Organocatalytic Asymmetric Domino Michael/Acyl Transfer Reaction Between α-Nitroketones and in situ-Generated ortho-Quinone Methides: Route to 2-(1-Arylethyl)phenols

Article abstract of DOI:10.1002/adsc.201801015

An organocatalytic asymmetric domino Michael/acyl transfer reaction between α-nitroketones and o-quinone methides is disclosed. o-Quinone methides are generated in situ from 2-sulfonylmethylphenols in basic medium. With 10 mol% of bifunctional squaramide catalyst, high yields and excellent enantioselectivities are achieved for a variety of O-acyl 2-(1-arylethyl)phenols under mild reaction condition. (Figure presented.).

Full text of DOI:10.1002/adsc.201801015

Title: Organocatalytic Asymmetric Domino Michael/Acyl Transfer
Reaction Between α-Nitroketones and in situ-Generated ortho-
Quinone Methides: Route to 2-(1-Arylethyl)phenols
Authors: Subhas Pan, Chandan Gharui, and Debasmita Behera
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Adv. Synth. Catal. 10.1002/adsc.201801015
Link to VoR: http://dx.doi.org/10.1002/adsc.201801015

10.1002/adsc.201801015
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Organocatalytic Asymmetric Domino Michael/Acyl Transfer
Reaction Between α-Nitroketones and in situ-Generated ortho-
Quinone Methides: Route to 2-(1-Arylethyl)phenols
Chandan Gharui,a Debasmita Behera,a and Subhas Chandra Pana,*
a
Department of Chemistry, Indian Institute of Technology Guwahati, Assam, India, 781039
Fax: (+91)-361-258-2349; phone: (+91)-361-258-3304; email: span@iitg.ac.in
Received:((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
Abstract: An organocatalytic asymmetric domino
Michael/acyl transfer reaction between α-nitroketones and o-
quinone methides is disclosed. o-Quinone methides are
generated in situ from 2-sulfonylmethylphenols in basic
medium. With 10 mol% of bifunctional squaramide catalyst,
high yields and excellent enantioselectivities are achieved
for a variety of O-acyl 2-(1-arylethyl)phenols under mild
reaction condition.
Keywords: o-Quinone methide; α-nitroketone; domino
reaction; 2-(1-arylethyl)phenol; asymmetric;
organocatalysis
o-Quinone methides (o-QMs) have been identified as
valuable intermediates in organic synthesis and also
in biological processes.[1] However, until the recent
years, the catalytic asymmetric versions have not
been developed mainly due to transient nature of o-
quinone methides.[2] The groups of Bach, Rueping,
Schneider, Sun, Shi, List and others have elegantly
shown chiral Brønsted acid/Lewis acid catalyzed
generation of o-QMs from o-hydroxybenzyl
alcohols/o-hydroxy styrenes/o-hydroxybenzyl ethyl
ethers.[3] Very recently also, bifunctional tertiary
amine-thiourea/squaramide catalyzed reaction of o-
QMs have been disclosed mainly using 2-
tosylmethylphenols as the substrates. For example,
Fochi, Bernardi and co-workers developed chiral
squaramide catalyzed addition of Meldrum’s acid,
malononitrile and 1,3 dicarbonyl compounds to o-
QMs which were prepared in situ from 2-
(arylsulfonyl)methyl phenols (Scheme 1).[4a]
A
related report also came from Han group.[4b] In the
same year, Zhou and co-workers reported
bifunctional organocatalyst mediated asymmetric
addition of thiols and malonitriles and recently
addition of deconjugated butenolides and azlactones
(Scheme 1).[5] Also, bifunctional squaramide
catalyzed other addition reactions to o-QMs was
recently published by Shi, Zhou and Chan (Scheme
1).[6]
Scheme 1. Representative examples of bifunctional
thiourea/squramaide catalyzed reaction with o-quinone
methides.
receptor antagonist for the treatment of urinary
incontinence and other symptoms related to an
overactive bladder.[7c] Myristinin A (B) has potent
DNA-damaging ability as well as is shown to inhibit
DNA polymerase β (IC50 2.8 μM), a DNA repair
Chiral 2-(1-phenylethyl)phenols are one of the
versatile structural motifs present in many natural
products and bioactive compounds (Figure 1).[7] For
example, (R)-tolterodine (A) is a powerful muscarine
1
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801015
Advanced Synthesis & Catalysis
enzyme.[7d] Similarly 6-benzyl-1,3- benzodioxole (F)
had shown activity against P388 murine lymphocytic
leukemia.[7g] Realizing the importance of 2-(1-
phenylethyl)phenols,[8] here in we present a direct
synthesis of 2-(1-phenylnitroethyl)-O-acyloxyphenols
via conjugate addition followed by acyl transfer
reaction between nitroketones[9] and in situ generated
o-QMs.
Table 1. Catalyst screening and optimization of reaction
conditions.
Figure 1. Selective examples of bioactive phenol
derivatives.
Entry[a] Catalyst
Solvent
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CHCl3
Yield[b]
81
ee[c]
42
74
94
96
96
96
97
98
1
2
I
We thus examined a model reaction between 2-
(phenylsulfonyl)methyl phenol 1a and nitroketone 2a
with bifunctional thiourea/squaramide catalysts and
aq. NaHCO3 (50 eq.) in dichloromethane solvent
(Table 1). After stirring at room temperature for 2.5
days with quinidine derived thiourea catalyst I (10
mol%), the desired nitroketone addition followed by
acyl transfer reaction took place and the product 3aa
was isolated in 81% yield with 42% ee (entry 1). The
enantioselectivity was improved to 74% with
bifunctional urea catalyst II (entry 2). Then we
planned to screen bifunctional squaramide
catalysts[10] and the results were encouraging for us.
For example, cinchonidine derived catalyst III having
4-trifluoromethylphenyl group provided the product
3aa in 81% yield with 94% ee (Table 1, entry 3). The
enantioselectivity was further improved by
employing quinine derived squaramide catalyst IV
having bis(trifluromethyl)phenyl group (entry 4).
Then cinchonidine and hydroquinine derived
squaramide catalysts V and VI were investigated and
identical enantioselectivities (96% ee) were attained
but slight less yield was detected with V (entries 5-6).
The enantioselectivity was slightly enhanced in
chloroform solvent with VI (entry 7). Finally, the
best result (98% ee and 93% yield) was achieved in
1,2-dichloroethane solvent and 10% aq. NaHCO3 (50
eq.) at room temperature (entry 8).. Other inorganic
bases as well as higher reaction temperature were
also tested but better result was not achieved (see
supporting information for details).
78
II
3
81
III
IV
V
4
87
5
90
6
93
VI
VI
VI
7[d]
8[d]
94
(CH2Cl)2
93
[a] Reaction condition: 0.05 mmol of 1a and 0.25 mmol of
2a in 0.6 mL solvent using 10 mol% catalyst and 10% aq.
NaHCO3 at room temperature for 2.5 days followed by
[b]
acidification using 10% aq. HCl.
Isolated yield after
silica gel column chromatography. [c] Determined by HPLC
[d]
using stationary phase chiral column.
days.
Reaction time 3
After the optimized conditions got established, the
scope and generality of the reaction was investigated.
Initially a variety of nitroketones 2 with different
electronic and steric properties was examined (Table
2). Delightfully, the reaction outcome was excellent
in almost all the cases. At the beginning, different
para-substitutions were screened and high to
excellent enantioselectivities were obtained (entries
2-9). For example, nitroketone 2b having p-tolyl
motif provided product 3ab in 92% ee. Similarly,
high enantioselectivities were achieved for products
3ac-3ae having 4- alkyl/alkoxysubstitutions (entries
3-5). Then nitroketones 2f-2h having 4-halo
2
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801015
Advanced Synthesis & Catalysis
substitutions were employed in the reaction and the
corresponding products were isolated in high yields
and with excellent enantioselectivities (entries 6-8).
In particular, product 3ah was attained in 99% yield
with 98% ee (entry 8). A biphenyl group was also
tolerated in the reaction (entry 9). Then different
meta-substitutions were studied and here also the
products were obtained in acceptable yields as well as
with high enantioselectivities (entries 10-13).
Interestingly, ortho-substitutions had no pronounced
effect on the enantioselectivitity but noticeable
influence on the yield was observed for products 3ao-
3ap (entries 15-16). A disubstituted aryl group
containing nitroketone 2q also withstood the reaction
condition and delivered product 3aq in 90% ee (entry
17). High enantioselectivity was also detected for
product 3ar
product 3as (entry 19). Moreover, an aliphatic
nitroketone 2t could also participate in the reaction
and good results were achieved.
In the next, the scope of 2-sulfonylmethylphenols
was studied and gratifyingly, a range of phenols
having variations both on the phenolic fragment and
β-aryl substituent could be employed in the reaction
and good results were achieved (Table 3). For
example, 4-methylsubstituted 2-tosylmethylphenol
1b on reaction with nitroketone 2a provided product
3ba in high yield with 94% ee. Good to high yields as
well as high enantioselectivities were maintained
with different halo substitutions on the phenol part
and the products 3ca-3ga can be further
functionalized via metal catalyzed cross-coupling
reactions (Table 3). Phenol 1h having ethoxy
substitution at 6-position was studied and provided
92% ee for product 3ha.
Table 2. Scope of nitroketones.
Table 3. Scope of 2-sulfonylmethylphenols.[a],[b]
Entry[a]
R
Yield[b] ee[c]
3
1
Ph
93
94
85
74
90
82
89
99
83
83
74
73
70
77
53
60
96
86
96
79
98
92
86
94
96
94
95
98
96
86
90
96
94
90
92
92
90
96
92
88
3aa
3ab
3ac
3ad
3ae
3af
2
4-MeC6H4
4-iPrC6H4
4-tBuC6H4
4-OMeC6H4
4-FC6H4
3
4
5
6
7
4-ClC6H4
4-BrC6H4
4-PhC6H4
3-MeC6H4
3-OMeC6H4
3-ClC6H4
3-BrC6H4
2-MeC6H4
2-OMeC6H4
2-FC6H4
3ag
3ah
3ai
8
9
10
11
12
13
14
15
16
17
18
19
20
3aj
3ak
3al
3am
3an
3ao
3ap
3aq
3ar
3as
3at
2,4-Me2C6H3
1-naphthyl
2-thienyl
nbutyl
[a]
Unless otherwise mentioned reaction was carried out
with catalyst VI in 1,2-dichloroethane at room temperature
[b]
for 3 days followed by acidification using 10% aq. HCl.
[a]
Reactions were carried out with catalyst VI in 1,2
dichloroethane at room temperature for 3 days followed by
Isolated yield after silica gel column chromatography and
enantioselectivity was determined by HPLC using
[b]
acidification using 10% aq. HCl.
Isolated yield after
[c]
stationary phase chiral column.
without HCl.
Aqueous work up
silica gel column chromatography. [c] Determined by HPLC
using stationary phase chiral column.
with naphthyl group (entry 18). Then heteroarmoatic
2-thienyl nitroketone 2s was engaged in the reaction
and gratifyingly high ee of 92% was observed for
Interestingly, in this case the higher isolated yield
(91%) was observed after doing aqueous work up
instead of aqueous hydrochloric acid due to the
3
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801015
Advanced Synthesis & Catalysis
removal of unreacted nitroketone in the aqueous
phase.
Interestingly, in this reaction concomitant reduction
to amine followed by acyl transfer reaction took place
to deliver amide 5 in 95% yield. Amide 5 was then
subjected to different protection reactions. Protection
of the phenolic OH with Boc-anhydride led to the
formation of 6 with slight reduction in enantiomeric
excess. Similarly, tosyl and methyl protections were
performed to obtain 7 and 8 respectively.
The product 3ia having sesamol motif was also
obtained in high enantioselectivity along with high
yield. Then we turned our attention to check
variations on the β-aryl group and here also different
substitutions were tolerated. Initially, different para-
substitutions were checked and excellent results were
obtained. Product 3ja having p-tolyl moiety was
isolated in 94% yield with 96% ee. Similar result was
also achieved with 4-tbutylaryl group containing 2-
sulfonylmethylphenol
1k.
Then
para-anisyl
substituted phenol 1l was employed in the reaction,
excellent yield as well as enantiomeric excess were
detected for product 3la. Electron withdrawing
functionality present at the para- position of β-aryl
part of the Phenol 1m also gave the promising result
in terms of yield and ee. Phenols having ortho- and
meta-substitutions on the β-aryl group also took part
in the reaction providing excellent results. Then
sesamol motif containing phenol 1p having β-para-
anisyl group was engaged in the reaction, this
resulted in the formation of 3pa in 88% yield with
96% ee. Then β-allyl and β-ethyl group containing
phenols 1q-1r were prepared and employed in the
reaction. To our delight, the reactions progressed well
to deliver the corresponding products in moderate
yields and enantioselectivities.
Scheme 3. Synthetic applications of 3aa.
An additional experiment was performed to
understand the mechanism of the reaction. Thus,
stabilized o-quinone methide 10[11] and nitroketone
2a were reacted under similar reaction condition and
the desired product 3pa was formed with moderate
yield and high enantioselectivity (Scheme 4). This
confirms the intermediacy of o-quinone methide in
our reaction. The absolute configuration of derivative
The reaction of 2-sulfonylmethylphenol 1a with
nitromethane as well as 1-nitropropane were also
performed in the optimized reaction conditions
however negligible conversion (<5%) was observed.
Next we examined the reaction of nitroalkanes with
stabilized o-quinone methide 10 but here also almost
no conversion was found. Thus it can be concluded
that less reactivity of nitroalkanes is responsible for
poor conversion in the reactions (Scheme 2).
6
was assigned to be (R) from X-ray
crystallography.[12] Thus it is expected that products 3
should have same absolute configuration.
Scheme 4. Reaction with preformed o-quinone methide 10.
Based on the above mechanistic evidence and the
absolute configuration, a plausible mechanism for the
formation of 3 has been shown in Scheme 5. In the
first step, base mediated desulfonylation of 1a leads
to the formation of o-quinone methide 11. Then the
bifunctional character of squaramide catalyst VI
allowed to fetch o-quinone methide 11 and
nitroketone 2a together and the desired Michael
reaction takes place from the Re face of 11 to provide
12 (Scheme 5). Hemiketalization of 12 generates
cyclic intermediate 13 which upon retro-Henry
reaction delivers product 3aa.
Scheme 2. Reactions of nitroalkanes with 1a and
preformed o-quinone methide 10.
To demonstrate the synthetic utilities of our method,
few reactions were carried out on 3aa (Scheme 3).
Initially the basic hydrolysis of 3a using sodium
hydroxide in ethanol was accomplished to provide
phenol 4 in 84% yield and the enantiopurity was
retained. Further reduction of nitro group in 4 with
zinc-acetic
acid
delivered
(R)-2-(2-amino-1-
phenylethyl)phenol 9 with high yield and excellent
enantioselectivity. Then reduction of nitro group of
product 3aa with zinc-acetic acid was carried out.
4
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801015
Advanced Synthesis & Catalysis
were prepared according to the same general
procedure where aqueous work up was performed
without using HCl to avoid the purification problem.
Acknowledgements
We thank CIF, Indian Institute of Technology Guwahati for the
instrumental facility. We also like to thank Ganesh Chandra Paul
for his help in solving crystal structure.
References
[1] For a recent review about o-QMs, see: L. Caruana, M.
Fochi, L. Bernardi, Molecules 2015, 20, 11733.
[2] For reviews, see: a) Z. Wang, J. Sun, Synthesis 2015,
47, 3629; b) A. A. Jaworski, K. A. Scheidt, J. Org.
Chem. 2016, 81, 10145.
Scheme 5. The proposed mechanism.
[3] For selected examples, see: a) D. Wilcke, E.
Herdtweck, T. Bach, Synlett 2011, 22, 1235; b) R.-Y.
Zhu, C.-S. Wang, J. Zheng, F. Shi, S.-J. Tu, J. Org.
Chem. 2014, 79, 9305; c) C.-C. Hsiao, S. Raja, H.-H.
Liao, I. Atodiresei, M. Rueping, Angew. Chem. Int. Ed.
2015, 54, 1910; d) S. Saha, C. Schneider, Org. Lett.
2015, 17, 648; e) Z. Lai, Z. Wang, J. Sun, Org. Lett.
2015, 17, 6058; f) J.-J. Zhao, S.-B. Sun, S.-H. He, Q.
Wu, F. Shi, Angew. Chem. Int. Ed. 2015, 54, 5460; g)
G. C. Tsui, L. Liu, B. List, Angew. Chem. Int. Ed.
2015, 54, 7703; h) W. Zhao, Z. Wang, B. Chu, J. Sun,
Angew. Chem. Int. Ed. 2015, 54, 1910; i) S. Saha, S. K.
Alamsetti, C. Schneider, Chem. Commun. 2015, 51,
1461; j) M. N. Grayson, J. M. Goodman, J. Org. Chem.
2015, 80, 2056; k) L. Zhang, Y. Liu, K. Liu, Z. Liu, N.
He, W. Li, Org. Biomol. Chem. 2017, 15, 8743.
In summary, we have developed a fascinating
catalytic asymmetric domino Michael/acyl transfer
reaction between o-quinone methides and α-
nitroketones. The reaction is catalyzed by easily
available hydroquinine derived squaramide catalyst.
Also, few derivatization reactions have been carried
out to show the synthetic potential of the method. The
synthesis of 2-(1-phenylethyl)phenol products in
general is difficult and thus our methodology is
important
for
the
preparation
of
2-(1-
phenylethyl)phenols in an efficient way and could be
applied in natural product synthesis.
[4] a) L. Carruna, M. Mondatori, V. Corti, S. Morales, A.
Mazzanti, M. Fochi, L. Bernardi, Chem. -Eur. J. 2015,
21, 6037; For a related report, see: b) A. Adili, Z.-L.
Tao, D.-F. Chen, Z.-Y. Han, Org. Biomol. Chem. 2015,
13, 2247.
[5] a) W. Guo, B. Wu, X. Zhou, P. Chen, X. Wang, Y.-G.
Zhou, Y. Liu, C. Li, Angew. Chem. Int. Ed. 2015, 54,
4522; b) B. Wu, X. Gao, Z. Yan, W.-X. Huang, Y.-G.
Zhou, Tetrahedron Lett. 2015, 56, 4334; c) B. Wu, X.
Gao, Z. Yan, M.-W. Chen, Y.-G. Zhou, Org. Lett.
2015, 17, 6134; d) B. Wu, Z. Yu, X. Gao, Y. Lan, Y.-
G. Zhou, Angew. Chem. Int. Ed. 2017, 56, 4006; e) J.
Zhou, M.-L. Wang, X. Gao, G.-F. Jiang, Y.-G. Zhou,
Chem. Commun. 2017, 53, 3531.
[6] a) Y. Wang, C. Zhang, H. Wang, Y. Jiang, X. Du, D.
Xu, Adv. Synth. Catal. 2017, 359, 791; b) X.-L. Jiang,
S.-J. Liu, Y.-Q. Gu, G.-J. Mei, F. Shi, Adv. Synth.
Catal. 2017, 359, 3341; c) T. Zhang, C. Ma, J.-Y.
Zhou, G.-J. Mei, F. Shi, Adv. Synth. Catal. 2018, 360,
1128; d) L. Cui, D. Lv, Y. Wang, Z. Fan, Z. Li, Z.
Zhou, J. Org. Chem. 2018, 83, 4221; e) R.-l. Liu, X.-z.
Tang, X.-J. Zhang, M. Yan, A. S. C. Chan, RSC Adv.
2017, 7, 6660.
[7] a) J. H. P. Tyman, Synthetic and Natural Phenols,
Elsevier, New York, 1996; b) J. K. Batra, L. Jurd, P. S.
Chu, C. M. Lin, E. Hamel, Mol. Pharm. 1985, 27, 94;
c) L. Nilvebrant, K.-E. Andersson, P.-G. Gillberg, M.
Stahl, B. Sparf, Eur. J. Pharmacol. 1997, 327, 195; d)
Experimental Section
General procedure for the formation of 3: To a
stirrer solution of compound 2-Sulfonylmethylphenol
1 (0.05 mmol) and α-nitroketone 2 (0.25 mmol) in
1,2-DCE solvent (0.6 mL), catalyst VI (10 mol%)
and 10% aq. NaHCO3 solution (50 eq.) were added.
Then the resulting reaction mixture was stirred at
ambient temperature for 3 days. Progress of the
reaction was then monitored by TLC analysis. After
completion of the reaction, resulting mixture was
acidified using 10% HCl solution and extracted with
DCM (2 times). Finally, organic parts were
concentrated in vacuo and subjected to the column
chromatography to obtain the desired Michael/Acyl
transfer products 3. Compounds (R)-2-ethoxy-6-(2-
nitro-1-phenylethyl)phenyl benzoate (3ha), (R)-6-(2-
nitro-1-phenylethyl)benzo[d][1,3]dioxol-5-yl
benzoate
(3ia),
(R)-2-(1-(4-methoxyphenyl)-2
nitroethyl)phenyl benzoate (3la), (R)-2-(1-(4-
fluorophenyl)-2-nitroethyl)phenyl benzoate (3ma),
(R)-2-(1-(3-methoxyphenyl)-2-nitroethyl)phenyl
benzoate (3na) and (R)-6-(1-(4-methoxyphenyl)-2
nitroethyl)benzo[d][1,3]dioxol-5-yl benzoate (3pa)
5
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801015
Advanced Synthesis & Catalysis
S. Sawadjoon, P. Kittakoop, K. Kirtikara, V. Vichai,
M. Tanticharoen, Y. Thebtaranonth, J. Org. Chem.
2002, 67, 5470; e) K. Ohmori, N. Ushimaru, K.
Suzuki, Proc. Natl. Acad. Sci. USA, 2004, 101, 12002;
f) N. Sekine, T. Ashitani, T. Murayama, S. Shibutani,
S. Hattori, K. Takahashi, J. Agric. Food Chem. 2009,
57, 5707; g) L. Jurd, V. L. Narayanan, K. D. Paull, J.
Med. Chem. 1987, 30, 1752.
[8] Y. Sohtome, B. Shin, N. Horitsugi, R. Takagi, K.
Noguchi, K. Nagasawa, Angew. Chem. Int. Ed. 2010,
49, 7299.
[9] For recent asymmetric reactions with nitroketones,
see: a) Y. Gao, Q. Ren, W.-Y. Siau, J. Wang, Chem.
Commun. 2011, 47, 5819; b) R.-J. Lu, J.-Y. Yan, J.-J.
Wang, Q.-S. Du, S.-Z. Nie, M. Yan, J. Org. Chem.
2011, 76, 6230; c) P. Li, S. H. Chan, A. S. C. Chan, F.
Y. Kwong, Org. Biomol. Chem. 2011, 9, 7997; d) R.
Maity, C. Gharui, A. K. Sil, S. C. Pan, Org. Lett. 2017,
19, 662; e) R. Maity, S. C. Pan, Org. Biomol. Chem.
2018, 16, 1598; f) K. Mondal, S. C. Pan, J. Org. Chem.
2018, 83, 5301.
[10]For reviews, see: a) J. Alemán, A. Parra, H. Jiang, K.
A. Jørgensen, Chem. Eur. J. 2011, 17, 6890; b) P.
Chauhan, S. Mahajan, U. Kaya, D. Hack, D. Enders,
Adv. Synth. Catal. 2015, 357, 25.
[11]H. Lv, W.-Q. Jia, L.-H. Sun, S. Ye, Angew. Chem. Int.
Ed. 2013, 52, 8607.
[12]CCDC 1834655 contains the crystallographic data for
compound 6.
6
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801015
Advanced Synthesis & Catalysis
COMMUNICATION
Organocatalytic Asymmetric Domino
Michael/Acyl Transfer Reaction Between α
Nitroketones and in situ-Generated ortho-Quinone
Methides: Route to 2-(1-Arylethyl)phenols
Adv. Synth. Catal. Year, Volume, Page – Page
Chandan Gharui, Debasmita Behera, Subhas
Chandra Pan*
7
This article is protected by copyright. All rights reserved.