1H), 7.00 (m,
(3q)
, 500
o
1
o
1
3
4 mg (76%) white solid; mp 202-203 C; H NMR (CDCl , 500 MHz): δ
3
.79 (d, J=7.0 Hz, 1H), 7.23 (m, 5H), 7.18 (m, 2H), 7.00 (d, J=5 Hz, 2H),
.88 (m, 2H), 6.42 (s, 1H), 4.78 (s, 1H), 2.61 (s, 3H), 2.26 (s, 3H), 1.81 (s,
1H), 6.47 (s, 1H), 4.72 (s, 1H), 2.64 (s, 3H), 2.40 (s, 3H), 1.83 (s, 3H)
13
13
H) ppm; C NMR (CDCl
3
, 125 MHz): 162.5, 160.6, 155.8, 153.5, 142.7,
3
ppm; C NMR (CDCl , 125 MHz): 153.6, 152.7, 142.5, 142.4, 141.7,
42.2, 140.5, 138.7, 138.6, 138.3, 137.3, 133.6, 130.8, 130.7, 129.0,
28.2, 128.0, 126.5, 126.0, 123.0, 116.9, 116.5, 114.7, 114.6, 63.8, 21.7,
9.9, 12.3 ppm; (LCMS): m/z [M+H]+ : 395.
141.1, 140.6, 136.9, 133.7, 132.2, 130.7, 129.0, 128.4, 128.0, 127.9,
126.6, 125.0, 124.0, 117.3, 117.0, 63.7, 21.8, 20.0, 12.4 ppm; (LCMS):
m/z [M+H]+ : 411.
9
9
7
1
-(4-methoxyphenyl)-1,4-dimethyl-9-phenyl-9H-fluoren-3-ol (3j) Yield:
9-(4-fluorophenyl)-1,4,6-trimethyl-9-phenyl-9H-fluoren-3-ol (3r) Yield:
97 mg (78%) white solid; mp 177-179 C; H NMR (CDCl , 500 MHz): δ
3
7.73 (s, 1H), 7.20 (m, 9H), 6.99 (d, J=7.0 Hz, 1H),6.87 (d, J=6.5 Hz, 1H),
o
1
o
1
3
4 mg (76%) white solid; mp 208-209 C; H NMR (CDCl , 500 MHz): δ
.90 (d, J=7.5 Hz, 1H), 7.27 (m, 4H), 7.18 (m, 6H), 6.75 (m,2H), 6.46 (s,
13
H), 4.82 (s, 1H), 3.74 (s, 3H), 2.63 (s, 3H), 1.84 (s, 3H) ppm; C NMR
,125 MHz): 158.1, 156.0, 153.4, 143.0, 142.6, 140.9, 140.4, 134.5,
6.45 (s, 1H), 4.80 (s, 1H), 2.64 (s, 3H), 2.39 (s, 3H), 1.82 (s, 3H) ppm;
13
(CDCl
3
3
C NMR (CDCl , 125 MHz): 156.5, 142.8, 142.7, 141.3, 140.3, 140.2,
1
1
1
33.7, 130.2, 129.0, 127.9, 127.3, 127.0, 126.4, 125.3, 123.2, 117.1,
133.9, 129.2, 128.8, 128.0, 127.3, 127.2, 126.5, 126.2, 124.2, 123.4,
117.1, 117.0, 64.7, 20.0, 12.4 ppm;HRMS (ESI-TOF): m/z calcd
17.0, 63.9, 55.3, 20.0, 12.3 ppm; IR (film):νmax3370, 2947, 2359, 1736,
−
1
603, 1505, 1233, 1146, 1098, 1022, 827 cm ; HRMS (ESI-TOF): m/z
[M+H]+ : 393.1856,found: 393.1858.
forC28H23FO [M+H]+ : 395.1813,found:395.1813.
24 2
calcd for C28H O
9
-(4-methoxyphenyl)-1,4,6-trimethyl-9-phenyl-9H-fluoren-3-ol
o
1
9
-(4-methoxyphenyl)-1,4,7-trimethyl-9-phenyl-9H-fluoren-3-ol
(3k)
, 500
3
(3s)Yield: 90 mg (73%) as white solid; mp 137-138 C; H NMR (CDCl ,
o
1
Yield: 92 mg (75%) white solid; mp 210-211 C; H NMR (CDCl
3
500 MHz): δ 7.26-7.24 (m, 3H), 7.22-7.14 (m, 6H), 6.99-6.97 (m, 1H),
MHz): δ 7.82 (d, J=8.0 Hz, 1H), 7.51 (m, 1H), 7.20 (m, 11H), 6.78 (m, 2H),
6.75-6.73 (m, 2H), 6.43 (s, 1H), 4.90 (s, 1H), 3.73 (s, 3H), 2.63 (s, 3H),
2.38 (s, 3H), 1.83 (s, 3H) ppm; C NMR (CDCl , 125 MHz): δ 158.1,
3
13
13
6.46 (s, 1H), 4.77 (s, 1H),3.78 (s, 3H), 2.64 (s, 3H), 2.30 (s, 3H) ppm;
C
NMR (CDCl
3
, 125 MHz): 158.1, 156.2, 153.4, 143.2, 142.6, 140.5, 138.3,
153.3, 153.3, 143.2, 142.9, 141.1, 140.4, 136.5, 134.8, 133.7, 130.3,
130.2, 129.1, 129.1, 128.2, 127.9, 127.7, 126.3, 124.9, 123.9, 117.1,
116.7, 113.2, 113.1, 63.5, 53.3, 21.8, 19.9, 12.4 ppm; IR (film): νmax 3371,
1
1
1
4
37.2, 134.8, 133.7, 130.3, 129.1, 128.8, 128.7, 127.9, 126.3, 126.0,
24.4, 123.0, 119.8, 116.7, 116.4, 114.9, 113.2, 63.7, 55.3, 21.7, 12.3,
0.9 ppm; HRMS (ESI-TOF): m/z calcd forC29
07.2013,found:407.2013.
−
1
26
H O
2
[M+H]+:
2947, 2359, 1736, 1603, 1505, 1233, 1098, 1022 cm ; HRMS (ESI-
TOF): m/z calcd forC29 [M+H]+ : 407. 2013,found:407. 2015.
26 2
H O
9
,9-bis(4-fluorophenyl)-1,4-dimethyl-9H-fluoren-3-ol (3l) Yield: 99 mg
4-benzyl-1,6-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (3t) Yield: 76 mg
o 1
o
1
(80%) white solid; mp 236-237 C; H NMR (CDCl
3
, 500 MHz): δ 7.93 (d,
3
(50%) white solid; mp 188-190 C; H NMR (CDCl , 500 MHz): δ 7.43-
J =7.5 Hz, 1H), 7.31-7.25 (m, 3H), 7.21-7.19 (m, 5H), 6.91-6.87 (m, 3H),
7.41 (m, 1H), 7.32-7.30 (m, 7H), 7.27-7.20 (m, 9H), 7.05-7.03 (m, 1H),
6.55 (s, 1H), 4.83 (s, 1H), 4.58 (s, 2H), 3.30 (s, 3H), 2.25 (s, 3H) ) ppm;
C NMR (CDCl , 125 MHz): δ 155.8, 154.2, 142.9, 142.6, 141.1, 140.2,
3
13
6.49 (s, 1H), 4.77 (s, 1H), 2.64 (s, 3H), 1.83 (s, 3H) ppm; C NMR
13
(
CDCl , 125 MHz): δ 162.8, 161.7, 155.4, 153.6, 142.1, 140.8, 140.3,
3
1
1
38.2, 133.5, 130.6, 130.5, 127.5, 127.4, 125.2, 123.4, 117.4, 117.1,
14.9, 114.7, 63.3, 20.1, 12.3 1 ppm; HRMS (ESI-TOF): m/z calcd
139.2, 135.2, 129.8, 129.1, 128.8, 128.6, 128.2, 128.1, 127.6, 127.3,
126.5, 126.3, 125.4, 123.1, 119.2, 117.4, 64.5, 37.5, 31.7, 20.1 ppm; IR
−
1
forC27
20 2
H F O [M+H]+ : 399. 4518, found: 399. 4516
(film):νmax3526, 3021, 2923, 1598, 1449, 1377, 1069, 743 cm ; HRMS
ESI-TOF): m/z calcd for C34 28O [M+H]+: 453. 2218, found:453. 2218.
(
H
9
,12-dimethyl-13,13-diphenyl-13H-indeno[1,2-l]phenanthren-10-ol
o
1
(3m) Yield: 90 mg (75%) white solid; mp237-238 C; H NMR (CDCl
3
,
3-methyl-3-(1,3,3-triphenylpropa-1,2-dien-1-yl)pentane-2,4-dione
o 1
5
00 MHz): δ 8.68-8.33 (m, 3H), 7.67-7.57 (m, 7H), 7.39-7.18 (m, 8H),
(4a)Yield: 123 mg (92%) white solid; mp 121-123 C; H NMR (CDCl
3
,
13
6.54 (s, 1H), 4.93 (s, 1H), 2.59 (s, 3H), 2.07 (s, 3H) ppm; C NMR
, 125 MHz): δ 154.8, 149.5, 145.4, 140.4, 135.7, 132.8, 131.6,
500 MHz): δ 7.43-7.38 (m, 8H), 7.35-7.33 (m, 6H), 7.29-7-26 (m, 1H),
2.20 (s, 6H), 1.68 (s, 3H) ppm; C NMR (CDCl , 125 MHz): δ 207.3,
3
13
(CDCl
3
1
1
31.5, 129.7, 128.4, 128.1, 127.7, 126.9, 126.7, 126.1, 126.1, 126.1,
25.7, 125.2, 123.3, 123.3, 123.1, 116.1, 60.5, 19.9, 17.2 ppm; HRMS
207.1, 135.4, 134.1, 128.7, 128.7, 128.3, 127.9, 127.7, 127.5, 114.1,
109.9, 68.7, 27.9, 20.2 ppm; IR (film): νmax 3081, 1987, 1955, 1697, 1443,
−
1
(ESI-TOF): m/z calcd for C35
H26O [M+H]+ : 463.2064, found: 463.2063.
1202, 722 cm ; HRMS (ESI-TOF): m/z calcd forC27
24 2
H O [M+H]+ :
380.1776, found:380.1780.
4
-benzyl-1-methyl-9,9-diphenyl-9H-fluoren-3-ol (3n) Yield: 74 mg
3-(3-(3,4-dichlorophenyl)-1,3-diphenylpropa-1,2-dien-1-yl)-3-
methylpentane-2,4-dione (4b) Yield: 111 mg (88%) white solid; mp 125-
o
1
(
48%) white solid; mp150-152 C; H NMR (CDCl
3
, 400 MHz): δ 7.24-7.20
o
1
(m, 7H), 7.18-7.12 (m, 10H), 7.05-6.93 (m, 3H), 6.46 (s, 1H), 4.79 (s, 1H),
3
127 C; H NMR (CDCl , 500 MHz): δ 7.46 (t, J = 2 Hz, 1H), 7.39 (d, J =
13
4
1
1
1
3
3
.49 (s, 2H), 3.20 (s, 3H) ppm; C NMR(125 MHz, CDCl ): δ 155.8,154.2,
6.5 Hz, 2H), 7.35-7.33 (m, 3H), 7.32-7.27 (m, 3H), 7.26-7.24 (m, 4H),
13
42.8, 142.6, 140.9, 140.2, 139.2, 136.2, 135.1, 129.8, 129.7, 129.1,
29.1, 128.8, 128.6, 128.4, 128.2, 128.1, 127.6, 127.3, 127.1, 126.5,
25.4, 123.9, 119.2, 117.4, 64.5, 37.5, 28.5 ppm; IR (film): νmax 3523,
3
2.16 (s, 6H), 1.64 (s, 3H) ppm; C NMR (CDCl , 125 MHz): δ 207.2,
206.9, 135.9, 134.6, 133.8, 133.1, 133.1, 130.7, 130.1, 129.1, 128.9,
128.4, 128.3, 128.2, 127.7, 127.6, 112.3, 110.8, 69.1, 27.9, 20.4 ppm;
−
1
021, 2924, 1590, 1489, 1378, 1225, 1136, 868 cm ; (LCMS): m/z
HRMS
(ESI-TOF):
m/z
calcd
2
forC27H22Cl O
2
[M+H]+
:
[M+H]+ : 439.
448.0997,found:448.0998.
4
-benzyl-1,7-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (3o) Yield: 83 mg
3-(1-cyclopropyl-3,3-diphenylpropa-1,2-dien-1-yl)-3-methylpentane-
o 1
o
1
(55%) white solid; mp 137-138 C; H NMR (CDCl
3
, 400 MHz): δ 7.56 (d,
2,4-dione (4c)Yield: 104 mg (75%) white solid; mp 123-125 C; H NMR
(CDCl , 400 MHz): δ 7.35-7.31 (m, 5H), 7.29-7.25 (m, 5H), 2.15 (s, 6H),
1.62 (s, 3H), 1.12 (d, J = 5.2 Hz, 1H), 0.82 (t, J = 2.4 Hz, 2H), 0.56 (t, J
J = 8 Hz, 1H), 7.31 (d, J = 1.6 Hz, 1H) 7.29 (t, J = 8 Hz, 2H), 7.27-7.25
3
(m, 4H), 7.23-7.19 (m, 8H), 7.11 (s, 1H), 6.94 (t, J = 8 Hz, 1H), 6.48 (s,
13
13
1H), 4.72 (s, 1H), 4.54 (s, 2H), 2.20 (s, 3H), 1.87 (s, 3H) ppm; C NMR
= 2 Hz, 2H) ppm; C NMR (CDCl
3
, 100 MHz): δ 207.1, 201.5, 136.1,
(
CDCl
3
, 100 MHz): δ 156.1, 154.2, 142.8, 141.1, 139.3, 137.5, 137.5,
128.5, 128.1, 127.6, 115.1, 111.8, 69.8, 27.5, 19.2, 10.5, 8.4 ppm; IR
−
1
1
1
1
35.1, 129.2, 128.8, 128.2, 128.2, 128.1, 126.4, 126.2, 126.1, 122.7,
18.8, 116.9, 64.3, 31.7, 21.6, 20.1 ppm; IR (film): νmax 3528, 3028, 2360,
489, 1378, 1225, 1029, 802 cm
(film): νmax 3052, 2086, 2044, 1713, 1372, 1086, 740 cm ; HRMS (ESI-
TOF): m/z calcd forC24 [M+H]+ : 344.1776, found:344.1780.
24 2
H O
−
1
; HRMS (ESI-TOF): m/z calcd
forC34
H
28O [M+H]+ : 453. 2218,found:453. 2218.
3
-(2-(9H-fluoren-9-ylidene)-1-phenylvinyl)-3-methylpentane-2,4-
o 1
dione(4d)Yield: 120 mg (90%) white solid; mp 121-124 C; H NMR
(CDCl , 500 MHz): δ 7.77 (d, J = 8 Hz, 2H), 7.64 (d, J = 7.5 Hz, 2H),
7.41-7.38 (m, 2H), 7.33-7.30 (m, 2H), 7.29-7.25 (m, 5H), 2.38 (s, 6H),
1.67 (s, 3H) ppm; C NMR (CDCl , 125 MHz): δ 206.6, 204.9, 139.3,
3
137.1, 133.7, 128.9, 128.7, 128.4, 128.1, 127.5, 123.4, 120.5, 115.1,
1,4,6-trimethyl-9,9-diphenyl-9H-fluoren-3-ol (3p) Yield: 95 mg (76%)
3
o
1
white solid; mp 140-143 C; H NMR (CDCl
3
, 500 MHz): δ 7.73 (s, 1H),
13
7
1
.25 (m, 3H), 7.18 (m, 8H), 6.99 (d, J=8.0 Hz, 1H), 6.46 (s, 1H), 4.70 (s,
H), 2.65 (s, 3H), 2.39 (s, 3H), 1.84 (s, 3H) ppm; C NMR (CDCl
13
3
, 125
MHz): 153.4, 153.1, 143.0, 141.2, 140.6, 136.6, 133.8, 129.3, 129.1,
109.8, 69.3, 27.8, 20.6 ppm; HRMS (ESI-TOF): m/z calcd
1
1
3
28.3, 127.9, 127.8, 126.4, 125.1, 123.9, 117.1, 116.8, 64.2, 21.8, 20.0,
22 2
forC27H O [M+H]+ :378.1620, found: 378.1621.
2.4 ppm; HRMS (ESI-TOF): m/z calcd for
77.1827,found:377.1828.
28 24
C H O [M+H]+ :
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.201900895
3
-(3-(2-chloro-5-nitrophenyl)-1,3-diphenylpropa-1,2-dien-1-yl)-3-
3-methoxy-1,4-dimethyl-9,9-diphenyl-9H-fluorene (17) Yield: 83 mg
o
1
methylpentane-2,4-dione (4e) Yield: 107 mg (85%) white solid; mp 128-
3
(81%) white solid; mp 229-230 C; H NMR (CDCl , 400 MHz): δ 7.94 (d,
o
1
130 C; H NMR (CDCl
3
, 500 MHz): δ 8.26 (d, J = 3 Hz, 1H), 8.21-8.19
J = 7.6 Hz, 1H), 7.33 (d, J = 7.6 Hz, 1H), 7.29-7.26 (m, 5H), 7.21-7.13 (m,
13
(m, 2H), 7.64 (d, J = 8.5 Hz, 2H), 7.38-7.31 (m, 3H), 7.30-7.24 (m, 5H),
7H), 6.54 (s, 1H), 3.84 (s, 3H), 2.63 (s, 3H), 1.91 (s, 3H) ppm; C NMR
(CDCl , 100 MHz): δ 157.5, 155.6, 142.8, 141.9, 141.2, 140.1, 133.4,
13
2
2
1
.2 (s, 3H), 2.18 (s, 3H), 1.67 (s, 3H) ppm; C NMR (CDCl
06.6, 206.5, 146.8, 141.3, 136.2, 133.4, 133.4, 131.1, 129.2, 128.9,
28.4, 127.9, 126.5, 124.3, 112.2, 109.9, 69.1, 28.1, 27.5, 20.5 ppm;
3
, 125 MHz): δ
3
129.1, 127.9, 127.3, 127.1, 126.4, 125.4, 123.4, 119.6, 112.5, 64.5, 56.1,
20.5, 12.2 ppm; IR (film): νmax 2923, 1597, 1491, 1349, 1168, 743, 644
−
1
HRMS (ESI-TOF): m/z calcd for
27
C H22ClNO
4
[M+H]+ :459.1237,
cm ; HRMS (ESI-TOF): m/z calcd for C28
24
H O
[M+H]+ : 377.4975
found:459.1228.
found: 377.4973.
2
-iodo-3-methoxy-1,4-dimethyl-9,9-diphenyl-9H-fluorene (18) Yield:
3
-(allyloxy)-1,4-dimethyl-9,9-diphenyl-9H-fluorene (10) Yield: 87 mg
o 1
1
105 mg (79%) white solid; mp 224-225 C; H NMR (CDCl
3
, 500 MHz): δ
(79%) yellow sticky compound; H NMR (CDCl
3
, 500 MHz): δ 7.34-7.29
7.90 (d, J = 8 Hz, 1H), 7.32-7.29 (m, 2H), 7.27-7.25 (m, 4H), 7.24-7.17
(m, 3H), 7.27-7.25 (m, 4H), 7.22-7.15 (m, 7H), 6.55 (s, 1H), 6.15-6.09 (m,
13
(m, 7H), 3.82 (s, 3H), 2.76 (s, 3H), 2.1 (s, 3H) ppm; C NMR (CDCl
3
,
1
3
1
1
H), 5.49-5.47 (m, 1H), 5.30-5.28 (m, 1H), 4.56-4.55 (m, 2H), 2.67 (s,
H), 1.90 (s, 3H) ppm; C NMR (CDCl , 125 MHz): δ 156.6, 155.7, 142.8,
3
42.3, 141.2, 140.2, 134.1, 133.4, 129.2, 127.9, 127.3, 127.1, 126.4,
25.5, 123.4, 120.1, 117.1, 114.1, 69.8, 64.6, 20.4, 12.4 ppm; IR (film):
13
100 MHz): δ 158.1, 155.4, 146.5, 142.1, 140.8, 140.1, 137.5, 129.1,
128.1, 127.9, 127.3, 126.7, 125.6, 124.4, 123.4, 101.4, 65.6, 60.7, 26.8,
14.6 ppm; IR (film): νmax 2923, 2852, 2096, 1492, 1445, 1374, 1033,
−
1
−
1
745 cm ; HRMS (ESI-TOF): m/z calcd for C28
found: 502. 0793.
H23IO [M+H]+ : 502.0794
ν
max 2923, 1649, 1597, 1450, 1350, 1169, 1032, 906 cm ; (LCMS): m/z
[M+H]+ : 403.
3
-methoxy-1,4-dimethyl-9,9-diphenyl-2-(phenylethynyl)-9H-fluorene
o 1
2
6
7
-allyl-3-(allyloxy)-1,4-dimethyl-9,9-diphenyl-9H-fluorene (11) Yield:
(
5
(
19) Yield: 57 mg (61%) white solid; mp 216-218 C; H NMR (CDCl
00 MHz): δ 7.90 (d, J = 7.5 Hz, 1H), 7.52 (d, J = 6.5 Hz, 1H), 7.36-7.31
m, 5H), 7.29-7.25 (m, 5H), 7.24-7.20 (m, 7H), 3.82 (s, 3H), 2.77 (s, 3H),
3
,
o 1
3
6 mg (61%) white solid; mp 226-228 C; H NMR (CDCl , 400 MHz): δ
.88 (d, J = 7.6 Hz, 1H), 7.33-7.28 (m, 4H), 7.27-7.21 (m, 5H), 7.20-7.14
13
(m, 4H), 6.18-6.11 (m, 2H), 5.96-5.89 (m, 1H), 5.51-5.47 (m, 1H), 5.30-
2
1
1
3
.08 (s, 3H) ppm; C NMR (CDCl , 125 MHz): δ 158.1,155.4, 146.5,
42.1, 140.8, 140.1, 137.5, 132.6, 129.3, 129.1, 128.5, 128.1, 127.9,
27.3, 126.7, 125.6, 124.4, 123.4, 101.4, 65.6, 60.7, 26.8, 14.6 6 ppm;
5
1
1
1
1
.27 (m, 1H), 4.97-4.94 (m, 1H), 4.93-4.78 (m, 1H), 4.33 (d, J = 5.2 Hz,
H), 3.44-3.42 (m, 2H), 2.69 (s, 3H), 1.83 (s, 3H) ppm; C NMR (CDCl ,
3
00 MHz): δ 156.1, 155.5, 146.1, 142.7, 141.1, 138.5, 137.1, 134.2,
33.4, 131.1, 129.2, 129.1, 127.9, 127.5, 127.1, 127.1, 126.4, 125.4,
24.1, 122.9, 116.9, 114.8, 65.1, 31.4, 16.6, 13.9 ppm; HRMS (ESI-
13
HRMS (ESI-TOF): m/z calcd for C36
28
H O
[M+H]+ : 477.2220 found:
477.2219.
TOF): m/z calcd for C33H30O [M+Na]+ : 465.2195, found: 465.2194.
(
E)-ethyl3-(3-methoxy-1,4-dimethyl-9,9-diphenyl-9H-fluoren-2- o
yl)acrylate (20) Yield: 71.4 mg (76%) white solid; mp 230-231 C;
NMR (CDCl , 400 MHz): δ 7.95-7.88 (m, 2H), 7.37-7.33 (m, 6H), 7.32-
7.20 (m, 7H), 6.52 (d, J = 16.4 Hz, 1H), 4.29-4.24 (m, 2H), 3.74 (s, 3H),
1
H
3
6
,12-dimethyl-7,7-diphenyl-5,7-dihydro-2H-fluoreno[3,2-b]oxepine
o 1
13
(
12) Yield: 71 mg (66%) white solid; mp 178-179 C; H NMR (CDCl
3
,
3
2.74 (s, 3H), 2.19 (s, 3H), 1.33 (t, J = 7.2 Hz, 3H) ppm; C NMR (CDCl ,
5
7
2
00 MHz): δ 7.87 (d, J = 8 Hz, 1H), 7.30-7.18 (m, 6H), 7.17-7.14 (m, 6H),
100 MHz): δ 207.1, 167.6, 158.1, 155.9, 146.3, 142.2, 141.5, 140.3,
140.1, 133.8, 129.1, 128.1, 127.9, 127.2, 127.1, 126.6, 125.5, 124.6,
123.5, 123.2, 65.2, 60.6, 60.4, 31.1, 18.1, 14.4, 13.3 ppm; IR (film): νmax
.11 (d, J = 1 Hz, 1H), 5.83-5.81 (m, 1H), 5.43-5.41 (m, 1H), 4.62 (t, J =
13
.5 Hz, 2H), 3.44-3.42 (m, 2H), 2.68 (s, 3H), 1.88 (s, 3H) ppm; C NMR
, 125 MHz): δ 156.5, 155.4, 145.9, 142.8, 141.1, 137.9, 136.2,
−
1
(CDCl
3
2984, 2921, 2850, 1708, 1621, 1567, 1443, 1416, 1297, 1003 cm
HRMS (ESI-TOF): m/z calcd for C33 [M+H]+ : 475.2275 found: 475.
275.
;
30 3
H O
1
2
8
4
29.1, 127.9, 127.1, 126.9, 126.4, 126.2, 125.3, 123.4, 122.7, 70.6, 65.2,
5.8, 16.9, 12.8 ppm; IR (film): νmax 3020, 2922, 1595, 1491, 1156, 1023,
03 cm ; HRMS (ESI-TOF): m/z calcd for C31
14.1984 found: 414.1983.
2
−
1
26
H O
[M+H]+ : calcd
1
,4-dimethyl-2-nitro-9,9-diphenyl-9H-fluoren-3-ol (13) Yield: 69 mg Acknowledgements
o
1
(62%) yellow solid; mp 158-160 C; H NMR (CDCl
3
, 500 MHz): δ 10.47
(
7
s, 1H), 8.04 (d, J = 8.5 Hz, 1H), 7.36-7.34 (m, 2H), 7.30-7.25 (m, 7H),
.25-7.23 (m, 4H), 2.75 (s, 3H), 2.12 (s, 3H) ppm; C NMR (CDCl , 125
3
The authors acknowledge the funding from SERB-India project no-
EMR/2016/4812. Mr. Ankit Kumar is acknowledgedfor the technical help
13
MHz): δ 157.1, 153.3, 145.9, 142.4, 141.8, 138.6, 135.5, 130.6, 129.8,
28.8, 128.2, 127.9, 127.6, 127.1, 125.8, 124.9, 120.6, 65.2, 29.8, 18.7
ppm; (LCMS): m/z [M+H]+ : 406.
,4-dimethyl-9,9-diphenyl-3-(prop-2-yn-1-yloxy)-9H-fluorene
1
Keywords:Allene-Friedel-Crafts annulation, Cycloisomerization,
Fluorenols, propargyl alcohols, Calcium catalysis.
1
(14)
, 400
o
1
Yield: 85.8 mg (78%) white solid; mp 192-193 C; H NMR (CDCl
3
MHz): δ 7.94 (d, J = 7.6 Hz, 1H), 7.34-7.30 (m, 1H), 7.29-7.24 (m, 5H),
7
2
1
1
1
.22-7.15 (m, 7H), 6.65 (s, 1H), 4.71 (d, J = 2.4 Hz, 2H), 2.65 (s, 3H),
.52 (t, J = 2.4 Hz, 1H), 1.92 (s, 3H) ppm; C NMR (CDCl , 100 MHz): δ
3
13
References
55.8, 155.6, 142.1, 142.7, 141.1, 140.4, 133.5, 129.2, 127.9, 127.4,
27.1, 126.5, 125.5, 123.4, 120.5, 114.4, 79.3, 75.3, 64.6, 57.1, 20.4,
2.5 ppm; IR (film): νmax 3060, 2859, 2128, 1596, 1491, 1367, 1156, 1102
1.
a) M. Zeng, T. E. Ballard, A. Tkachenko, V. Burns, D. Feldheim, C.
Melander, Bioorg. Med. Chem. Lett. 2006, 16, 5148-5151; b) Y. Han, A.
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Wood, L. Kelland, S. Neidle, J. Med. Chem.1999, 42, 2679-2684.
−
1
cm ; HRMS (ESI-TOF): m/z calcd for C30
found: 401.1905.
24
H O
[M+H]+ : 401.1907
2-iodo-1,4-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (15) Yield: 99.7 mg
o 1
(74%) white solid; mp 215-216 C; H NMR (CDCl
3
, 400 MHz): δ 7.94 (d,
J = 7.6 Hz, 1H), 7.32-7.26 (m, 7H), 7.22-7.19 (m, 6H), 5.5 (s, 1H), 2.76 (s,
2.
(a) J. Tan, Z. Wang, J. Yuan, Y. Peng, Z. Chen, Adv. Synth. Catal.
2019, 361, 1295-1300. b) T. Hadizad, J. Zhang, Z. Y. Wang, T. C.
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C. Chao, F.-C. Fang, C.-T. Lee and Y.-C. Peng, Org. Lett., 2006, 8,
13
3
1
1
3
H), 2.0 (s, 3H) ppm; C NMR (CDCl , 100 MHz): δ 155.5, 152.6, 142.9,
42.4, 140.5, 140.4, 135.8, 129.1, 128.7, 128.1, 127.9, 127.3, 126.6,
25.5, 123.5, 117.3, 95.9, 65.3, 26.7, 14.1 ppm; HRMS (ESI-TOF): m/z
calcd for C27H21IO [M+H]+ : 488.0637 found: 488.0636
2
-bromo-1,4-dimethyl-9,9-diphenyl-9H-fluoren-3-ol (16) Yield: 83 mg
o
1
(69%) yellow solid; mp 188-190 C; H NMR (CDCl
3
, 400 MHz): δ 7.94 (d,
J = 7.6 Hz, 1H), 7.31 (d, J = 8.4 Hz, 1H), 7.28-7.25 (m, 6H), 7.22-7.19 (m,
1
415–1418.
13
6
H), 5.80 (s, 1H), 2.74 (s, 3H), 2.01 (s, 3H) ppm; C NMR (CDCl
MHz): δ 155.5, 150.2, 142.9, 142.4, 140.3, 139.9, 132.3, 129.1, 128.1,
27.8, 127.3, 126.6, 125.5, 123.4, 118.2, 114.4, 65.3, 20.8, 13.6 ppm;
HRMS (ESI-TOF): m/z calcd for [M-H]+
39.0756,found:439.0755.
3
, 125
3.
a) T. Akiyama, K. T. Nakamura, Y. Takahashi, H. Naganawa, Y.
Muraoka, T. Aoyagi, T.J. Takeuchi, Antibiot. 1998, 51, 586-588; b) Z.
Feng, J. H. Kim, S. F. Brady,J. Am. Chem. Soc. 2010, 132, 11902-
1
27
C H21BrO
:
11903; c) C. Yang, C. Huang, W. Zhang, Y. Zhu, C. Zhang, Org. Lett.
4
2
015, 17, 5324-5327
.
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.201900895
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Yuan, Y. Zhu, Org. Lett. 2017, 19, 592-595; b) W. Zhang, Z. Liu, S. Li,
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6
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7
.
.
L.-F. Yao, D. Tan, X. Miao, K.-W. Huang, RSC Adv.2012, 2, 7594- 7598.
a) A. C. Grimsdale, K. Leok Chan, R. E. Martin, P. G. Jokisz and A. B.
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European Journal of Organic Chemistry
10.1002/ejoc.201900895
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Benzannulation of allenyl ketones*
Srinivasarao Yaragorla* and P. Rajesh
Page No. – Page No.
An efficent Benzannulation protocol
for the synthesis of 9,9-diphenyl-9H-
fluorenols using Intramolecular-
Allene-Friedel-Crafts Annulation
A one-pot synthesis of 9,9-diphenyl-9H-fluorenols is developped from tert-propargyl alcohols and substituted-acetylacetones using Ca(II) salt
in good to excellent yields. This benzannulation reaction involves the formation of allenyl-ketone and a subseqent Allene-Friedel-Crafts
Annulation.
This article is protected by copyright. All rights reserved.