Catalyst- and Additive-Free Decarboxylative C-4 Phosphorylation of Coumarin-3-Carboxylic Acids at Ambient Conditions

Article abstract of DOI:10.1002/adsc.202001054

A catalyst- and additive-free practical and green synthetic strategy for decarboxylative C-4 phosphorylation of coumarin-3-carboxylic acids, for the first time, has been accomplished to access a series of substituted 4-(diarylphosphoryl)chroman-2-ones at ambient conditions. The developed protocol is successfully applied to large-scale synthesis. (Figure presented.).

Full text of DOI:10.1002/adsc.202001054

Title: Catalyst- and Additive-Free Decarboxylative C-4 Phosphorylation
of Coumarin-3-Carboxylic Acids at Ambient Conditions
Authors: Goutam Brahmachari
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10.1002/adsc.202001054
Advanced Synthesis & Catalysis
Catalyst- and Additive-Free Decarboxylative C-4 Phosphorylation of
Coumarin-3-Carboxylic Acids at Ambient Conditions
Goutam Brahmacharia,*
aLaboratory of Natural Products & Organic Synthesis, Department of Chemistry, Visva-Bharati (A Central University), San-
tiniketan-731 235, West Bengal, India
E-mail: brahmg2001@yahoo.co.in; goutam.brahmachari@visva-bharati.ac.in
ORCID: http://orcid.org/0000-0001-9925-6281
Supporting information for this article is available on the WWW under https://doi.org/
ABSTRACT: A catalyst- and additive-free practical and green synthetic strategy for decarboxylative C-4 phosphorylation of cou-
marin-3-carboxylic acids, for the first time, has been accomplished to access a series of substituted 4-(diarylphosphoryl)chroman-2-
ones at ambient conditions. The developed protocol is successfully applied to large-scale synthesis.
KEYWORDS:
coumarin-3-carboxylic acids; decarboxylative C-4 phosphorylation; catalyst- and additive-free; ambient condi-
tions; gram-scale synthetic application
vealed just two earlier reports on the direct C-4 phosphoryla-
tion of coumarins to access C-4 phosphorylated chroman-2-
ones.[12] In 2012, Lenker et al.[12a] for the first-time reported the
microwave-assisted synthesis of only two such derivatives.
Later on, in 2017 Hong and co-investigators[12b] developed a
visible-light-induced photocatalytic synthetic protocol for
phosphorylated chroman-2-ones; however, their method is
non-regioselective and furnished 3,4-bis(diphenylphosphoryl)-
2H-chromen-2-ones. Scheme 1a overviews these earlier re-
ports along with their merits and demerits.
Introduction
Coumarins, an important class of O-heterocycles, are already
well-established to form the basic structural motif for a plethora
of therapeutically promising organic scaffolds of both natural
and synthetic origins, finding immense applications in treating
multifaceted disease manifestations.[1] Coumarin derivatives
are also used as additives in foods and cosmetics,[2] fragrances
and perfumes,[3] and agrochemicals,[4] Also, such molecules
find extensive applications as fluorescence sensors,[5] optical
brighteners,[6] and molecular photonic devices.[7] 3,4-Dihy-
drcoumarin, i.e. chroman-2-one is a sub-class of this group and
this interesting structural motif is also potentially found both in
natural and their synthetic analogs exhibiting a wide range of
biological profiles including antioxidant, cytotoxic, anticancer,
immunomodulatory, anti-platelet aggregation, estrogenic, anti-
bacterial and antileishmanial activity.[8] On the other hand,
phosphorus-functionalized organic molecules have also found
useful applications in the areas of industrial, agricultural, ma-
terials, and medicinal chemistry owing to their noteworthy bi-
ological and physical properties.[9] The imposition of a phos-
phoryl group on to diverse kinds of organic skeletons thus re-
mains a valid and active exercise in chemical research.[10] As
part of these research endeavors, a good deal of work on the
combination of these two units, i.e. a coumarin system and a
phosphoryl group, so as to open a route to a new class of or-
ganophosphorus compounds, has been reported in the recent
past.[10b,c, 11] However, all these literature reports basically deal
with the phosphorylation at C-3 position of a coumarin nucleus,
and were implemented under varying reaction conditions,
mostly non-ecofriendly.[11] An extensive literature survey re-
Based on this background and as part of our research en-
deavors in developing green synthetic protocols for biologi-
cally relevant compounds,[13] we targeted this interesting re-
search problem and envisioned that coumarin-3-carboxylic
acid might be a suitable substrate, which would afford the tar-
geted scaffold regioselectively via decarboxylative C-4 phos-
phorylation. To our delight, we now wish to report herein, for
the first time, a regioselective decarboxylative C-4 phosphory-
lation strategy for coumarin-3-carboxylic acids without the aid
of any catalyst or additive under ambient conditions (Scheme
1b). The key advantages of this newly developed method are
the clean reaction profile, use of no catalyst or additive, DMSO
as reaction medium, mild reaction conditions at room temper-
ature, energy-efficiency, no need of column chromatographic
purification, high atom-economy, and low E-factor, excellent
regioselectivity, good to excellent yields, and large-scale syn-
thetic applicability.
This article is protected by copyright. All rights reserved.

10.1002/adsc.202001054
Advanced Synthesis & Catalysis
2
3
4
5
6
7
8
H2O
–
–
–
–
–
–
–
rt
60
240
30
30
30
10
10
66
72
78
80
83
92
89
Scheme 1. Direct phosphorylation of coumarin-3-carbox-
ylic acids
CH2Cl2
CH3CN
1,4-dioxane
EtOH
rt
rt
rt
rt
DMSO
DMSO
rt
80 C
aReaction conditions: coumarin-3-carboxylic acid (1a; 0.1 mmol) was
stirred with diphenylphosphine oxide (2a; 0.1 mmol) in the absence or pres-
ence of solvent(s) without any additive either at room temperature (25-28
C) or heating; bIsolated yields.
Table 2
Selection of solvent
Results and Discussion
Entry
R
Solvent
DMSO
EtOH
Product Time (min)
Yield (%)a,b
To optimize the best-suited reaction conditions, we first per-
formed a series of trial reactions between coumarin-3-carbox-
ylic acid (1a; 0.1 mmol) and diphenylphosphine oxide (2a; 0.1
mmol), as our model reaction, in the absence or presence of
various solvents (viz. water, dichloromethane, acetonitrile, 1,4-
dioxane, ethanol, and dimethyl sulfoxide) in open-air either at
room or elevated temperature (Table 1, entries 1-8). Dimethyl
sulfoxide (DMSO) came out as the best solvent for this conver-
sion, just at ambient conditions, in terms of yield and time. We
thus achieved the best result for our model reaction in preparing
the desired product, 4-(diphenylphosphoryl)chroman-2-one
(3a), in 92% yield at 10 min (Table 1, entry 7) upon stirring the
reactants dissolved in 1 mL of DMSO in the open-air at room
1
2
3
4
H
3a
3a
3f
3f
10
30
15
90
92
83
71
42
H
7-OCH3
7-OCH3
DMSO
EtOH
5
6
6-NO2
6-NO2
DMSO
EtOH
3i
3i
7
76
43
60
aReaction conditions: a coumarin-3-carboxylic acid (1a/1f/1i; 0.1 mmol)
was stirred with diphenylphosphine oxide (2a; 0.1 mmol) dissolved in 1
mL of DMSO/EtOH in the absence any catalyst at room temperature (25-
28 C); bIsolated yields.

temperature (25-28 C) without any additive and/or catalyst.
To check the feasibility as well as the effectiveness of this
newly developed protocol, we then carried out a set of three
similar reactions with 6-methylcoumarin-3-carboxylic acid
(1b), 6-tert-butylcoumarin-3-carboxylic acid (1c) and 7-hy-
droxycoumarin-3-carboxylic acid (1d) using the optimized re-
action conditions; all the three reactions took place efficiently,
furnishing the expected products, viz. 4-(diphenylphosphoryl)-
Compound 3a was characterized based on detailed spectro-
scopic (1H NMR, 13C NMR, DEPT-135, 31P NMR, and HRMS)
studies. The overall results are summarized in Table 1.
It seemed that ethanol (Table 1, entry 6), yielding 83% of
3a in 30 min under identical reaction conditions, may also be a
competitive solvent for this conversion, and to explore this is-
sue, we carried out a set of two more reactions with coumarin-
3-carboxylic acids (1f/1i) substituted with electron-donating
and electron-withdrawing groups, separately in DMSO and
ethanol, using the identical reaction conditions, and compared
the results (Table 2). These experimental results, as summa-
rized in Table 2, clearly demonstrated that DMSO is the most
suitable solvent for the conversion for various substrates in
terms of reaction-times and yields of the products (3f/3i).
6-methylchroman-2-one
nylphosphoryl)chroman-2-one
(3b),
6-(tert-butyl)-4-(diphe-
(3c) and 4-(diphe-
nylphosphoryl)-7-hydroxychroman-2-one (3d), in 91%, 94%
and 96% yields, respectively, at 35, 10 and 20 min. Encouraged
with this satisfactory experimental outcomes, we then planned
to extend the substrate scope, and accordingly, another set of
seven more reactions with diversely substituted coumarin-3-
carboxylic acids (1e–1k; containing methoxy, bromo, chloro,
nitro, di-bromo and di-chloro groups) were performed under
identical reaction conditions. All these reactions underwent
smoothly, thereby affording the desired 4-(diphe-
nylphosphoryl)chroman-2-one derivatives 3e–3k with good to
excellent yields ranging from 84-96% just at 7-15 min. To our
delight, 3-oxo-3H-benzo[f]chromene-2-carboxylic acid (1l)
also took part in the reaction giving rise to the desired phos-
phorylated product, 1-(diphenylphosphoryl)-1,2-dihydro-3H-
benzo[f]chromen-3-one (3l) with 95% yield after 10 min.
Table 1. Optimization of reaction conditions
Entry
1
Solvent
(1 mL)
no solvent
Catalyst
Condition
rt
Time
(min)
60
Yield (%)a,b
We then tried to extend the scope of >P(O)H reagent and
accordingly, we carried out a set of two reactions between di-
–
–
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10.1002/adsc.202001054
Advanced Synthesis & Catalysis
p-toylphosphine oxide 2b, a variant of >P(O)H reagent, and un-
substituted coumarin-3-carboxylic acid 1a and with 6-methyl-
coumarin-3-carboxylic acid 1b, under the identical reaction
conditions. Both the reactions took place smoothly giving the
desired and known compounds, 4-(di-p-tolylphosphoryl)chro-
man-2-one (3m) and 4-(di-p-tolylphosphoryl)-6-methylchro-
man-2-one (3n), respectively, in 90% and 92% yields at 1 h;
the physical and spectral data of both the products are in close
agreement with those reported in literature.[12a] To our delight,
we were also successful in synthesizing another set of six func-
tionalized phosphorylated chroman-2-one derivatives 3o–3t
with good to excellent yields ranging from 87-94% within 1-2
h upon the reaction of the phosphorus reagent 2b with the di-
versely substituted coumarin-3-carboxylic acids (1d, 1f-h, 1j,
and 1k) under identical reaction conditions. The overall results
are shown in Table 3.
the respective E-factor and atom economy for each entry is
shown in Table 3.
Table 3. Synthesis of substituted 4-(diarylphosphoryl)-
chroman-2-ones (3)a,b
_______________________________________
However, (EtO)3P, (PhO)2P(O)H and (MeO)2P(O)H were
found not to take part in the reaction – possibly, because the P-
H hydrogen in case of the latter two reagents [(PhO)2P(O)H
and (MeO)2P(O)H] is reluctant to undergo tautomerization re-
quired for initiating decarboxylation of the coumaric acid sub-
strate. No decarboxylation occurred upon the addition of either
of the three P-reagents with coumaric acid dissolved in DMSO,
and hence, there was no reaction at all.
The synthesized compounds 3a3t were isolated pure just
upon filtration, followed by drying in the open-air; no tedious
chromatographic purification was required. All the products,
except 3m and 3n, are new and were fully characterized based
on their detailed spectral studies including 1H NMR, 13C NMR,
DEPT-135, 31P NMR, and HRMS. In support of the phosphor-
ylation taking place at C-4 of the coumarin moiety, we further
studied 2D-NMR, particularly the HMQC (1H-13C heteronu-
clear multiple quantum coherence) and HMBC (1H-13C hetero-
nuclear multiple bond correlation) spectral analysis for a repre-
sentative compound 3g (see Supporting Information) – the key
HMBC interaction between the multiplet proton signal for H-4
at H 4.64-4.60 (-CHP-) and carbon-13 signal for C-6 at C
120.48 confirmed the structure I for compound 3g, while an-
other possible structure II was discarded as no such interaction
was observed between either Ha of -CH2CO- at H 3.18-3.11(m,
merged with DMSO-d6 water peak) or Hb of -CH2CO- at H
2.57-2.52 (m) and the C-6 at C 120.48, as depicted in Figure
1.
_______________________________________
aReaction conditions: a coumarin-3-carboxylic acid (1; 0.1 mmol) was
stirred in open air with diarylphosphine oxide (2; 0.1 mmol) dissolved in 1
mL of DMSO in the absence any catalyst at room temperature (25-28 C);
bIsolated yields.
Figure 1. The key HMBC interaction in compound 3g
Herein we propose a possible mechanism for this catalyst-
and additive-free C-4 phosphorylation of substituted coumarin-
3-carboxylic acids (1) with diarylphosphine oxide (2) in
DMSO at ambient conditions, leading to the synthesis of a new
series of substituted 4-(diarylphosphoryl)chroman-2-ones (3)
(Scheme 2). Coumaric acid 1 first gets associated with the
phosphorus substrate 2 in the reaction mixture through hydro-
gen bonding between the carboxylic acidic proton and the ox-
ygen atom of Ar2P=O (2), thereby facilitating tautomeric con-
version of 2 to 2′. This less stable P(III) form 2′, which thus
generated from the P(V) form 2 via tautomerization in solution
phase (DMSO),[15] then takes part in a nucleophilic attack at C-
4 of coumarin nucleus through phosphorus (C-P -bond for-
mation)[16] to give an adduct 4 (non-isolable) that in turn affords
the desired product 3 through a rapid tautomerization, followed
To evaluate the greenness of this newly developed
method, we herein calculated (see Supporting Information) two
important green parameters,[14] i.e. E-factor (g/g), and atom
economy (AE) for all the synthesized compounds (3a–3t). The
calculated E-factors and atom economy are found to be in the
range of 0.33-0.15, and 88.78-92.39%, respectively, which are
indicative of the considerable greenness of this present method;
This article is protected by copyright. All rights reserved.

10.1002/adsc.202001054
Advanced Synthesis & Catalysis
by decarboxylation (expulsion of CO2 was detected during the
gram-scale experiment) process[17]. To validate the role of the
carboxylic acid group within the coumarin moiety, we per-
formed a set of control experiments (Scheme 2, control expe-
rient-1) with unsubstituted coumarin 5 and coumarins substi-
tuted with other groups at the 3-position (viz. 3-cyanocoumarin
6, 3-acetylcoumarin 7 and ethyl coumarin-3-carboxylate 8),
and in all these cases no reaction occurred under the optimized
conditions. These observations support our presumption that
the coumarin nucleus must bear a C3-COOH group that plays a
crucial role in initiating the reaction through hydrogen bonding.
Scheme 3. Representative gram-scale experiment (30-fold
enhancement)
____________________________________________________
Besides, the reaction media containing the residual reactants,
solvent (DMSO), and certain portions of the product obtained
upon filtration of the reaction mixture after the completion of
the reaction, followed by removal of added water (during pro-
It is thus evident from the mechanistic pathway that during
the reaction, C-3 of coumarin-3-carboxylic acids (1) becomes
saturated by adopting two hydrogen atoms, one from its -
COOH group and another from the Ar2P(O)H, not from the wa-
ter used during work-up. In support of this proposition, we per-
formed an isotope (deuterium)-labeling experiment (Scheme 2,
isotope-labeling experiment 2): deuterated coumarin-3-carbox-
ylic acid-d (1a-d1; see Supporting Information) upon reaction
with diphenylphosphine oxide-d (2a-d1)[18] furnished 4-(diphe-
nylphosphoryl)chroman-2-one-3,3-d2 (3a-d2) solely in similar
yield (91%) compared to the normal entry (Table 3, entry 1, 3a)
but with a somewhat elongated time (50 min), as usually ex-
pected for deuterated-substrates. The deuterated product 3a-d2
was characterized based on 1H-NMR and HRMS (experimental
and Supporting Information). That this C-4 phosphorylation re-
action follows an ionic path was furthermore documented by
performing radical-scavenging experiments (experiment-3 as
shown in Scheme 2) where none of the radical scavengers (viz.
TEMP, BHT, p-benzoquinone) used could inhibit the reaction
at all (see Supporting Information). The overall mechanistic as-
pects are shown in Scheme 2.

cessing) on boiling at 110 C for 1 h, was successfully reused
up to the third run in the case of a representative entry (Table
3, entry 1), viz. reaction between coumarin-3-carboxylic acid
and diphenylphosphine oxide. The desired product 3a was iso-
lated in 92, 91 and 94% yields, respectively, almost similar to
that from the first run, but the time frame was found to be elon-
gated from 10 min (1st run) to 25 min (3rd run), thereby indicat-
ing in a gradual decrease in the efficiency of the reused solvent
over further uses. The results are graphically represented in
Figure 2.
Figure 2. Reusability of reaction media (Table 3, entry 1)
Scheme 2. Proposed mechanism of decarboxylative C-4
phosphorylation of coumarin-3-carboxylic acids
Conclusions
In conclusion, we have accomplished a catalyst- and additive-
free practical and green synthetic method to access a new series
of 4-(diarylphosphoryl)chroman-2-ones via decarboxylative C-
4 phosphorylation of coumarin-3-carboxylic acids just under
ambient conditions. This is the first report on C-4 phosphory-
lation of coumarin derivatives by decarboxylation under green
conditions. The use of no catalyst or additive, green and reusa-
ble reaction media, clean reaction profile, mild reaction condi-
tions at room temperature, energy-efficiency, no column chro-
matography, thereby avoiding the use of toxic organic solvents,
excellent regioselectivity, good to excellent yields within a
short reaction time-frame, large-scale synthetic applicability,
and high atom-economy and low E-factor are the notable fea-
tures of this present protocol.
_______________________________________
We checked the effectiveness of this catalyst- and addi-
tive-free protocol for a somewhat scaled-up (on the gram scale;
3 mmol scale; 30-fold enhancement) experiment with one rep-
resentative entry (Table 3; entry 10); the large-scale reaction
afforded the target product, 6,8-dibromo-4-(diphe-
nylphosphoryl)chroman-2-one (3j), in 93% yield within 17 min
(Scheme 3). It has been revealed that the large-scale reaction is
almost similar to 0.1 mmol scale entry (Table 3, entry 10) in
terms of respective yield and time.
Experimental Section
General information. All chemicals (analytical grade) except
starting coumarin-3-carboxylic acids were purchased from re-
puted companies and used without further purification. All the
starting coumarin-3-carboxylic acids (1a-1l) used in this pre-
sent study were synthesized as per the previous report from our
laboratory.[1e] 1H-, 13C-, 31P-NMR spectra were collected at
This article is protected by copyright. All rights reserved.

10.1002/adsc.202001054
Advanced Synthesis & Catalysis

1
400, 100 and 162 MHz, respectively, on a Bruker DRX spec-
trometer using CDCl3 and DMSO-d6 as solvents. Chemical
shifts were reported in δ (ppm), relative to the internal standard,
TMS. The signals observed are described as s (singlet), d (dou-
blet), t (triplet), and m (multiplet). Coupling constants are re-
ported as J value in Hz. Mass spectrometry was obtained using
a Bruker maXis Impact (Q-TOF) high-resolution mass spec-
trometer. Elemental analyses were performed with a Perkin
Elmer 2400 Series II elemental analyzer instrument. The melt-
ing point was recorded on a Chemiline CL-725 melting point
apparatus and is uncorrected. Thin Layer Chromatography
(TLC) was performed using silica gel 60 F254 (Merck) plates.
Mp = 269 C. H NMR (400 MHz, DMSO-d6):  = 8.03-7.98
(m, 2H, Ar-H), 7.69-7.61 (m, 5H, Ar-H), 7.59-7.55 (m, 1H, Ar-
H), 7.49-7.46 (m, 2H, Ar-H), 7.03-7.01 (m, 1H, Ar-H), 6.94-
6.92 (m, 1H, Ar-H), 6.33 (br s, 1H, Ar-H), 4.54-4.50 (m, 1H, -
CHP), 2.56-2.52 (m, 1H, Hb of -CH2CO-), 1.94 (s, 3H, Ar-CH3)
ppm (signal for Ha proton of -CH2CO- is merged with DMSO-
d6 water peak). 13C NMR (100 MHz, DMSO-d6):= 166.04
(lactone CO), 150.40 (d, J3CP = 4 Hz), 132.21 (d, JCP = 2 Hz),
132.17 (dd, JCP = 26, 3 and 2 Hz), 130.74 (d, J1 = 94 Hz),
CP
131.09 (2C), 131.02 (JCP = 2 Hz, 2C), 130.95 (2C), 130.68 (d,
J1CP = 97 Hz), 129.96 (d, JCP = 4 Hz), 129.06 (d, JCP = 10 Hz,
2C), 128.31 (d, JCP = 12 Hz, 2C), 117.43 (d, JCP = 6 Hz), 116.33
(d, JCP = 2 Hz), 35.41 (d, J1CP = 64 Hz, CHP), 28.40 (CH2CO),
19.95 (Ar-CH3) ppm. 31P NMR (162 MHz, DMSO-d6): δ 32.35
ppm. HRMS: m/z 363.1150 [M + H]+ calcd for C22H19O3PH,
found: m/z 363.1150; m/z 385.0970 [M + Na]+ calcd for
C21H19O3PNa; found: m/z 385.0981.
General procedure for the synthesis of functionalized 4-(di-
arylphosphoryl)chroman-2-ones (3)
Coumarin-3-carboxylic acids (1; 0.10 mmol) and dia-
rylphosphine oxide (2; 0.10 mmol) were carefully weighed into
an oven-dried open glass-vessel equipped with a magnetic stir-
rer bar. Then dimethylsulfoxide (DMSO) (1.0 mL) was added
to the mixture, and stirred in the open-air under ambient condi-
tions for a stipulated time-frame (7 min to 2 h), with occasional
TLC monitoring to judge the progress of the reaction. On com-
pletion of the reaction, 2 mL of water was added to the resulting
mixture and shaken for a while when the product precipitated
out and allowed to settle, and then filtered off using ordinary
filter paper. Upon drying in the open-air, the desired products,
4-(diarylphosphoryl)chroman-2-ones 3 (3a–3t), were obtained
as pure. The structures of the isolated products were confirmed
by elemental analyses and detailed spectral studies including
1H-NMR, 13C-NMR, DEPT-135, 31P-NMR, and HRMS (2D-
NMR for one representative entry, 3g).
6-(tert-Butyl)-4-(diphenylphosphoryl)chroman-2-one (3c).
White amorphous solid; yield: 94% (38 mg; 0.1 mmol scale);
Mp = 272 C. 1HNMR (400 MHz, CDCl3):  = 7.92-7.87 (m,
2H, Ar-H), 7.64-7.60 (m, 1H, Ar-H), 7.58-7.51 (m, 5H, Ar-H),
7.43-7.38 (m, 2H, Ar-H), 7.25-7.22 (m, 1H, Ar-H), 6.97-6.95
(m, 1H, Ar-H), 6.49-6.48 (m, 1H, Ar-H), 3.89-3.84 (m, 1H, -
CHP), 3.22-3.15 (m, 1H, Ha of -CH2CO-), 3.07-2.93 (m, 1H,
1
Hb of -CH2CO-), 1.01 (s, 9H, (CH3)3C) ppm. H NMR (400
MHz, DMSO-d6):  = 8.56-8.01 (m, 2H, Ar-H), 7.72-7.63 (m,
5H, Ar-H), 7.56-7.52 (m, 1H, Ar-H), 7.48-7.44 (m, 2H, Ar-H),
7.24-7.20 (m, 1H, Ar-H), 6.96 (d, 1H, J = 8.4 Hz, Ar-H), 6.58-
6.57 (m, 1H, Ar-H), 4.58 (t, 1H, J = 6.8 Hz, -CHP), 2.56-2.52
(m, 1H, Hb of -CH2CO-), 0.94 (s, 9H, (CH3)3C) ppm (signal for
Ha proton of -CH2CO- is merged with DMSO-d6 water peak).
13C NMR (100 MHz, DMSO-d6):= 166.16 (lactone CO),
150.29 (d, J3CP = 4 Hz), 145.63 (d, JCP = 2 Hz), 132.14 (d, JCP
= 36 Hz), 131.16 (2C), 131.06 (JCP = 3 Hz, 2C), 130.85 (d, J1
The physical and spectroscopic data of all the compounds 3 (3a
– 3t and 3a-d2) are given below:
CP
= 91 Hz), 130.81 (d, J1CP = 98 Hz), 130.95 (2C), 129.13 (d, JCP
= 10 Hz, 2C), 128.41 (d, JCP = 12 Hz), 126.6 (d, JCP = 4 Hz),
125.61 (d, JCP = 2 Hz), 116.74 (d, JCP = 6 Hz), 116.08 (d, JCP
=
4-(Diphenylphosphoryl)chroman-2-one (3a). Bright white
amorphous solid; yield: 92% (32 mg; 0.1 mmol scale); Mp =
270 C. 1HNMR (400 MHz, CDCl3):  = 7.89-7.84 (m, 2H, Ar-
H), 7.66-7.62 (m, 1H, Ar-H), 7.60-7.54 (m, 5H, Ar-H), 7.46-
7.42 (m, 2H, Ar-H), 7.27-7.24 (m, 1H, Ar-H), 7.05-7.03 (m,
1H, Ar-H), 6.90-6.86 (m, 1H, Ar-H), 6.65-6.62 (m, 1H, Ar-H),
3.96-3.91 (m, 1H, -CHP), 3.25-3.19 (m, 1H, Ha of -CH2CO-),
3 Hz), 35.63 (d, J1 = 66 Hz, CHP), 33.76 (C(CH3)3), 30.81
CP
(C(CH3)3, 3C), 28.36 (CH2CO) ppm. 31P NMR (162 MHz,
DMSO-d6): δ 32.55 ppm. HRMS: m/z 405.1620 [M + H]+ calcd
for C25H25O3PH, found: m/z 405.1616; m/z 427.1439 [M + Na]+
calcd for C25H25O3PNa, found: m/z 427.1215; m/z 443.1178 [M
+ K]+ calcd for C25H25O3PK, found: m/z 443.1166.
1
4-(Diphenylphosphoryl)-7-hydroxychroman-2-one
(3d).
3.08-2.95 (m, 1H, Hb of -CH2CO-) ppm. HNMR (400 MHz,
White amorphous powder; yield: 96% (35 mg; 0.1 mmol
DMSO-d6):  = 8.02-7.97 (m, 2H, Ar-H), 7.75-7.69 (m, 2H,
Ar-H), 7.68-7.60 (m, 3H, Ar-H), 7.58-7.54 (m, 1H, Ar-H),
7.49-7.45 (m, 2H, Ar-H), 7.24-7.21 (m, 1H, Ar-H), 7.06-7.04
(m, 1H, Ar-H), 6.85-6.81 (m, 1H, Ar-H), 6.64-6.62 (m, 1H, Ar-
H), 4.65 (t, J = 6.8 Hz, 1H, -CHP), 2.56-2.53 (m, 1H, Hb of -
CH2CO-) ppm (signal for Ha proton of -CH2CO- is merged with
DMSO-d6 water peak). 13CNMR (100 MHz, DMSO-d6):=
1
scale); Mp = 255 C. HNMR (400 MHz, CDCl3):  = 8.65 (br
s, 1H, -OH), 7.87-7.82 (m, 2H, Ar-H), 7.67-7.61 (m, 3H, Ar-
H), 7.59-7.55 (m, 3H, Ar-H), 7.51-7.46 (m, 2H, Ar-H), 6.50 (br
s, 1H, Ar-H), 6.43-6.38 (m, 2H, Ar-H), 3.87-3.83 (m, 1H, -
CHP), 3.04-3.01 (m, 1H, Ha of -CH2CO-), 2.98-2.96 (m, 1H,
Hb of -CH2CO-) ppm. 1H NMR (400 MHz, DMSO-d6):  = 9.75
(br s, 1H, -OH), 7.99-7.94 (m, 2H, Ar-H), 7.74-7.69 (m, 2H,
Ar-H), 7.66-7.58 (m, 3H, Ar-H), 7.57-7.53 (m, 1H, Ar-H),
7.49-7.45 (m, 2H, Ar-H), 6.42-6.39 (m, 2H, Ar-H), 6.22 (dd,
1H, J = 8.4, 2.4, 2.0 Hz, Ar-H), 4.48 (t, 1H, J = 6.4 Hz, -CHP),
3.29-3.19 (m, 1H, Ha of -CH2CO-), 2.54-2.53 (m, 1H, Hb of -
CH2CO-) ppm. 13C NMR (100 MHz, DMSO-d6):= 166.09
(lactone CO, d, J3CP = 2 Hz), 157.82 (d, J5CP = 3 Hz), 153.19 (d,
166.08 (d, JCP = 4 Hz, lactone CO), 152.53 (d, J3 = 4 Hz),
CP
132.28 (d, JCP = 15 Hz), 131.07 (2C), 130.99 (2C), 130.96 (d,
J1CP = 93 Hz), 130.92, 130.65 (d, J1CP = 97 Hz), 129.50 (d, JCP
= 4 Hz), 129.15 (d, JCP = 12 Hz, 2C), 128.90, 128.54 (d, JCP
12 Hz, 2C), 123.49, 117.99 (d, JCP = 6 Hz), 116.82, 35.25 (J1
=
CP
= 65 Hz, CHP), 28.43 (CH2CO) ppm. 31P NMR (162 MHz,
CDCl3): δ 32.21 ppm. HRMS: m/z 349.0994 [M + H]+ calcd for
C21H17O3PH, found: m/z 349.0988; m/z 387.0552 [M + K]+
calcd for C21H17O3PK, found: m/z 387.0548.
J3 = 4 Hz ), 132.08 (d, JCP = 15 Hz), 131.27 (d, J1CP = 85 Hz
CP
), 131.04 (2C), 130.94 (2C), 130.93 (d, J1CP = 97 Hz ), 130.84
(2C), 129.98 (d, JCP = 4 Hz, 2C), 129.02 (d, JCP = 11 Hz ),
128.43 (d, JCP = 12 Hz ), 110.82 (d, JCP = 3 Hz ), 107.56 (d, JCP
4-(Diphenylphosphoryl)-6-methylchroman-2-one
(3b).
White amorphous solid; yield: 91% (33 mg; 0.1 mmol scale);
This article is protected by copyright. All rights reserved.

10.1002/adsc.202001054
Advanced Synthesis & Catalysis
= 6 Hz ), 103.56, 34.48 (d, J1CP = 66 Hz, CHP), 28.68 (CH2CO)
ppm. 31P NMR (162 MHz, DMSO-d6): δ 32.01 ppm. HRMS:
m/z 365.0943 [M + H]+ calcd for C21H17O4PH, found: m/z
365.0941; m/z 387.0762 [M + Na]+ calcd for C21H17O4PNa,
found: m/z 387.0766.
H), 7.04 (d, 1H, J = 8.8 Hz, Ar-H), 6.72-6.71 (m, 1H, Ar-H),
4.64-4.60 (m, 1H, -CHP), 2.57-2.52 (m, 1H, Hb of -CH2CO-)
ppm (signal for Ha proton of -CH2CO- is merged with DMSO-
d6 water peak). 13C NMR (100 MHz, DMSO-d6):= 165.40
(lactone CO), 151.72 (d, J3CP = 7 Hz), 132.48, 132.16 (dd, JCP
= 26, 4 and 2 Hz), 131.39 (d, JCP = 2 Hz), 131.02 (2C), 130.94
(2C), 130.23 (d, JCP = 94 Hz), 130.17 (d, JCP = 97 Hz), 129.16
(d, JCP = 11 Hz, 2C), 128.47 (d, JCP = 12 Hz, 2C), 120.48 (d,
JCP = 6 Hz), 118.79 (d, JCP = 3 Hz, 2C), 114.88 (d, JCP = 2 Hz),
35.39 (d, J1CP = 65 Hz, CHP), 27.94 (CH2CO) ppm. 2D-NMR:
Selected HMQC interactions at  3.18-3.11 (m, Ha of -CH2CO-
, merged with DMSO-d6 water peak) vs 27.94 (CH2CO), 
2.57-2.52 (m, Hb of -CH2CO-) vs 27.94 (CH2CO),  4.64-4.60
(-CHP-) vs 35.39 (CHP); HMBC interaction (selected) at 
4.64-4.60 (-CHP-) vs 120.48 (C-6). 31P NMR (162 MHz,
DMSO-d6): δ 32.63 ppm. HRMS: m/z 427.0099 [M + H]+ calcd
for C21H16BrO3PH; found: m/z 427.0097; m/z 448.9918 [M +
Na]+ calcd for C21H16BrO3PNa; found: m/z 448.9882.
4-(Diphenylphosphoryl)-6-methoxychroman-2-one
(3e).
White amorphous solid; yield: 93% (35 mg; 0.1 mmol scale);
1
Mp = 281 C. HNMR (400 MHz, CDCl3):  = 7.86-7.81 (m,
2H, Ar-H), 7.63-7.51 (m, 6H, Ar-H), 7.45-7.40 (m, 2H, Ar-H),
6.56-6.55 (m, 1H, Ar-H), 6.51-6.48 (m, 1H, Ar-H), 6.43-6.40
(m, 1H, Ar-H), 3.88-3.79 (m, 1H, -CHP), 3.76 (s, 3H, Ar-
OCH3), 3.20-3.13 (m, 1H, Ha of -CH2CO-), 3.03-2.89 (m, 1H,
1
Hb of -CH2CO-) ppm. H NMR (400 MHz, DMSO-d6):  =
8.03-7.98 (m, 2H, Ar-H), 7.75-7.70 (m, 2H, Ar-H), 7.67-7.61
(m, 3H, Ar-H), 7.59-7.55 (m, 1H, Ar-H), 7.51-7.47 (m, 2H, Ar-
H), 6.99-6.97 (m, 1H, Ar-H), 6.79-6.76 (m, 1H, Ar-H), 6.14-
6.13 (m, 1H, Ar-H), 4.59-4.55 (m, 1H, -CHP), 3.36 (s, 3H, Ar-
OCH3), 2.55-2.53 (m, 1H, Hb of -CH2CO-) ppm (signal for Ha
proton of -CH2CO- is merged with DMSO-d6 water peak). 13
C
6-Chloro-4-(diphenylphosphoryl)chroman-2-one
(3h).
NMR (100 MHz, DMSO-d6):= 166.06 (d, J3 = 3 Hz, lac-
CP
White amorphous solid; yield: 94% (36 mg; 0.1 mmol scale);
Mp = 283 C. 1HNMR (400 MHz, CDCl3):  = 7.89-7.84 (m,
2H, Ar-H), 7.66-7.63 (m, 1H, Ar-H), 7.59-7.54 (m, 5H, Ar-H),
7.48-7.42 (m, 2H, Ar-H), 7.21-7.18 (m, 1H, Ar-H), 6.98-6.96
(m, 1H, Ar-H), 6.49-6.48 (m, 1H, Ar-H), 3.85-3.80 (m, 1H, -
CHP), 3.18-3.11 (m, 1H, Ha of -CH2CO-), 3.04-2.90 (m, 1H,
Hb of -CH2CO-) ppm. 1H NMR (400 MHz, DMSO-d6):  =
8.02-7.97 (m, 2H, Ar-H), 7.69-7.59 (m, 6H, Ar-H), 7.49 (br s,
2H, Ar-H), 7.29-7.27 (m, 1H, Ar-H), 7.10-7.08 (m, 1H, Ar-H),
6.59 (br s, 1H, Ar-H), 4.64-4.61 (m, 1H, -CHP), 2.57-2.54 (m,
1H, Hb of -CH2CO-) ppm (signal for Ha proton of -CH2CO- is
merged with DMSO-d6 water peak). 13C NMR (100 MHz,
DMSO-d6): = 165.45 (lactone CO), 155.65, 132.67, 132.48,
132.31, 131.19 (JCP = 8 Hz), 131.02 (2C), 130.94 (2C), 130.69
(JCP = 8 Hz), 129.22 (2C), 129.09 (JCP = 5 Hz, 2C), 128.51 (JCP
tone CO), 159.58, 154.64 (d, J3 = 3 Hz), 132.31 (d, JCP = 2
CP
Hz), 132.08 (d, JCP = 2 Hz), 131.09 (d, JCP = 9 Hz, 2C), 130.94
(d, JCP = 9 Hz, 2C), 130.82 (d, J1CP = 93 Hz), 130.72 (d, J1
=
CP
97 Hz), 129.09 (JCP = 10 Hz, 2C), 128.46 (JCP = 11 Hz, 2C),
118.58 (JCP = 6 Hz), 117.45, 114.73, 113.85 (JCP = 5 Hz), 55.09
(Ar-OCH3), 35.59 (d, J1 = 65 Hz, CHP), 28.21 (CH2) ppm.
CP
31P NMR (162 MHz, DMSO-d6): δ 32.20 ppm. HRMS: m/z
378.1021 [M]+ calcd for C22H19O4P, found: m/z 378.0150.
4-(Diphenylphosphoryl)-7-methoxychroman-2-one
(3f).
White amorphous solid; yield: 85% (32 mg; 0.1 mmol scale);
Mp = 251 C. 1HNMR (400 MHz, CDCl3):  = 7.88-7.83 (m,
2H, Ar-H), 7.64-7.53 (m, 6H, Ar-H), 7.46-7.41 (m, 2H, Ar-H),
6.94-6.92 (m, 1H, Ar-H), 6.79-6.75 (m, 1H, Ar-H), 6.06-6.05
(m, 1H, Ar-H), 3.89-3.84 (m, 1H, -CHP), 3.45 (s, 3H, Ar-
OCH3), 3.23-3.16 (m, 1H, Ha of -CH2CO-), 3.04-2.89 (m, 1H,
= 10 Hz, 2C), 118.44, 102.03 (JCP = 54 Hz ), 35.42 (d, J1
=
CP
1
Hb of -CH2CO-) ppm. H NMR (400 MHz, DMSO-d6):  =
64 Hz, CHP), 27.94 (CH2CO) ppm. 31P NMR (162 MHz,
DMSO-d6): δ 32.56 ppm. HRMS: m/z 383.0604 [M + H]+ calcd
for C21H16ClO3PH, found: m/z 383.0617; m/z 405.0423 [M +
Na]+ calcd for C21H16ClO3PNa; found: m/z 405.0437; m/z
421.0163 [M + K]+ calcd for C21H16ClO3PNK; found: m/z
421.0175.
8.00-7.95 (m, 2H, Ar-H), 7.76-7.71 (m, 2H, Ar-H), 7.65-7.59
(m, 3H, Ar-H), 7.55-7.53 (m, 1H, Ar-H), 7.49-7.45 (m, 2H, Ar-
H), 6.66 (d, 1H, J = 2.4 Hz, Ar-H), 6.54-6.52 (m, 1H, Ar-H),
6.44-6.41 (m, 1H, Ar-H), 4.58-4.54 (m, 1H, -CHP), 3.69 (s, 3H,
Ar-OCH3), 3.33-3.23 (m, 1H, Ha of -CH2CO-), 2.55-2.52 (m,
1H, Hb of -CH2CO-) ppm. 13C NMR (100 MHz, DMSO-
d6):= 165.97 (lactone CO, d, JCP = 3 Hz), 159.60 (d, J5CP = 2
4-(Diphenylphosphoryl)-6-nitrochroman-2-one (3i). Pale
yellow amorphous solid; yield: 84% (33 mg; 0.1 mmol scale);
Hz), 153.36 (d, J3 = 5 Hz), 132.14 (dd, JCP = 11 and 2 Hz),
1

CP
Mp = 288 C. H NMR (400 MHz, DMSO-d6): δ = 8.12-8.09
(m, 1H, Ar-H), 8.06-8.01 (m, 2H, Ar-H), 7.71-7.65 (m, 4H, Ar-
H), 7.57-7.53 (m, 2H, Ar-H), 7.48-7.45 (m, 3H, Ar-H), 7.33-
7.31 (m, 1H, Ar-H), 4.85-4.81 (m, 1H, -CHP), 2.64-2.58 (m,
1H, Hb of -CH2CO-) ppm (signal for Ha proton of -CH2CO- is
merged with DMSO-d6 water peak). 13C NMR (100 MHz,
131.14 (d, J1 = 92 Hz), 131.02, 130.92 (2C), 130.82 (2C),
CP
130.82 (d, J1CP = 97 Hz), 129.97 (d, JCP = 3 Hz), 129.04 (d, JCP
= 10 Hz, 2C), 128.48 (d, JCP = 11 Hz, 2C), 109.74 (d, JCP = 3
Hz), 109.40 (d, JCP = 6 Hz), 102.25, 55.43 (Ar-OCH3), 34.49
(d, J1 = 66 Hz, CHP), 28.57 (d, J2 = 2 Hz, CH2CO) ppm.
CP
CP
31P NMR (162 MHz, DMSO-d6): δ 32.05 ppm. HRMS: m/z
401.0919 [M + Na]+ calcd for C22H19O4PNa; Found: m/z
401.0927.
DMSO-d6): δ = 164.76 (lactone CO), 157.12, 142.53 (d, JCP
=
19 Hz), 132.53 (d, JCP = 23 Hz), 131.08, 130.98 (2C), 130.88,
129.76 (d, J1CP = 104 Hz), 129.23 (JCP = 11 Hz, 2C), 129.73 (d,
JCP = 97 Hz), 128.91, 128.53 (JCP = 12 Hz, 2C), 125.16 (d, JCP
= 5 Hz), 124.54, 119.61 (d, JCP = 6 Hz), 117.93 (JCP = 1 Hz),
35.52 (d, J1CP = 64 Hz, CHP), 27.62 (CH2CO) ppm. 31P NMR
(162 MHz, DMSO-d6): δ 33.10 ppm. HRMS: m/z 416.0664 [M
+ Na]+ calcd for C21H16NO5PNa; found: m/z 416.0759.
6-Bromo-4-(diphenylphosphoryl)chroman-2-one
(3g).
White amorphous solid; yield: 94% (40 mg; 0.1 mmol scale);
Mp = 289 C. 1HNMR (400 MHz, CDCl3):  = 7.89-7.85 (m,
2H, Ar-H), 7.67-7.63 (m, 1H, Ar-H), 7.60-7.53 (m, 5H, Ar-H),
7.48-7.43 (m, 2H, Ar-H), 7.36-7.33 (m, 1H, Ar-H), 6.93-6.91
(m, 1H, Ar-H), 6.61-6.60 (m, 1H, Ar-H), 3.83-3.78 (m, 1H, -
CHP), 3.18-3.11 (m, 1H, Ha of -CH2CO-), 3.04-2.90 (m, 1H,
6,8-Dibromo-4-(diphenylphosphoryl)chroman-2-one (3j).
White amorphous solid; yield: 95% (48 mg; 0.1 mmol scale);
Mp = 239-341 C. 1HNMR (400 MHz, CDCl3):  = 7.89-7.83
(m, 2H, Ar-H), 7.68-7.64 (m, 1H, Ar-H), 7.62-7.58 (m, 4H, Ar-
H), 7.56-7.53 (m, 2H, Ar-H), 7.49-7.47 (m, 2H, Ar-H), 6.55-
1
Hb of -CH2CO-) ppm. H NMR (400 MHz, DMSO-d6):  =
8.02-7.97 (m, 2H, Ar-H), 7.71-7.63 (m, 5H, Ar-H), 7.61-7.57
(m, 1H, Ar-H), 7.52-7.48 (m, 2H, Ar-H), 7.41-7.38 (m, 1H, Ar-
This article is protected by copyright. All rights reserved.

10.1002/adsc.202001054
Advanced Synthesis & Catalysis
6.54 (m, 1H, Ar-H), 3.84-3.79 (m, 1H, -CHP), 3.17-3.11 (m,
1H, Ha of -CH2CO-), 3.04-2.90 (m, 1H, Hb of -CH2CO-) ppm.
1H NMR (400 MHz, DMSO-d6): δ = 8.03-7.97 (m, 2H, Ar-H),
7.78-7.77 (m, 1H, Ar-H), 7.70-7.66 (m, 5H, Ar-H), 7.59-7.58
(m, 1H, Ar-H), 7.53-7.48 (m, 2H, Ar-H), 6.71-6.70 (m, 1H, Ar-
2H, Ar-H), 7.43-7.38 (m, 2H, Ar-H), 7.33-7.31 (m, 2H, Ar-H),
7.23-7.19 (m, 3H, Ar-H), 7.00-6.98 (m, 1H, Ar-H), 6.89-6.86
(m, 1H, Ar-H), 6.85-6.65 (m, 1H, Ar-H), 3.91-3.85 (m, 1H, -
CHP), 3.24-3.17 (m, 1H, Ha of -CH2CO-), 3.02-2.89 (m, 1H,
Hb of -CH2CO-), 2.42 (s, 3H, Ar-CH3), 2.38 (s, 3H, Ar-CH3)
ppm. 13CNMR (100 MHz, DMSO-d6):= 166.06 (d, J3CP = 3
Hz, lactone CO), 152.45 (d, J3CP = 5 Hz), 142.27, 142.03 (d, JCP
H), 4.69-4.66 (m, 1H, -CHP), 2.57-2.53 (m, 1H, Hb of
-
CH2CO-) ppm (signal for Ha proton of -CH2CO- is merged with
DMSO-d6 water peak). 13CNMR (100 MHz, DMSO-d6): δ =
164.69 (d, J3 = 3 Hz, lactone CO), 148.75 (d, J3 = 4 Hz),
= 3 Hz), 130.98 (d, JCP = 10 Hz), 130.93 (2C), 130.88 (d, JCP
=
10 Hz), 129.62 (d, JCP = 11 Hz, 2C), 129.50 (d, JCP = 4 Hz),
129.03 (d, JCP = 12 Hz, 2C), 128.71 (d, JCP = 2 Hz), 127.94 (d,
JCP = 96 Hz), 127.60 (d, JCP = 100 Hz), 123.44, 118.22 (JCP = 6
CP
CP
133.89 (d, JCP = 3 Hz), 132.58, 132.40 (d, JCP = 2 Hz), 131.55
(d, JCP = 5 Hz), 131.03 (d, JCP = 3 Hz, 2C), 130.93 (2C), 129.88
(d, J1CP = 93 Hz), 129.82 (d, J1CP = 98 Hz), 129.20 (d, JCP = 12
Hz, 2C), 128.52 (d, JCP = 12 Hz, 2C), 122.09 (d, JCP = 5 Hz),
Hz), 116.72 (JCP = 3 Hz), 35.34 (J1 = 65 Hz, CHP), 28.43
CP
(CH2CO), 21.08 (Ar-CH3, 2C) ppm. 31P NMR (162 MHz,
DMSO-d6): δ 32.50 ppm. Elemental analysis: calcd (%) for
C23H21O3P: C, 73.40; H, 5.62; Found: C, 73.48; H, 5.69.
114.95 (d, JCP = 4 Hz), 110.85 (d, J3CP = 3 Hz), 35.90 (d, J1
=
CP
64 Hz, CHP), 27.79 (d, J3CP = 2 Hz, CH2CO) ppm. 31P NMR
(162 MHz, DMSO-d6): δ 32.98 ppm. HRMS: m/z 526.9023 [M
+ Na]+ calcd for C21H15Br2O3PNa, found: m/z 526.9013 [M +
Na]+, 528.8996 [M + 2 + Na]+ and 530.8978 [M + 4 + Na]+.
4-(di-p-tolylphosphoryl)-6-methylchroman-2-one (3n).[12a]
White amorphous solid; yield: 92% (36 mg; 0.1 mmol scale);
Mp = 274-276 C. 1H NMR (400 MHz, CDCl3):  = 7.71-7.66
(m, 2H, Ar-H), 7.42-7.37 (m, 2H, Ar-H), 7.33-7.31 (m, 2H, Ar-
H), 7.22-7.19 (m, 2H, Ar-H), 7.02-7.00 (m, 1H, Ar-H), 6.88-
6.86 (m, 1H, Ar-H), 6.37 (br s, 1H, Ar-H), 3.82-3.77 (m, 1H, -
CHP), 3.20-3.14 (m, 1H, Ha of -CH2CO-), 3.00-2.87 (m, 1H,
Hb of -CH2CO-), 2.42 (s, 3H, Ar-CH3), 2.83 (s, 3H, Ar-CH3),
2.07 (s, 3H, Ar-CH3) ppm. 13C NMR (100 MHz, CDCl3):=
166.05 (d, J3 = 3 Hz, lactone CO), 150.49 (d, J3 = 5 Hz),
6,8-Dichloro-4-(diphenylphosphoryl)chroman-2-one (3k).
White amorphous solid; yield: 96% (40 mg; 0.1 mmol scale);
1

Mp = 274 C. HNMR (400 MHz, CDCl3):  = 7.89-7.84 (m,
2H, Ar-H), 7.68-7.64 (m, 1H, Ar-H), 7.62-7.55 (m, 5H, Ar-H),
7.49-7.45 (m, 2H, Ar-H), 7.32-7.31 (m, 1H, Ar-H), 6.39-6.38
(m, 1H, Ar-H), 3.86-3.81 (m, 1H, -CHP), 3.18-3.11 (m, 1H, Ha
of -CH2CO-), 3.04-2.91 (m, 1H, Hb of -CH2CO-) ppm. 1H NMR
(400 MHz, DMSO-d6): δ = 8.02-7.98 (m, 2H, Ar-H), 7.72-7.65
(m, 5H, Ar-H), 7.59-7.57 (m, 2H, Ar-H), 7.53-7.48 (m, 2H, Ar-
H), 6.57-6.56 (m, 1H, Ar-H), 4.70 (t, 1H, J = 6.8 Hz, -CHP),
2.59-2.54 (m, 1H, Hb of -CH2CO-) ppm (signal for Ha proton
of -CH2CO- is merged with DMSO-d6 water peak). 13C NMR
CP
CP
143.21 (d, JCP = 3 Hz, 2C), 133.49 (d, JCP = 3 Hz), 131.94 (d,
JCP = 9 Hz, 2C), 131.71 (JCP = 8 Hz, 2C), 130.14 (d, JCP = 4
Hz), 129.83, 129.72 (d, JCP = 12 Hz, 2C), 129.27 (d, JCP = 12
Hz, 2C), 126.45 (d, J1 = 99 Hz), 125.58 (d, J1 = 100 Hz),
CP
CP
117.23 (d, JCP = 2 Hz), 116.95 (d, JCP = 4 Hz), 38.08 (d, J1
=
CP
(100 MHz, DMSO-d6): δ = 164.56 (lactone CO), 147.30 (d, J3
CP
65 Hz, CHP), 28.93 (CH2CO), 21.76 (2C, Ar-CH3), 20.64 (Ar-
CH3) ppm. 31P NMR (162 MHz, CDCl3): δ 31.75 ppm. Ele-
mental analysis: calcd (%) for C24H23O3P: C, 73.83; H, 5.94;
Found: C, 73.91; H, 5.98.
= 4 Hz ), 132.49 (d, JCP = 17 Hz), 131.01 (2C), 130.93 (2C),
129.88 (d, J1 = 94 Hz), 129.83 (d, J1 = 98 Hz), 129.52,
CP
CP
129.20 (d, JCP = 12 Hz, 2C), 128.54 (d, JCP = 12 Hz, 2C), 128.56
(d, JCP = 3 Hz), 128.00 (d, JCP = 4 Hz), 126.97 (d, JCP = 2 Hz),
121.84 (d, JCP = 5 Hz), 121.38, 35.91 (d, J1CP = 63 Hz, CHP),
27.70 (CH2CO) ppm. 31P NMR (162 MHz, DMSO-d6): δ 32.76
ppm. HRMS: m/z 417.0214 [M + H]+ calcd for C21H15Cl2O3PH,
found: m/z 417.0219; m/z 439.0034 [M + Na]+ calcd for
C21H15Cl2O3PNa; found: m/z 439.0046.
4-(Di-p-tolylphosphoryl)-7-hydroxychroman-2-one
(3o).
White amorphous powder; yield: 87% (34 mg; 0.1 mmol

scale); Mp = 278-279 C. 1HNMR (400 MHz, CDCl3):  =
7.72-7.67 (m, 2H, Ar-H), 7.52-7.48 (m, 2H, Ar-H), 7.36-7.34
(m, 2H, Ar-H), 7.29-7.27 (m, 2H, Ar-H), 6.49-6.48 (m, 1H, Ar-
H), 6.46-6.39 (m, 2H, Ar-H), 3.81-3.77 (m, 1H, -CHP), 3.01-
2.99 (m, 1H, Ha of -CH2CO-), 2.95-2.93 (m, 1H, Hb of -
CH2CO-), 2.43 (s, 3H, Ar-CH3), 2.41 (s, 3H, Ar-CH3) ppm. 13C
1-(Diphenylphosphoryl)-1H-benzo[f]chromen-3(2H)-one
(3l). White amorphous solid; yield: 95% (38 mg; 0.1 mmol
scale); Mp = 270 C. 1H NMR (400 MHz, DMSO-d6): δ = 8.19-
8.15 (m, 2H, Ar-H), 7.89 (d, 1H, J = 8.8 Hz, Ar-H), 7.78-7.68
(m, 4H, Ar-H), 7.48 (d, 1H, J = 8.4 Hz, Ar-H), 7.32 (d, 1H, J =
8.8 Hz, Ar-H), 7.27-7.18 (m, 4H, Ar-H), 7.09-7.05 (m, 2H, Ar-
H), 7.03-6.99 (m, 1H, Ar-H), 5.10-5.08 (m, 1H, -CHP), 2.73-
2.67 (m,1H, Hb of -CH2CO-) ppm (signal for Ha proton of -
CH2CO- is merged with DMSO-d6 water peak). 13C NMR (100
MHz, DMSO-d6): δ = 166.19 (J3CP = 2 Hz, lactone CO), 150.70
NMR (100 MHz, DMSO-d6):= 166.27 (lactone CO, d, J3
CP
= 3 Hz), 157.77, 153.19 (d, J3CP = 4 Hz), 142.20 (d, JCP = 2 Hz),
141.97 (d, JCP = 4 Hz), 131.05 (d, JCP = 10 Hz, 2C), 130.90 (d,
JCP = 8 Hz, 2C), 130.10 (d, JCP = 2 Hz), 129.64 (d, JCP = 11 Hz,
2C), 129.07 (d, JCP = 12 Hz, 2C), 128.26 (d, J1 = 93 Hz),
CP
127.90 (d, J1CP = 98 Hz), 110.89, 107.83, 103.57, 34.56 (d, J1
CP
= 64 Hz, CHP), 28.73 (CH2CO), 21.15 (2C, Ar-CH3) ppm. 31
P
NMR (162 MHz, DMSO-d6): δ 29.19 ppm. Elemental analysis:
calcd (%) for C23H21O4P: C, 70.40; H, 5.39; Found: C, 70.51;
H, 5.42.
(J3CP = 6 Hz), 132.55, 131.83, 131.58 (J3CP = 9 Hz), 130.99 (J3
CP
= 9 Hz), 130.78 (J3CP = 97 Hz), 130.76 (J3CP = 101 Hz), 130.69
(J3CP = 3 Hz), 129.95, 129.80 (JCP = 2 Hz), 129.14 (JCP = 11 Hz,
2C), 127.94 (2C), 127.83 (2C), 125.84, 124.41, 123.86, 122.14,
117.32 (JCP = 2 Hz), 111.57 (JCP = 7 Hz), 32.76 (J1CP = 64 Hz,
CHP), 29.26 (CH2CO) ppm. 31P NMR (162 MHz, DMSO-d6):
δ 32.66 ppm. HRMS: m/z 399.1150 [M + H]+ calcd for
C25H19O3PH, found: m/z 399.1142; m/z 421.0970 [M + Na]+
calcd for C25H19O3PNa; found: m/z 421.1083.
4-(Di-p-tolylphosphoryl)-7-methoxychroman-2-one (3p).
White amorphous solid; yield: 91% (37 mg; 0.1 mmol scale);
Mp = 237-238 C. 1HNMR (400 MHz, CDCl3):  = 7.70-7.65
(m, 2H, Ar-H), 7.45-7.40 (m, 2H, Ar-H), 7.33-7.30 (m, 2H, Ar-
H), 7.23-7.20 (m, 2H, Ar-H), 6.55-6.53 (m, 2H, Ar-H), 6.45-
6.42 (m, 1H, Ar-H), 3.85-3.79 (m, 1H, -CHP), 3.76 (s, 3H, Ar-
OCH3), 3.21-3.14 (m, 1H, Ha of -CH2CO-), 3.00-2.86 (m, 1H,
Hb of -CH2CO-), 2.42 (s, 3H, Ar-CH3), 2.39 (s, 3H, Ar-CH3)
ppm. 13CNMR (100 MHz, CDCl3):= 165.81 (d, J3CP = 2 Hz,
lactone CO), 160.39 (d, J5CP = 3 Hz), 153.48 (d, J3CP = 4 Hz),
4-(Di-p-tolylphosphoryl)chroman-2-one (3m).[12a] White
amorphous powder; yield: 90% (34 mg; 0.1 mmol scale); Mp
= 265-268 C. 1HNMR (400 MHz, CDCl3):  = 7.71-7.66 (m,
This article is protected by copyright. All rights reserved.

10.1002/adsc.202001054
Advanced Synthesis & Catalysis
143.18, 131.91 (d, J2CP = 9 Hz, 2C), 131.62 (d, J2CP = 9 Hz, 2C),
130.40 (d, JCP = 4 Hz, 2C), 129.77 (d, JCP = 12 Hz, 2C), 129.39
6,8-Dichloro-4-(di-p-tolylphosphoryl)chroman-2-one (3t).
White amorphous solid; yield: 94% (42 mg; 0.1 mmol scale);
Mp = 281-282 C. 1HNMR (400 MHz, CDCl3):  = 7.73-7.69
(m, 2H, Ar-H), 7.45-7.40 (m, 2H, Ar-H), 7.37-7.35 (m, 3H, Ar-
H), 7.30-7.29 (m, 1H, Ar-H), 7.25-7.24 (m, 1H, Ar-H), 6.41-
6.40 (m, 1H, Ar-H), 3.83-3.78 (m, 1H, -CHP), 3.18-3.11 (m,
1H, Ha of -CH2CO-), 3.01-2.88 (m, 1H, Hb of -CH2CO-), 2.44
(s, 3H, Ar-CH3), 2.41 (s, 3H, Ar-CH3) ppm. 13C NMR (100
MHz, CDCl3):= 163.94 (d, JCP = 3 Hz, lactone CO), 143.78
(d, J3CP = 2 Hz, 2C), 131.71 (d, JCP = 9 Hz, 2C), 131.62 (d, JCP
= 9 Hz, 2C), 130.33 (d, JCP = 2 Hz), 130.04 (d, JCP = 12 Hz,
2C), 129.70, 129.60 (d, JCP = 12 Hz, 2C), 128.70 (d, JCP = 4
(d, JCP = 13 Hz, 2C), 126.65 (d, J1CP = 116 Hz), 125.66 (d, J1
CP
= 117 Hz), 110.58 (d, JCP = 3 Hz), 108.99 (d, JCP = 4 Hz),
102.75 (d, JCP = 2 Hz), 55.62 (Ar-OCH3), 37.16 (d, J1 = 67
CP
Hz, CHP), 29.01 (CH2CO), 21.79 (Ar-CH3, 2C) ppm. 31P NMR
(162 MHz, CDCl3): δ 31.66 ppm. Elemental analysis: calcd (%)
for C24H23O4P: C, 70.93; H, 5.70; Found: C, 70.99; H, 5.78.
6-Bromo-4-(di-p-tolylphosphoryl)chroman-2-one
(3q).
White amorphous solid; yield: 92% (42 mg; 0.1 mmol scale);
Mp = 285-286 C. 1HNMR (400 MHz, CDCl3):  = 7.75-7.69
(m, 2H, Ar-H), 7.42-7.30 (m, 5H, Ar-H), 7.24-7.22 (m, 2H, Ar-
H), 6.88 (d, 1H, J = 8.8 Hz, Ar-H), 6.59 (br s, 1H, Ar-H), 3.80-
3.76 (m, 1H, -CHP), 3.16-3.09 (m, 1H, Ha of -CH2CO-), 3.01-
2.87 (m, 1H, Hb of -CH2CO-), 2.44 (s, 3H, Ar-CH3), 2.39 (s,
3H, Ar-CH3) ppm. 13C NMR (100 MHz, CDCl3):= 165.08
Hz), 127.77 (d, JCP = 3 Hz), 125.61 (d, J1 = 98 Hz), 125.13
CP
(d, J1 = 102 Hz), 123.41 (d, JCP = 4 Hz), 120.79 (d, JCP = 4
CP
Hz), 38.58 (d, J1CP = 64 Hz, CHP), 28.53 (CH2CO), 21.80 (2C,
Ar-CH3) ppm. 31P NMR (162 MHz, CDCl3): δ 31.92 ppm. El-
emental analysis: calcd (%) for C23H19Cl2O3P: C, 62.04; H,
4.30; Found: C, 62.11; H, 4.32.
(lactone CO), 151.74 (d, J3CP = 5 Hz), 143.59, 132.34 (d, JCP
=
3 Hz), 132.13 (d, JCP = 2 Hz), 131.72 (d, JCP = 8 Hz, 2C), 131.64
(d, JCP = 8 Hz, 2C), 129.96 (d, JCP = 12 Hz, 2C), 129.49 (d, JCP
4-(Diphenylphosphoryl)chroman-2-one-3,3-d2
(3a-d2).
= 13 Hz, 2C), 125.89 (d, J1 = 99 Hz), 125.39 (d, J1CP = 102
CP
White amorphous solid; yield: 89% (31 mg; 0.1 mmol scale);
1
Hz), 119.66 (d, JCP =5 Hz), 119.21 (2C), 116.32, (d, JCP =5
Hz), 38.15 (d, J1CP = 64 Hz, CHP), 28.60 (CH2CO), 21.78 (2C,
Ar-CH3) ppm. 31P NMR (162 MHz, CDCl3): δ 31.98 ppm. El-
emental analysis: calcd (%) for C23H20BrO3P: C, 60.68; H,
4.43; Found: C, 60.74; H, 4.46.

Mp = 280 C. H NMR (400 MHz, DMSO-d6): δ = 8.02-7.97
(m, 2H, Ar-H), 7.75-7.69 (m, 2H, Ar-H), 7.67-7.61 (m, 3H, Ar-
H), 7.57-7.54 (m, 1H, Ar-H), 7.49-7.45 (m, 2H, Ar-H), 7.25-
7.21 (m, 1H, Ar-H), 7.05 (d, 1H, J = 8.0 Hz, Ar-H), 6.83 (t, 1H,
J = 7.6 and 7.2 Hz, Ar-H), 6.63 (d, 1H, J = 7.6 Hz, Ar-H), 4.63
(t, 1H, J = 6.4 Hz, -CHP) ppm. HRMS: m/z 351.1119 [M + H]+
calcd for C21H15D2O3PH, found: m/z 351.0903; m/z 373.0939
[M + Na]+ calcd for C21H15D2O3PNa; found: m/z 373.0689.
6-Chloro-4-(di-p-tolylphosphoryl)chroman-2-one
(3r).
White amorphous solid; yield: 90% (37 mg; 0.1 mmol scale);
Mp = 287-288 C. 1HNMR (400 MHz, CDCl3):  = 7.74-7.69
(m, 2H, Ar-H), 7.44-7.34 (m, 4H, Ar-H), 7.26-7.22 (m, 2H, Ar-
H), 7.19-7.16 (m, 1H, Ar-H), 6.94 (d, 1H, J = 8.8 Hz, Ar-H),
6.51-6.49 (m, 1H, Ar-H), 3.81-3.77 (m, 1H, -CHP), 3.17-3.10
(m, 1H, Ha of -CH2CO-), 3.01-2.87 (m, 1H, Hb of -CH2CO-),
2.44 (s, 3H, Ar-CH3), 2.39 (s, 3H, Ar-CH3) ppm. 13C NMR (100
MHz, CDCl3):= 165.18 (d, J = 2 Hz, lactone CO), 151.19 (d,
J3CP = 4 Hz), 143.57 (d, J = 2 Hz, 2C), 131.72 (d, JCP = 9 Hz,
2C), 131.63 (d, JCP = 9 Hz, 2C), 129.95 (d, JCP = 12 Hz, 2C),
129.50 (d, JCP = 12 Hz, 2C), 129.37 (d, JCP = 4 Hz), 129.24 (d,
JCP = 3 Hz), 128.94 (d, JCP = 5 Hz), 125.94 (d, J1CP = 99 Hz),
ASSOCIATED CONTENT
Supporting Information
Scanned copies of 1H-NMR, 13C-NMR, DEPT-135, 31P-NMR and
HMRS spectra for the synthesized 4-(diarylphosphoryl)chroman-
2-one 3 (3a – 3t and 3a-d2) including 2D-NMR (HMQC and
HMBC) for compound 3g, synthetic procedures and 1H-NMR
spectra for deuterated diphenylphosphine oxide-d (2a-d1) and cou-
ramin-3-carboxylic acid-d (1a-d1), and calculations for atom econ-
omy (AE) and E-factors for all the reactions are documented
(PDF).
125.36 (d, J1 = 100 Hz), 119.27 (d, JCP = 5 Hz), 118.87 (d,
CP
JCP = 4 Hz), 38.08 (d, J1 = 64 Hz, CHP), 28.60 (d, J2 = 2
CP
CP
FAIR data, including the primary NMR FID files, for com-
pounds 3a-3t (ZIP)
Hz, CH2CO), 21.78 (2C, Ar-CH3) ppm. 31P NMR (162 MHz,
CDCl3): δ 26.88 ppm. Elemental analysis: calcd (%) for
C23H20ClO3P: C, 67.24; H, 4.91; Found: C, 67.31; H, 4.99.
Notes
6,8-Dibromo-4-(di-p-tolylphosphoryl)chroman-2-one (3s).
The author declares no competing financial interest.
White amorphous solid; yield: 92% (49 mg; 0.1 mmol scale);
Mp = 277-278 C. 1HNMR (400 MHz, CDCl3):  = 7.73-7.68
(m, 2H, Ar-H), 7.59-7.58 (m, 1H, Ar-H), 7.43-7.31 (m, 2H, Ar-
H), 7.38-7.35 (m, 3H, Ar-H), 7.24-7.23 (m, 1H, Ar-H), 6.54-
6.53 (m, 1H, Ar-H), 3.80-3.76 (m, 1H, -CHP), 3.16-3.09 (m,
1H, Ha of -CH2CO-), 3.01-2.88 (m, 1H, Hb of -CH2CO-), 2.44
(s, 3H, Ar-CH3), 2.41 (s, 3H, Ar-CH3) ppm. 13C NMR (100
MHz, CDCl3):= 163.97 (d, JCP = 3 Hz, lactone CO), 148.93
(d, J3CP = 3 Hz), 143.79 (d, J3CP = 3 Hz), 135.25 (d, JCP = 3 Hz,
2C), 131.72 (d, JCP = 10 Hz, 2C), 131.63 (d, JCP = 9 Hz, 2C),
131.43 (d, JCP = 5 Hz), 130.05 (d, JCP = 12 Hz, 2C), 129.58 (d,
ACKNOWLEDGMENT
The author is also thankful to the CSIR, New Delhi for financial
support, and also to IISER, Kolkata for extending HRMS meas-
urement facility.
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This article is protected by copyright. All rights reserved.

10.1002/adsc.202001054
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TOC Graphic
Exploration of a green and efficient strategy for decarboxyla-
tive and regioselective C-4 phosphorylation of coumarin-3-car-
boxylic acids
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