Direct Decarboxylative Allylation and Arylation of Aliphatic Carboxylic Acids Using Flavin-Mediated Photoredox Catalysis

Article abstract of DOI:10.1002/ejoc.201900888

We describe herein a direct decarboxylative allylation of aliphatic carboxylic acids with allylsulfones using visible light and riboflavin tetraacetate (RFTA) as photocatalyst. The reaction proceeds at room temperature tolerating a wide range of functiona

Full text of DOI:10.1002/ejoc.201900888

A Journal of
Accepted Article
Title: Direct decarboxylative allylation and arylation of aliphatic
carboxylic acids using flavin mediated photoredox catalysis
Authors: Nieves P. Ramirez, Teresa Lana-Villarreal, and Jose Carlos
Gonzalez-Gomez
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: Eur. J. Org. Chem. 10.1002/ejoc.201900888
Link to VoR: http://dx.doi.org/10.1002/ejoc.201900888
Supported by

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
Direct decarboxylative allylation and arylation of aliphatic
carboxylic acids using flavin mediated photoredox catalysis
Nieves P. Ramirez,[a] Teresa Lana-Villarreal,[b] and Jose C. Gonzalez-Gomez*[a]
Abstract: We describe herein a direct decarboxylative allylation of aliphatic carboxylic acids with allylsulfones using visible light and riboflavin
tetraacetate (RFTA) as photocatalyst. The reaction proceeds at room temperature tolerating a wide range of functionalities, avoiding the use of
external bases or additives. Mechanistic studies support that alkyl radicals are involved in the reaction, and that a true photocatalytic cycle is
̶
operating. It is proposed that the carboxylic acid is deprotonated by [RFTA]• , and the corresponding carboxylate acts as reductive quencher of
RFTA*, which after decarboxylation produces the alkyl radical. The methodology was adapted to prepare benzothiazoles substituted at C2, by
reacting some carboxylic acids with 2-(phenylsulfonyl)benzothiazole. The number of carboxylic acids suitable for this arylation was lower than
for the allylation and this different reactivity was briefly commented.
for [Ir(dF(CF3)ppy)2(bpy)]PF6: E1/2(*IrIII/IrII) = + 1.32 V vs. SCE)[10]
for this transformation and convenient long excited state lifetimes,
they are very rare and expensive, being organic dyes inexpensive
Introduction
and environmentally friendly alternatives.
In recent years, photoredox catalysis has made important
progresses on the use of visible light energy to activate organic
molecules and promote their reactivity under very mild and
sustainable conditions.[1] In this context, the photocatalytic
oxidation of aliphatic carboxylic acids is a very convenient
approach to generate free radicals, after fast decarboxylation of
the corresponding acyloxy radicals (k ~ 109 s-1 at 25 ºC).[2]
Although other radical precursors have also been successfully
exploited
(e.g.
alkyltrifluoroborates,[3]
silicates,[4]
dihydropyridines,[5] and Katritzky pyridinium salts[6]), carboxylic
acids are ideal starting materials because they are abundant,
inexpensive, stable and some of them are derived from
biomass.[7] The vast majority of photocatalytic decarboxylative
functionalizations of carboxylic acids use bases in stoichiometric
amounts to facilitate the oxidation of the corresponding
carboxylate. This is not surprising if we consider that the oxidation
potential of the carboxylic acid (e.g. for phenylacetic acid
E1/2(RCO2H•+/RCO2H) = +2.51 V vs SCE) is much higher than the
one corresponding to the carboxylate (for tetrabutylammonium
phenylacetate: E1/2(RCO2 /RCO2 ) = +1.27 V vs. SCE).[8] Actually,
functionalized carboxylic acids have been used in a variety of
photocatalytic oxidative transformations of other functional groups,
relying on the fact that the carboxyl group is not oxidizable itself.[9]
In practice, the photocatalytic oxidation of carboxylic acids to
acyloxy radicals usually involves a deprotonation by an external
base, followed by a photoinduced electron transfer (PET) to
strongly oxidizing photocatalysts (Scheme 1a). Although some
iridium photocatalysts have very favorable redox potentials (e.g.
Scheme 1. (a) Photocatalytic oxidation of carboxylic acids with IrIII-derived
photocatalyst. (b) RFTA acting as base and photocatalyst in the photooxidation
of carboxylic acids. (c) Radical addition to allylsulfones or to 2-
(phenylsulfonyl)benzothiazole, followed by elimination of phenyl sulfonyl radical.
•
−
Among different oxidizing organic photocatalysts, we were
particularly attracted by riboflavin (RF),[11] a natural compound
also known as vitamin B2, which is very abundant and responsible
for the redox activity of several flavo-enzymes.[12] Upon visible
light irradiation (λmax ~ 450 nm), RF is excited to its short-lived
singlet state (*S1,  = 6.8 ns) and undergoes an efficient
intersystem crossing (ϕISC = 0.38) to obtain a long-lived triplet
state (*T1,  = 15 s), which is oxidant enough (E1/2 (3RF*/RF•-) =
[a]
M.Sc. N. P. Ramirez, Prof. J. C. Gonzalez-Gomez
Instituto de Síntesis Orgánica y Departamento de Química Orgánica
Universidad de Alicante
+1.50 V vs SCE) to oxidize carboxylates salts (+1.2 V  E1/2

Apdo 99, E-03080 Alicante, Spain
E-mail: josecarlos.gonzalez@ua.es
http://iso.ua.es
+1.5 V vs SCE).[13] Notably, Gilmour’s group reported that
photoexcited RF is able to oxidize cinnamic acids and biaryl
carboxylic acids, in the absence of any external base, to generate
the corresponding carboxyl radical.[14] It was proposed that the
[b]
Prof. T. Lana-Villarreal
Instituto de Electroquímica y Departamento de Química Física
Universidad de Alicante
Supporting information for this article is given via a link at the
end of the document.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
flavin moiety (pKa of RFH• = 8.3 in H2O) can deprotonate the
aliphatic carboxylic acid (pKa ~ 5 in H2O), before the PET, or in a
formal proton-coupled electron transfer (PCET). In line with these
results, MacMillan’s group reported that riboflavin tetrabutyrate
photocatalyzes the decarboxylative alkylation of peptides at the
C-terminal carboxylic acid site more efficiently under mildly acidic
conditions (pH 3.5).[15] Inspired by these findings, we have
developed very recently a protocol in which a riboflavin
tetraacetate (RFTA) acts as base and photocatalyst in the
decarboxylative cyanation of aliphatic carboxylic acids, avoiding
the use of stoichiometric bases.[16] Thus, we decided to extend the
application of this economic, user-friendly and sustainable
protocol to generate alkyl radicals (Scheme 1b) and explore other
organic transformations. It is known that nucleophilic alkyl radicals
are rapidly added to electron-deficient alkenes, generating stable
radical intermediates, that can easily eliminate a sulfonyl radical
from the  position (Scheme 1c).[17] In this context, we planned
to examine the direct decarboxylative allylation of aliphatic
carboxylic acids with allylsulfones using visible light and RFTA
without any other additive. Our interest on this radical allylation
stems from the fact that both substrates- carboxylic acids and allyl
sulfones- are readily available, and the resulting alkene could
serve as a versatile precursor by synthetic manipulations of the
allyl moiety. Moreover, we also decided to examine 2-
(phenylsulfonyl)benzothiazole as radical acceptor to obtain 2-
alkyl benzothiazole derivatives,[18] an heterocyclic family with
multiple bioactivities.[19]
Scheme 2. Precedents in the photocatalytic decarboxylative allylation of
carboxylic acids with allyl sulfones.
Results and Discussion
As in our previous communication, we have chosen RFTA [23] as
the photocatalyst for this study because it shows better solubility
in organic solvents, greater photostability and is less likely than
RF to form aggregates through hydrogen bonding interactions.[24]
A
key feature in our redox-neutral visible light-promoted
decarboxylative allylation of carboxylic acids with allylsulfones is
the turnover of the RFTA catalyst with the phenyl sulfonyl radical
•
(PhSO2 ). In our reaction design, (Scheme 3) a formal proton-
coupled electron transfer between the photoexcited RFTA* and
the carboxylic acid would explain the generation of alkyl radicals
in the absence of base. Alternatively, it is plausible that a small
̶
fraction of in situ formed [RFTA]• deprotonates the carboxylic
acid to give the corresponding carboxylate,[25] which in turn would
be oxidized by the long-lived triplet-excited state of the flavin,
generating the alkyl radical after rapid decarboxylation.[26] The
addition of alkyl radicals to electron-deficient allylsulfones should
be relatively fast (k ~ 106 M-1s-1),[20] and must be followed by a
radical fragmentation to obtain the desired alkene. In the same
event is produced the stabilized phenyl sulfonyl radical, which is
•
-
easily reduced [E1/2(PhSO2 /PhSO2 ) = +0.50 V vs SCE][27] by the
hydroflavin radical [E1/2(RFTA/RFTAH•) ≈ -0.60 V vs SCE],[28]
thereby closing the catalytic cycle after proton transfer. According
to the redox potentials involved, this electron transfer is highly
exergonic (∆퐺퐸푇 ≈ −25 푘푐푎푙/푚표푙). However, we can not rule out
a hydrogen atom abstraction by phenyl sulfonyl radical from the
hydroflavin radical to complete the photoredox neutral catalytic
cycle.
A
fast and chemoselective photocatalytic decarboxylative
allylation was recently developed (Scheme 2a), but using N-
acyloxyphthalimides, [Ru(bpy)3](PF6)2 as photocatalyst and
stoichiometric amounts of reductants.[20] The silver catalyzed
direct decarboxylative allylation of carboxylic acids (Scheme 2b)
was also recently developed, showing broad substrate scope, but
in this case K2S2O8 was required in stoichiometric amounts to
regenerate the Ag(II) catalyst.[21] The direct photocatalytic
allylation of carboxylic acids via a redox-neutral process was not
developed until very recently using Ir(ppy)2(bpy)PF6 as catalyst,
and stoichiometric amounts of Cs2(CO3), although it was limited
to N-arylglycine derivatives (Scheme 2c).[22] Herein we report our
results on the direct and redox-neutral photocatalytic allylation of
carboxylic acids (Scheme 2d).
Scheme 3. Plausible mechanism for our photocatalytic decarboxylative
allylation of carboxylic acids.
Our studies began using 2-phenoxypropanoic acid (1a) and butyl
2-((phenylsulfonyl)methyl)acrylate (2a) as model substrates to
screen different conditions for the decarboxylative allylation
reaction (Table 1). When the reaction was performed using
degassed MeCN (argon sparging over 10 min) and RFTA (5
mol-%) as photocatalyst, under irradiation with blue LEDs (λmax
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
455 nm, 15 ± 2 mW/cm2) at room temperature, the desired
product 3aa was obtained in 77% yield after 22 h (entry 1).
Notably, using a higher load of RFTA (entry 2) did not provide any
significant advantage over the previous conditions. Moreover,
other solvent systems (entries 3 and 4) or the addition of an
organic base (entry 5) in stoichiometric amount had a deleterious
effect on the product yield. Incomplete conversion was observed
when the reaction was run for only 8 h (entry 6). Furthermore,
when the reaction was not degassed, product 3aa was also
transform the alanine derivatives in useful synthetic yields. We
also explored a few non-activated α-C carboxylic acids, but only
the tertiary adamantly carboxylic acid gave product 3qa in
moderate yield. The cyclohexyl- and sec-butyl carboxylic acids
failed to give the desired products in significant amounts.
obtained in
a diminished yield (entry 7). Finally, control
experiments revealed that both the light and the photocatalyst are
required to the reaction takes place (entries 8 and 9). It is worth
of note that although the allyl sulfone is frequently used in large
excess (3 – 4 equiv) to minimize other competing reactions, we
have optimized our reaction using an almost perfect stoichiometry.
Table 1. Optimization of the decarboxylative allylation.
Entry
Modification from standard
conditions
Yield (%)[a]
1
2
3
4
5
6
7
8
9
none
77
78
41
33
27
46
44
0
RFTA (10 mol-%)
In MeCN/H2O (2:1)
In MeOH
DABCO (1 equiv)
8 h
No degassing
No photocatalyst
No light
0
Scheme 4. Scope of carboxylic acids on the decarboxylative allylation. [a]
Yields are reported for isolated pure products at 0.25 mmol scale. [b] After 24 h,
another 5 mol-% of RFTA was added and the reaction was run over 12 h.
[a] Yield determined by GC using adamantane as internal standard.
Under our optimized reaction conditions, we examined different
carboxylic acids with allylsulfone 2a (Scheme 4). We were
pleased to observe that different α-oxo carboxylic acids- including
secondary, tertiary and even primary- were suitable substrates,
giving the desired products (3aa–3ia) from moderate to good
yields. Interestingly, the ribosic acid derivative afforded the
desired product 3ha in good yield as a single isomer with retention
of the configuration,[29] although a longer time and two portions of
5 mol-% of photocatalyst were required. Moreover, an α-
benzyloxy carboxylic acid was also tolerated with the catalytic
protocol, although the corresponding product 3ia was obtained in
relatively low yield. Remarkably, an α-thio- carboxylic acid was
also compatible under the reaction conditions, giving the desired
product 3ja in good yield, despite different possible parasitic
reactions (e.g. overoxidation, homocoupling of intermediate
radicals, hydrodecarboxylation, etc). In addition, an α-ketoacid
was also a suitable substrate affording the desired ketone 3ka in
a moderate yield. N-arylglycine derivatives were also well
tolerated under the optimized conditions and the corresponding
products (3la-3oa) were obtained from moderate to good yields.
Similarly, a pyrrole-derived carboxylic acid afforded the desired
product 3pa in good yield. Unfortunately, other common N-
protecting groups, such as Boc and Cbz, were not suitable to
We also examined the scope of different allylsulfones under our
optimized conditions, using 2-phenoxypropanoic acid as model
substrate (Scheme 5). Terminal allylsulfones with different ester
groups, including ethyl, benzyl, and allyl esters were compatible
with this protocol, giving the corresponding products (3ab-3ad) in
good yields. Other electron-withdrawing groups were also well
tolerated in the terminal allylsulfones, such as chloro and
phenylsulfone, giving the desired compounds 3ae and 3af in good
yields. In addition, an electron-richer 2-phenylallylsulfone was
also a suitable partner, likely by resonance stabilization of the
benzylic radical intermediate, to provide product 3ag in a
moderate yield. Moreover, internal allyl sulfone 2h was also tested,
obtaining the terminal alkene 3ah in low yield after a difficult
purification, as a 2:1 mixture of diastereoisomers. This result
supports a regioselective alkyl radical addition to the double bond
of the allyl sulfone, followed by -elimination of the sulfonyl radical
(SH2’ pathway). Remarkably, the mild reaction conditions used
were compatible with a broad range of functionalities, including:
esters, ethers, phenyl rings, chloro substituents, ketals, thioethers,
ketones, N-aryl amines, pyrroles, allyl groups, benzyl groups,
sulfones and cyano groups.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
photoexcited catalyst was not altered in the presence of 2a
(Scheme 7c, details can be found in the supporting information).
Finally, the quantum yield of the reaction of 1b and 2a resulted
very low (Scheme 7d), supporting a closed photocatalytic cycle
instead of a radical chain propagation.[32]
Scheme 5. Allyl sulfone scope with carboxylic acid 1a. [a] Yields are reported
for isolated pure products at 0.25 mmol scale. [b] 2 equiv of 1a were used. [c]
Determined by 1H-NMR.
To examine the synthetic utility of our direct decarboxylative
allylation, we carried out the preparation of compound 3ba at 2
mmol scale under batch conditions (Scheme 6). Although the
product was obtained in a synthetically useful yield (48%), a
significant decreased was observed compared to the reaction at
0.25 mmol (68%).[30] Moreover, to show that the allyl moiety can
also serve as a radical acceptor, we conducted the Giese
decarboxylative alkylation using reaction conditions previously
developed in our group.[31] Under these conditions, when
carboxylic acid 1d was employed, compound 6 was obtained in
an unoptimized 45% yield.
Scheme 7. Mechanistic studies.
We thus re-examined the reaction conditions to adapt our protocol
for the decarboxylative arylation of aliphatic carboxylic acids,
using 1b and 2-(phenylsulfonyl)benzothiazole (4) as substrates
(Table 2). Under the same allylation conditions the desired
compound 5b was obtained in moderate yield (entry 1). When 2
equivalents of the carboxylic acid were used, the reaction yield
was slightly improved (entry 2). Different solvent systems were
also examined to facilitate the solubility of the aryl sulfone at the
beginning of the reaction, but none of them furnished the desired
product in a better yield (entries 3-5). Finally, when the load of
photocatalyst was increased to 10 mol-% and the reaction was
run over 36 h, the best result was obtained (entry 6). Notably, this
reaction is slower than the allylation, likely by a higher steric
demand in the addition of the alkyl radical to the carbon atom next
to the bulky sulfonyl group. It is worth saying that we recognized
that a possible solution to this problem would be the C2-alkylation
of unsubstituted benzothiazoles, thereby less sterically hindered
and more easily available starting materials.[33] However, the
reaction of 1b with benzothiazole, using RFTA (10 mol-%) and air
as terminal oxidant gave only traces of product 5b (not shown).
Scheme 6. Preparation of 3ba at 2 mmol scale and Giese decarboxylative
alkylation with carboxylic acid 1d.
Evidence for the free radical involvement in these reactions
follows from the observed inhibitory effect of TEMPO ((2,2,6,6-
tetramethylpiperidin-1-yl)oxyl, Scheme 7a) on the allylation
reaction. Eventually, the corresponding radical was trapped by
TEMPO on this experiment to form adduct 1b-TEMPO, which was
detected by LC-MS. Additionally, when carboxylic acid 1q was
submitted to the allylation conditions with sulfone 2a, the expected
compound 3oa was isolated, but also compound 7 from a fast 5-
exo-trig radical addition followed by the allylation reaction
(Scheme 7b). In order to support the proposed mechanism, it was
also checked that carboxylic acid 1b was an efficient quencher of
RFTA* luminescence’s, while the emission intensity of the
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
observed that α-thio-, tertiary α-oxo- and α-keto carboxylic acids
were successful in the decarboxylative allylation, but not in the
arylation reaction. It is evident that most successful carboxylic
acids in these reactions have an α-substituent that stabilizes the
radical by resonance, thereby increasing the energy of the SOMO
and their reactivity with electron-deficient radical acceptors. From
Kochi’s work it is known that decarboxylation (kdec) of arylacetoxy
radicals generated via PET in carboxylate ion pairs lies in the
range of ퟏퟎퟗ 풔−ퟏ, competing with very fast back-electron transfer
(kBET ~ퟏퟎퟏퟏ 풔−ퟏ ).[2] In this study was also concluded that
decarboxylation of α-oxo benzylic carboxylic acids to provide
stabilized benziloxy radicals is extremely fast (kdec ~ퟏퟎퟏퟏ 풔−ퟏ ).
We thus reasoned that the success of these reactions depends
on an extremely fast decarboxylation to override the back-
electron transfer. It is also important the use of very electrophilic
radical acceptors (with low steric demand) that rapidly trap the
generated radical (in very low concentration), whereas the
sulfonyl radical is produced to regenerate the RFTA and reset a
new catalytic cycle. From the simplified picture depicted in
Scheme 9 it is also possible to anticipate that, if the reaction of
the generated radical is not fast (kR1 or kR2), the hydrogen atom
Table 2. Re-examining reaction conditions for the decarboxylative arylation.
Entry
Modification from standard conditions
none
2 equiv of 1b and 1 equiv of 4
As in entry 2, but in 9:1 MeCN/EtOH
As in entry 2, but in EtOH
Yield (%)a
1
2
3
4
5
6
52
60
60
50
52
As in entry 2, but in acetone
entry 2, but 10 mol-% of RFTA and 36 h
64 (95)[b]
[a]
[b]
Yields determined for isolated pure products.
compound 4.
Based on recovered
Having identified reasonably good reaction conditions, we
screened some aliphatic carboxylic acids in the homolytic
aromatic substitution (HAS) of 2-(phenylsulfonyl)benzothiazole
(Scheme 8). As in the decarboxylative allylation, α-oxo carboxylic
acids were suitable substrates in this transformation, obtaining
the products 5a-5e in yields from moderate to good. It is worth
noting that during the formation of compound 5d it was also
observed the homocoupling of the corresponding radicals by GC-
MS. In the case of compound 5e the yield was also rather low,
most likely due to a higher steric hindrance with the bulky radical
involved in the transformation. Finally, the C2-α-aminomethylation
of benzothiazole was accomplished using N-phenylglycine in our
reaction conditions to obtain 5f in good yield. Other carboxylic
acids, such as: clofibric acid (1c), 2-(p-tolylthio)acetic acid (1j) and
phenoxyacetic acid (1e) failed to give the desired benzothiazole,
observing mainly the corresponding hydrodecarboxylation by GC-
MS. Moreover, N-Boc phenylalanine gave only traces of the
desired benzothiazole.
abstraction
from
RFTAH•
would
be
possible
(hydrodecarboxylation) or even deactivation of the catalyst by
radical-radical coupling.
Scheme 9. Different reactivity of carboxylic acids with the radical acceptors
used.
Conclusions
In conclusion, we have demonstrated that the direct
decarboxylative allylation of carboxylic acids with allylsulfones
can be efficiently promoted at room temperature by visible light,
using inexpensive RFTA as photocatalyst in the absence of base.
The transformation is redox-neutral, avoiding the use of external
additives and none of the reagents was used in large excess.
Importantly, although the carboxylic acids required a heteroatom
or a carbonyl group in the α-position, the mild reaction conditions
used tolerate the presence of a wide range of functionalities.
Moreover, some carboxylic acids were also successfully used
under similar conditions in the decarboxylative homolytic aromatic
substitution of 2-(phenylsulfonyl)benzothiazole, to obtain C2-
substituted benzothiazoles in moderate to good yields.
Scheme 8. Carboxylic acids scope in the HAS of 4. [a] Yields are reported for
isolated pure products at 0.25 mmol scale.
In our previous decarboxylative cyanation with TsCN, using RFTA
as base and photocatalyst, the range of successful carboxylic
acids was broader, being α-N carbamates and non-activated α-C
carboxylic acids also suitable substrates.[16] In this work, we have
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
13C-NMR (75 MHz, CDCl3) δ 166.9 (C), 143.3 (C), 143.1 (C), 135.6 (C),
128.5 (CH2), 121.7 (CH), 121.4 (CH), 117.5 (CH), 117.2 (CH), 71.5 (CH),
67.4 (CH2), 65.0 (CH2), 33.8 (CH2), 30.8 (CH2), 19.4 (CH2), 13.6 (CH3)
ppm; GC RT 12.44 min; LRMS (EI) m/z (%) = 276 (M+, 28), 135 (100), 134
(10), 121 (12), 111 (16), 110 (11); HRMS (EI) Calcd. for C16H20O4
276.1362, found 276.1363.
Experimental Section
General Remarks: Reagents and solvents were purchased from different
trading houses and were used without further purification, unless
otherwise stated. Riboflavin Tetraacetate (RFTA) was prepared from
commercial (-)-Riboflavin according to a reported procedure.[23] TLCs were
performed on silica gel 60 F254, using aluminium plates and visualized by
exposure with UV or stain with PMA (KMnO4.for compound 3qa). Flash
chromatographies (FC) were carried out on handpacked columns of silica
gel 60 (230 – 400 mesh). Infrared (IR) analysis was performed with a
JASCO FT/IR 4100 spectrophotometer equipped with an ATR component.
LRMS were performed in an AGILENT 6890N mass spectrometer coupled
with a gas chromatographer (GC); the mobile phase was helium (2
mL/min); HP-1 column of 12 m was used; temperature program starts at
80 ºC for 3 min, then up to 270 ºC with a rate of 15 ºC/min, and 10 min at
270 ºC, using the Electron Impact (EI) mode at 70 eV (unless otherwise
indicated). HRMS analyses were carried out in an AGILENT 7200 using
the Electron Impact (EI) mode at 70 eV by Q-TOF .1H-NMR spectra were
recorded at 300 or 400 MHz for 1H-NMR and 75 or 101 MHz for 13C NMR,
using CDCl3 as the solvent and referenced to CDCl3 (unless otherwise
indicated). 13C NMR spectra were recorded with 1H-decoupling at 100 MHz
and referenced to CDCl3 at 77.16 ppm. Reactions were irradiated in a
PhotoRedOx Box Duo (EvoluchemTM) equipped with two lamps LED
CREE XPE 18W (450-455 nm).
Butyl 4-(4-chlorophenoxy)-4-methyl-2-methylenepentanoate (3ca):
Compound
3ca
was
prepared
from
2-(4-Chlorophenoxy)-2-
methylpropanoic acid (Clofibric Acid) (1c)[35] following the general
procedure. It was purified by FC (100% Hexane to 95:5 Hexane/EtOAc)
and obtained as a pale-yellow oil (47 mg, 0.15 mmol, 60%): TLC Rf 0.65
(95:5 Hexane/EtOAc); IR ν 2969, 2939, 2878, 1721, 1625, 1584, 1488,
1482, 1223, 1173, 1152, 1093, 949, 850, 814, 751 cm-1; 1H-NMR (300 MHz,
CDCl3) δ 7.24 - 7.17 (m, 2H), 6.93 - 6.85 (m, 2H), 6.28 (d, J = 1.7 Hz, 1H),
5.71 - 5.66 (m, 1H), 4.15 (t, J = 6.6 Hz, 2H), 2.75 (s, 2H), 1.71 - 1.57 (m,
2H), 1.46 - 1.34 (m, 2H), 1.24 (s, 6H), 6.93 (t, J = 7.3 Hz, 3) ppm; 13C-NMR
(101 MHz, CDCl3) δ 168.1 (C), 153.9 (C), 137.6 (C), 129.0 (2 х CH), 128.7
(C), 128.2 (CH2), 125.3 (2 х CH), 80.7 (C), 64.9 (CH2), 43.4 (CH2), 30.8
(CH2), 26.2 (2 х CH3), 19.3 (CH2), 13.8 (CH3) ppm; GC RT 12.78 min;
LRMS (EI) m/z (%) = 183 (M+ - C6H4ClO, 13), 169 (11), 130 (29), 128 (88),
127 (40), 126 (100), 125 (15), 111 (32), 109 (32), 108 (27), 81 (100), 80
(31), 79 (40), 67 (11), 65 (23), 63 (10), 57 (11), 53 (15); HRMS (EI) Calcd.
for C17H23ClO3 310.1336, found 310.1327.
Butyl 2-methylene-4-(p-tolyloxy)butanoate (3da): Compound 3da was
prepared from 2-(p-Tolyloxy)acetic acid (1d) following the general
procedure. It was purified by FC (100% Hexane to 95:5 Hexane/EtOAc)
and obtained as a colorless oil (53 mg, 0.20 mmol, 80%): TLC Rf 0.41 (95:5
Hexane/EtOAc); IR ν 2988, 2956, 2934, 2871, 1740, 1714, 1511, 1372,
1235, 1160, 1046, 1045, 817 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.07 (d,
J = 9.2 Hz, 2H), 6.80 (d, J = 8.6 Hz, 2H), 6.28 (d, J = 1.3 Hz, 1H), 5.70 (dd,
J = 2.5, 1.2 Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H), 4.08 (t, J = 6.6 Hz, 2H), 2.78
(td, J = 6.6, 0.8 Hz, 2H), 2.28 (s, 3H), 1.71 - 1.60 (m, 2H), 1.47 - 1.35 (m,
2H), 0.94 (t, J = 7.3 Hz, 3H) ppm; 13C-NMR (101 MHz, CDCl3) δ 167.1 (C),
156.7 (C), 137.1 (C), 130.1 (C), 130.0 (2 × CH), 127.2 (CH2), 114.6 (2 ×
CH), 66.4 (CH2), 64.9 (CH2), 32.1 (CH2), 30.8 (CH2), 20.6 (CH3), 19.4
(CH2), 13.9 (CH3) ppm; GC RT 11.82 min; LRMS (EI) m/z (%) = 262 (M+,
2), 155 (17), 108 (21), 107 (13), 99 (100), 91 (14), 81 (11), 77 (10), 53 (11);
HRMS (EI) Calcd. for C16H22O3 262.1569, found 262.1563.
General procedure for the decarboxylative allylation of carboxylic
acids: The corresponding carboxylic acid (0.25 mmol) was added to a 2
dram vial, followed by RFTA (6.8 mg, 0.0125 mmol, 5 mol-%), and a
solution of 2 (0.275 mmol, 1.1 equiv) in MeCN (2.5 mL). Then, the vial was
sealed with a septum and the reaction mixture was degassed by sparging
with Ar for 10 min. Finally, the vial was equipped with an Ar balloon and
the yellow homogeneous solution was stirred at 25 ºC under blue LEDs
irradiation (λ = 455 nm, 15 ± 2 mW/cm2)[34] until full conversion or no
progress of the reaction was observed by TLC or GC (generally 18 - 22 h).
The solvent was removed under reduced pressure, affording a residue
which was purified by FC.
Butyl 2-methylene-4-phenoxypentanoate (3aa): Compound 3aa was
prepared from 2-Phenoxypropanoic acid (1a) following the general
procedure. It was purified by FC (100% Hexane to 90:10 Hexane/EtOAc)
and obtained as a colorless oil (51 mg, 0.19 mmol, 77%): TLC Rf 0.54
(95:5 Hexane/EtOAc); IR ν 3014, 1712, 1639, 1591, 1489, 1237, 1214,
1157, 746 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.30 - 7.23 (m, 2H), 6.95 -
6.89 (m, 3H), 6.24 (d, J = 1.5 Hz, 1H), 5.67 (dd, J = 2.5, 1.2 Hz, 1H), 4.61
(h, J = 6.2 Hz, 1H), 4.16 (t, J = 6.6 Hz, 2H), 2.83 (ddd, J = 13.9, 6.6, 1.0
Hz, 1H), 2.50 (ddd, J = 13.9, 6.3, 0.9 Hz, 1H), 1.71 - 1.61 (m, 2H), 1.46 -
1.34 (m, 2H), 1.31 (d, J = 6.1 Hz, 3H), 0.94 (t, J = 7.3 Hz, 1H) ppm; 13C-
NMR (101 MHz, CDCl3) δ 167.3 (C), 158.0 (C), 137.2 (C), 129.6 (2 х CH),
128.0 (CH2), 120.7 (CH), 116.0 (2 х CH), 72.1 (CH), 64.9 (CH2), 39.3 (CH2),
19.8 (CH3), 19.4 (CH2), 13.9 (CH3) ppm; GC RT 11.15; LRMS (EI) m/z (%)
= 262 (M+, 2), 169 (34), 121 (18), 113 (100), 95 (33), 94 (39), 87 (12), 67
(19); HRMS (EI) Calcd. for C16H22O3 - C7H9O 153.0916, found 153.0913.
Butyl 2-methylene-4-phenoxybutanoate (3ea): Compound 3ea was
prepared from 2-Phenoxyacetic acid (1e), following the general procedure,
but in this case 40 h of reaction were required. It was purified by FC (100%
Hexane to 90:10 Hexane/EtOAc) and obtained as a colorless oil (32 mg,
0.13 mmol, 50%): TLC Rf 0.65 (95:5 Hexane/EtOAc); IR ν 2824, 1713,
1598, 1498, 1471, 1294, 1241, 1208, 1160, 1020, 949, 815, 799, 753, 692
cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.33 - 7.23 (m, 2H), 6.99 - 6.84 (m, 3H),
6.28 (d, J = 1.2 Hz, 1H), 5.72 (d, J = 1.2 Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H),
4.12 (t, J = 6.6 Hz, 2H), 2.80 (td, J = 6.6, 0.8 Hz, 2H), 1.76 - 1.62 (m, 2H),
1.41 (dq, J = 14.5, 7.3 Hz, 2H), 0.95 (t, J = 7.4 Hz, 3H) ppm; 13C-NMR (101
MHz, CDCl3) δ 167.1 (C), 158.8 (C), 137.1 (C), 129.6 (2 × CH), 127.3 (CH2),
120.9 (CH), 114.7 (2 × CH), 66.3 (CH2), 64.9 (CH2), 32.1 (CH2), 30.8 (CH2),
19.4 (CH2), 13.9 (CH3) ppm; GC RT 13.32 min; LRMS (EI) m/z (%) = 248
(M+, 3), 155 (28), 99 (100), 94 (18), 81 (12), 77 (12); HRMS (EI) Calcd. for
C15H20O3 248.1412, found 248.1402.
Butyl 2-((2,3-dihydrobenzo[b][1,4]dioxin-2-yl)methyl)acrylate (3ba):
Compound 3ba was prepared from 1,4-Benzodioxane-2-carboxylic acid
(1b) following the general procedure. It was purified by FC (100% Hexane
to 95:5 Hexane/EtOAc) and obtained as a pale-yellow oil (47 mg, 0.17
mmol, 68%): TLC Rf 0.57 (95:5 Hexane/EtOAc); IR ν 2980, 2957, 2934,
1716, 1381, 1274, 1244, 1210, 1193, 1156, 1146, 1105, 1091, 1060, 960,
869, 755, 696 cm-1; 1H-NMR (300 MHz, CDCl3) δ 6.89 - 6.81 (m, 4H), 6.33
(d, J = 1.3 Hz, 1H), 5.73 (d, J = 1.2 Hz, 1H), 4.41 - 4.32 (m, 1H), 4.24 (dd,
J = 11.3, 2.3 Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H), 3.93 (dd, J = 11.3, 6.8 Hz,
1H), 2.72 (ddd, J = 14.3, 7.5, 0.8 Hz, 1H), 2.64 (ddd, J = 14.3, 5.8, 0.9 Hz,
1H), 1.72 - 1.62 (m, 2H), 1.47 - 1.35 (m, 2H), 0.95 (t, J = 7.3 Hz, 3H) ppm;
Butyl 4-(4-chlorophenoxy)-2-methylenebutanoate (3fa): Compound
3fa was prepared from 2-(4-chlorophenoxy)acetic acid (1f) following the
general procedure. It was purified by FC (100% Hexane to 90:10
Hexane/EtOAc) and obtained as a colorless oil (28 mg, 0.10 mmol, 40%):
TLC Rf 0.60 (95:5 Hexane/EtOAc); IR ν 2958, 2934, 2871, 1713, 1631,
1596, 1579, 1493, 1471, 1281, 1241, 1210, 1159, 1033, 822 cm-1; 1H-NMR
(300 MHz, CDCl3) δ 7.22 (d, J = 9.0 Hz, 2H), 6.82 (d, J = 9.0 Hz, 2H), 6.28
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
(d, J = 1.2 Hz, 1H), 5.70 (d, J = 1.2 Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H), 4.08
(t, J = 6.6 Hz, 2H), 2.78 (td, J = 6.6, 0.8 Hz, 2H), 1.71 - 1.62 (m, 2H), 1.41
(dq, J = 14.4, 7.3 Hz, 2H), 0.94 (t, J = 7.3 Hz, 3H) ppm; 13C-NMR (101
MHz, CDCl3) δ 167.0 (C), 157.5 (C), 136.9 (C), 129.4 (2 × CH), 125.7 (C),
116.0 (2 × CH), 66.7 (CH2), 64.9 (CH2), 32.1 (CH2), 30.8 (CH2), 19.4 (CH2),
13.9 (CH3) ppm; GC RT 12.47 min; LRMS (EI) m/z (%) = 282 (M+, 3), 155
(21), 128 (15), 99 (100), 81 (10); HRMS (EI) Calcd. for C15H19ClO3
282.1023, found 282.1000.
Butyl 2-methylene-4-(p-tolylthio)butanoate (3ja): Compound 3ja was
prepared from 2-(p-Tolylthio)acetic acid (1j)[20] following the general
procedure. It was purified by FC (100% Hexane to 90:10 Hexane/EtOAc)
and obtained as a colorless oil (45 mg, 0.16 mmol, 65%): TLC Rf 0.65 (95:5
Hexane/EtOAc); IR ν 2962, 2936, 2874, 1710, 1634, 1489, 1177, 1173,
1124, 947, 803 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.27 (d, J = 8.0 Hz, 2H),
7.10 (d, J = 8.0 Hz, 2H), 6.21 (d, J = 1.2 Hz, 1H), 5.58 (d, J = 1.2 Hz, 1H),
4.14 (t, J = 6.6 Hz, 2H), 3.04 (t, J = 7.7 Hz, 2H), 2.61 (t, J = 7.5 Hz, 2H),
2.32 (s, 3H), 1.69 - 1.60 (m, 2H), 1.46 - 1.33 (m, 2H), 0.94 (t, J = 7.3 Hz,
3H) ppm; 13C-NMR (101 MHz, CDCl3) δ 166.9 (C), 138.9 (C), 136.3 (C),
132.3 (C), 130.2 (2 × CH), 129.8 (2 × CH), 126.6 (CH2), 64.8 (CH2), 33.2
(CH2), 32.4 (CH2), 30.8 (CH2), 21.1 (CH3), 19.4 (CH2), 13.9 (CH3) ppm; GC
RT 12.85min; LRMS (EI) m/z (%) = 278 (M+, 35), 205 (10), 137 (100), 124
(10), 99 (82), 91 (18); HRMS (EI) Calcd. for C16H22O2S 278.1341, found
278.1350.
Butyl 4-(2-methoxyphenoxy)-2-methylenebutanoate (3ga): Compound
3ga was prepared from 2-(2-methoxyphenoxy)acetic acid (1g) following
the general procedure. It was purified by FC (100% Hexane to 90:10
Hexane/EtOAc) and obtained as a pale-yellow oil (38 mg, 0.14 mmol,
55%): TLC Rf 0.38 (95:5 Hexane/EtOAc); IR ν 2962, 1716, 1631, 1501,
1253, 1250, 1226, 1157, 1123, 1028, 742 cm-1; 1H-NMR (300 MHz, CDCl3)
δ 6.98 - 6.85 (m, 4H), 6.29 (d, J = 1.3 Hz, 1H), 5.74 (dd, J = 2.4, 1.2 Hz,
1H), 4.18 (dd, J = 6.8, 2.2 Hz, 2H), 4.16 (dd, J = 6.8, 1.8 Hz, 2H), 3.86 (s,
3H), 2.85 (td, J = 7.0, 0.9 Hz, 2H), 1.71 - 1.61 (m, 2H), 1.41 (dq, J = 14.4,
7.3 Hz, 2H), 0.94 (s, 3H) ppm; 13C-NMR (101 MHz, CDCl3) δ 167.1 (C),
149.7 (C), 148.4 (C), 137.0 (C), 127.5 (CH2), 121.4 (CH), 121.1 (CH),
113.7 (CH), 112.2 (CH), 67.7 (CH2), 64.9 (CH2), 56.1 (CH3), 32.1 (CH2),
30.8 (CH2), 19.4 (CH2), 13.9 (CH3) ppm; GC RT 14.34 min; LRMS (EI) m/z
(%) = 278 (M+, 1%), 155 (21), 124 (14), 109 (11), 99 (100), 81 (11); HRMS
(EI) Calcd. for C16H22O4 278.1518, found 278.1521.
Butyl 2-methylene-4-oxo-4-phenylbutanoate (3ka): Compound 3ka
was prepared from 2-Oxo-2-phenylacetic acid (1k) following the general
procedure. It was purified by FC (100% Hexane to 85:15 Hexane/EtOAc)
and obtained as a pale-yellow oil (30 mg, 0.12 mmol, 48%): TLC Rf 0.32
(95:5 Hexane/EtOAc); IR ν 2970, 1713, 1685, 1325, 1303, 1212, 1147,
910, 752, 730 cm-1; 1H-NMR (300 MHz, CDCl3) δ 8.01 - 7.95 (m, 2H), 7.63
- 7.53 (m, 1H), 7.51 - 7.43 (m, 2H), 6.40 (d, J = 1.0 Hz, 1H), 5.69 (d, J =
1.1 Hz, 1H), 4.15 (t, J = 6.6 Hz, 2H), 3.99 (d, J = 0.8 Hz, 2H), 1.68 - 1.54
(m, 2H), 1.35 (dq, J = 14.4, 7.3 Hz, 2H), 0.89 (t, J = 7.3 Hz, 3H) ppm; 13C-
NMR (101 MHz, CDCl3) δ 197.0 (C), 166.6 (C), 136.7 (C), 135.0 (C), 133.4
(CH), 128.8 (2 × CH), 128.5 (CH2), 128.4 (2 × CH), 65.0 (CH2), 41.8 (CH2),
30.7 (CH2), 19.3 (CH2), 13.8 (CH3) ppm; GC RT 13.71 min; LRMS (EI) m/z
(%) = 173 (M+ - C4H9O, 7), 172 (12), 106 (8), 105 (100), 77 (28); HRMS
(EI) Calcd. for C15H18O3 246.1256, found 246.1245.
Butyl
2-((3aR,6R,6aR)-6-methoxy-2,2-dimethyltetrahydrofuro[3,4-
d][1,3-dioxol-4-yl)methyl)acrylate (3ha): Compound 3ha was prepared
from 2,3-O-isopropylidene-1-O-methyl-D-ribosic acid (1h) following the
general procedure. In this case, after 24 h, another 5 mol-% of RFTA was
added and the reaction was run for another 12 h. It was purified by FC
(100% Hexane to 90:10 Hexane/EtOAc) and obtained as a yellow oil (57
mg, 0.18 mmol, 70%, single diastereoisomer): TLC Rf 0.25 (94:5
Hexane/EtOAc); IR ν 2976, 2961, 2939, 1715, 1379, 1266, 1244, 1208,
1187, 1154, 1144, 1105, 1090, 1058, 960, 871, 695 cm-1; 1H-NMR (300
MHz, CDCl3) δ 6.29 (d, J = 1.1 Hz, 1H), 5.67 (q, J = 1.2 Hz, 1H), 4.95 (s,
1H), 4.60 (dd, J = 14.0, 6.2 Hz, 2H), 4.44 (td, J = 7.6, 0.5 Hz, 1H), 4.16 (t,
J = 6.6 Hz, 2H), 3.33 (s, 3H), 2.59 (d, J = 7.7 Hz, 2H), 1.73 - 1.60 (m, 2H),
1.47 (s, 3H), 1.44 - 1.37 (m, 2H), 1.30 (s, 3H), 0.94 (t, J = 7.3 Hz, 3H) ppm;
13C-NMR (75 MHz, CDCl3) δ 166.9 (C), 137.1 (C), 127.4 (CH2), 112.5 (C),
109.9 (CH), 85.6 (CH), 85.5 (CH), 83.8 (CH), 64.9 (CH2), 55.2 (CH3), 37.4
(CH2), 30.8 (CH2), 26.6 (CH3), 25.2 (CH3), 19.4 (CH2), 13.9 (CH3) ppm; GC
RT 11.64 min; LRMS (EI) m/z (%) = 299 (M+ - CH3, 17), 211 (18), 196 (25),
174 (10), 173 (100), 171 (10), 169 (33), 141 (11), 140 (16), 139 (12), 123
(12), 122 (14), 119 (26), 117 (29), 116 (10), 115 (29), 97 (18), 95 (34), 94
(11), 87 (19), 85 (23), 59 (28), 58 (11), 57 (17), 55 (16); HRMS (EI) Calcd.
for C16H26O6 314.1729, found 314.1727.
Butyl 2-methylene-4-(phenylamino)butanoate (3la): Compound 3la
was prepared from (N)-Phenylglycine (1l) following the general procedure.
It was purified by FC (100% Hexane to 90:10 Hexane/EtOAc) and obtained
as a colorless oil (39 mg, 0.15 mmol, 60%): TLC Rf 0.29 (95:5
Hexane/EtOAc); IR ν 2969, 2901, 1707, 1603, 1508, 1215, 1066, 908, 754,
731 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.23 - 7.14 (m, 2H), 6.73 (t, J = 7.3
Hz, 1H), 6.67 (d, J = 7.7 Hz, 2H), 6.25 (d, J = 1.3 Hz, 1H), 5.63 (d, J = 1.2
Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H), 3.31 (t, J = 6.8 Hz, 2H), 2.64 (td, J = 6.8,
0.7 Hz, 2H), 1.77 - 1.59 (m, 2H), 1.43 - 1.40 (m, 2H), 0.95 (t, J = 7.3 Hz,
3H) ppm; 13C-NMR (101 MHz, CDCl3) δ 167.2 (C), 147.5 (C), 138.3 (C),
129.4 (2 × CH), 126.9 (CH2), 118.0 (CH), 113.5 (2 × CH), 65.0 (CH2), 43.4
(CH2), 32.0 (CH2), 30.8 (CH2), 19.4 (CH2), 13.9 (CH3) ppm; GC RT 11.99
min; LRMS (EI) m/z (%) = 247 (M+, 14), 173 (24), 106 (100), 105 (15), 104
(11), 77 (21); HRMS (EI) Calcd. for C15H21NO2 247.1572, found 247.1565.
Butyl 2-methylene-4-(phenylamino)pentanoate (3ma): Compound 3ma
was prepared from (N)-Phenylalanine (1m)[36] following the general
procedure. It was purified by FC (100% Hexane to 95:5 Hexane/EtOAc)
and obtained as a pale-yellow oil (26 mg, 0.10 mmol, 40%): TLC Rf 0.46
(95:5 Hexane/EtOAc); IR ν 3398, 2961, 2929, 2870, 1710, 1602, 1500,
Butyl 4-(benzyloxy)-2-methylenepentanoate (3ia): Compound 3ia was
prepared from (R)-(+)-2-(Benzyloxy)propanoic acid (1i) following the
general procedure. It was purified by FC (100% Hexane to 95:5
Hexane/EtOAc) and obtained as a colorless oil (25 mg, 0.09 mmol, 35%):
TLC Rf 0.40 (95:5 Hexane/EtOAc); IR ν 2968, 2930, 2901, 1715, 1453,
1376, 1125, 1073, 909, 732, 697 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.38
- 7.27 (m, 5H), 6.22 (d, J = 1.7 Hz, 1H), 5.62 (dd, J = 2.6, 1.1 Hz, 1H), 4.53
(q, J = 11.8 Hz, 2H), 4.12 (t, J = 6.6 Hz, 2H), 3.73 (sext, J = 6.1 Hz, 1H),
2.66 (ddd, J = 13.8, 6.8, 0.9 Hz, 1H), 2.43 (ddd, J = 13.8, 6.0, 1.0 Hz, 1H),
1.68 - 1.58 (m, 2H), 1.39 (dq, J = 14.3, 7.3 Hz, 2H), 1.20 (d, J = 6.1 Hz,
3H), 0.94 (t, J = 7.3 Hz, 3H) ppm; 13C-NMR (75 MHz, CDCl3) δ 167.4 (C),
139.0 (C), 137.9 (C), 128.4 (2 × CH), 127.7 (2 × CH), 127.5 (CH2), 127.3
(CH), 73.8 (CH), 70.7 (CH2), 64.7 (CH2), 39.6 (CH2), 30.8 (CH2), 19.8 (CH2),
19.4 (CH2), 13.9 (CH3) ppm; GC RT 13.74 min; HRMS (EI) Calcd. for
C17H24O3 276.1725, found 276.1711.
1
1317, 1255, 1215, 1161, 946, 744, 689 cm-1; H-NMR (300 MHz, CDCl3)
δ 7.19 - 7.12 (m, 2H), 6.69 - 6.60 (m, 3H), 6.22 (d, J = 1.5 Hz, 1H), 5.59
(d, J = 1.3 Hz, 1H), 4.17 (t, J = 6.7 Hz, 2H), 3.71 (h, J = 6.4 Hz, 1H), 2.73
(ddd, J = 13.8, 6.4, 1.0 Hz, 1H), 2.32 (ddd, J = 13.8, 6.9, 0.8 Hz, 1H), 1.71
- 1.62 (m, 2H), 1.47 - 1.34 (m, 2H), 1.18 (d, J = 6.4 Hz, 3H), 0.94 (t, J =
7.3Hz, 3H) ppm; 13C-NMR (101 MHz, CDCl3) δ 167.6 (C), 147.4 (C), 138.3
(C), 129.4 (2 × CH), 127.3 (CH2), 117.2 (CH), 113.3 (2 × CH), 64.9 (CH2),
48.1 (CH), 39.4 (CH2), 30.9 (CH2), 20.7 (CH3), 19.4 (CH2), 13.9 (CH3) ppm;
GC RT = 13.98 min; LRMS (EI) m/z (%) = 261 (M+, 4), 121 (11), 120 (100),
77 (11); HRMS (EI) Calcd. for C16H23NO2 261.1729, found 261.1735.
Butyl 4-((2-methoxyphenyl)amino)-2-methylenebutanoate (3na):
Compound 3na was prepared from (2-Methoxyphenyl)glycine (1n)[22]
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
following the general procedure. It was purified by FC (100% Hexane to
95:5 Hexane/EtOAc) and obtained as a pale-yellow oil (31 mg, 0.11 mmol,
45%): TLC Rf 0.45 (95:5 Hexane/EtOAc); IR ν 2960, 2901, 1713, 1602,
1512, 1244, 1222, 1156, 1124, 1028, 946 cm-1; 1H-NMR (300 MHz, CDCl3)
δ 6.93 - 6.83 (m, 1H), 6.81 - 6.74 (m, 1H), 6.74 - 6.64 (m, 2H), 6.25 (d, J
= 1.3 Hz, 1H), 5.62 (d, J = 1.2 Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H), 3.84 (s,
3H), 3.32 (t, J = 7.0 Hz, 2H), 2.66 (t, J = 6.7 Hz, 2H), 1.75 - 1.60 (m, 2H),
1.42 (dq, J = 14.4, 7.3 Hz, 2H), 0.95 (t, J = 7.3 Hz, 3H) ppm; 13C-NMR (101
MHz, CDCl3) δ 167.2 (C), 147.2 (C), 138.3 (CH2), 137.6 (C), 126.7 (CH),
121.5 (CH), 117.1 (C), 110.5 (CH), 109.7 (CH), 64.9 (CH2), 55.6 (CH3),
43.0 (CH2), 32.0 (CH2), 30.8 (CH2), 19.4 (CH2), 13.9 (CH3) ppm; GC RT
15.0 min; LRMS (EI) m/z (%) = 277 (M+, 16), 136 (100), 121 (14), 120 (17);
HRMS (EI) Calcd. for C16H23NO3 277.1678, found 277.1678.
IR ν 2985, 2976, 2901, 1712, 1599, 1586, 1491, 1406, 1394, 1381, 1241,
1231, 1174, 1157, 1076, 1066, 947, 891, 752, 692 cm-1; 1H-NMR (300 MHz,
CDCl3) δ 7.31 - 7.22 (m, 2H), 6.95 - 6.92 (m, 3H), 6.25 (d, J = 1.5 Hz, 1H),
5.68 (d, J = 1.2 Hz, 1H), 4.61 (h, J = 6.2 Hz, 1H), 4.22 (q, J = 7.1 Hz, 2H),
2.83 (ddd, J = 13.9, 6.5, 0.9 Hz, 1H), 2.50 (ddd, J = 13.9, 6.4, 0.8 Hz, 1H),
1.31 (d, J = 6.2 Hz, 3H), 1.30 (t, J = 7.2 Hz, 3H) ppm; 13C-NMR (101 MHz,
CDCl3) δ 167.2 (C), 158.0 (C), 137.1 (C), 129.6 (2 × CH), 128.0 (CH2),
120.7 (CH), 115.9 (2 × CH), 72.1 (CH), 61.0 (CH2), 39.2 (CH2), 19.8 (CH3),
14.3 (CH3) ppm; GC RT 10.05 min; LRMS (EI) m/z (%) = 234 (M+, 4), 189
(11), 141 (100), 121 (25), 113 (73), 95 (57), 94 (73), 87 (27), 68 (11), 67
(41), 66 (11), 65 (13); HRMS (EI) Calcd. for C14H8O3 234.1256, found
234.162.
Benzyl 2-methylene-4-phenoxypentanoate (3ac): Compound 3ac was
prepared from 2c after 12 h, following the general procedure. It was
purified by FC (100% Hexane to 90:10 Hexane/EtOAc) and obtained as a
pale-yellow oil (47 mg, 0.16 mmol, 65%): TLC Rf 0.47 (95:5
Hexane/EtOAc); IR ν 3014, 1712, 1639, 1591, 1489, 1237, 1214, 1157,
746 cm-1; 1H-NMR (400 MHz, CDCl3) δ 7.40 - 7.32 (m, 5H), 7.25 - 7.19 (m,
2H), 6.95 - 6.84 (m, 3H), 6.31 (d, J = 1.4 Hz, 1H), 5.72 (d, J = 1.2 Hz, 1H),
5.21 (s, 2H), 4.61 (h, J = 6.2 Hz, 1H), 2.85 (ddd, J = 13.9, 6.7, 0.9 Hz, 1H),
2.53 (ddd, J = 13.9, 6.2, 0.8 Hz, 1H), 1.30 (d, J = 6.1 Hz, 3H) ppm; 13C-
NMR (101 MHz, CDCl3) δ 167.0 (C), 158.0 (C), 136.9 (C), 136.0 (C), 129.6
(2 × CH), 128.73 (2 × CH), 128.65 (CH), 128.4 (2 × CH), 128.3 (CH2),
120.7 (CH), 115.9 (2 × CH), 72.0 (CH), 66.8 (CH2), 39.3 (CH2), 19.8 (CH3)
ppm; GC RT 13.28min; LRMS (EI) m/z (%) = 203 (M+ - C6H5O, 19), 94 (11),
91 (100); HRMS (EI) Calcd. for C19H20O3 296.1412, found 296.1406.
Butyl
4-((4-bromophenyl)amino)-2-methylenebutanoate
(3oa):
Compound 3oa was prepared from (4-Bromophenyl)glycine (1o)[22]
following the general procedure. It was purified by FC (100% Hexane to
90:10 Hexane/EtOAc) and obtained as a pale-yellow oil (30 mg, 0.09 mmol,
35%): TLC Rf 0.44 (95:5 Hexane/EtOAc); 1H-NMR (300 MHz, CDCl3) δ
7.27 - 7.21 (m, 2H), 6.53 - 6.48 (m, 2H), 6.24 (d, J = 1.3 Hz, 1H), 5.62 (d,
J = 1.2 Hz, 1H), 4.17 (t, J = 6.6 Hz, 2H), 3.26 (t, J = 6.8 Hz, 2H), 2.61 (td,
J = 6.8, 0.7 Hz, 2H), 1.71 - 1.62 (m, 2H), 1.47 - 1.35 (m, 2H), 0.95 (t, J =
7.3 Hz, 3H) ppm; 13C-NMR (101 MHz, CDCl3) δ 167.2 (C), 146.9 (C), 138.2
(C), 132.1 (2 × CH), 127.0 (CH), 114.7 (2 × CH), 109.2 (C), 65.0 (CH2),
43.2 (CH2), 31.9 (CH2), 30.8 (CH2), 19.4 (CH2), 13.9 (CH3) ppm; GC RT
14.10 min; LRMS (EI) m/z (%) = 327 (M+ 81Br, 13), 325 (M+ 79Br, 14), 186
(95), 185 (11), 184 (100), 105 (11); HRMS (EI) Calcd. for C15H20BrNO2
325.0677, found 325.0650.
Allyl 2-methylene-4-phenoxypentanoate (3ad): Compound 3ad was
prepared from 2d after 12 h, following the general procedure. It was
purified by FC (100% Hexane to 90:10 Hexane/EtOAc) and obtained as a
colorless oil (39 mg, 0.16 mmol, 65%): TLC Rf 0.49 (95:5 Hexane/EtOAc);
IR ν 1720, 1636, 1493, 1211, 1169, 908, 748 cm-1; 1H-NMR (300 MHz,
CDCl3) δ 7.30 - 7.24 (m, 2H), 6.95 - 6.89 (m, 3H), 6.29 (d, J = 1.4 Hz, 1H),
5.95 (ddt, J = 17.2, 10.5, 5.7 Hz, 1H), 5.71 (d, J = 1.2 Hz, 1H), 5.34 (dq, J
= 17.2, 1.5 Hz, 1H), 5.25 (ddd, J = 10.4, 2.6, 1.3 Hz, 1H), 4.67 (dt, J = 5.7,
1.4 Hz, 2H), 4.64 - 4.59 (m, 1H), 2.84 (ddd, J = 13.9, 6.6, 0.9 Hz, 1H), 2.52
(ddd, J = 13.9, 6.2, 0.9 Hz, 1H), 1.31 (d, J = 6.1 Hz, 3H) ppm; 13C-NMR
(101 MHz, CDCl3) δ 166.8 (C), 158.0 (C), 136.9 (C), 132.2 (CH), 129.6 (2
× CH), 128.5 (CH2), 120.8 (CH), 118.4 (CH2), 115.9 (2 × CH), 72.0 (CH),
65.6 (CH2), 39.2 (CH2), 19.8 (CH3) ppm; GC RT 10.45 min; LRMS (EI) m/z
(%) = 246 (M+, 5), 154 (10), 153 (100), 121 (25), 107 (15), 95 (25), 94 (54),
91(10), 67 (30), 65 (10); HRMS (EI) Calcd. for C15H18O3 - C6H5O 153.0916,
found 153.0916.
Butyl 2-methylene-4-(1H-pyrrol)-1-yl)pentanoate (3pa): Compound
3pa was prepared from 2-(1H-Pyrrol-1-yl)propanoic acid (1p)[37] following
the general procedure. It was purified by FC (100% Hexane to 95:5
Hexane/EtOAc) and obtained as a colorless oil (35 mg, 0.15 mmol, 58%):
TLC Rf 0.25 (95:5 Hexane/EtOAc); IR ν 3023, 2955, 2928, 2871, 1707,
1631, 1487, 1220, 1165, 749 cm-1; 1H-NMR (300 MHz, CDCl3) δ 6.67 (t, J
= 2.1 Hz, 2H), 6.11 (t, J = 2.0 Hz, 2H), 6.08 (d, J = 1.4 Hz, 1H), 5.31 (d, J
= 1.2 Hz, 1H), 4.32 (dq, J = 13.4, 6.8 Hz, 1H), 4.16 (t, J = 6.6 Hz, 2H), 2.75
- 2.59 (m, 2H), 1.73 - 1.49 (m, 2H), 1.47 (t, J = 5.3 Hz, 2H), 1.45 - 1.35 (m,
2H), 0.96 (t, J = 7.3 Hz, 3H) ppm; 13C-NMR (75 MHz, CDCl3) δ 170.0 (C),
136.9 (C), 127.8 (CH2), 118.6 (2 × CH), 107.8 (2 × CH), 64.9 (CH2), 54.4
(CH), 41.5 (CH2), 30.8 (CH2), 21.7 (CH3), 19.4 (CH2), 13.9 (CH3) ppm; GC
RT 12.12 min; LRMS (EI) m/z (%) = 235 (M+, 28), 178 (53), 163 (12), 134
(77), 133 (17), 132 (19), 118 (17), 117 (15), 94 (100); HRMS (EI) Calcd.
for C14H21NO2 235.1572, found 235.1568.
Butyl 2-(((3r,5r,7r)-adamantan-1-yl)methyl)acrylate (3qa): It was
prepared from adamantane-1-carboxylic acid (1q, 2 equiv) following the
general procedure, but degasification was performed by three cycles of
freeze-pump-thaw. It was purified by FC (100% Hexane to 95:5
Hexane/EtOAc) and obtained as a colorless oil (27 mg, 0.10 mmol, 40%):
TLC Rf 0.88 (90:10 Hexane/EtOAc); IR ν 2903, 2847, 1718, 1176, 1132,
1059, 806 cm-1; 1H-NMR (300 MHz, CDCl3) 6.19 (d, J = 1.9 Hz, 1H), 5.44
– 5.40 (m, 1H), 4.15 (t, J = 6.7 Hz, 2H), 2.17 (s, 2H), 1.95 (br s, 3H), 1.74
– 1.57 (m, 12H), 1.47 -1.46 (m, 4H), 0.97 (t, J = 7.3 Hz, 3H) ppm; 13C NMR
(101 MHz, CDCl3) δ 168.5 (C), 137.8 (C), 127.0 (CH2), 64.67 (CH2), 45.6
(CH2), 42.2 (3 x CH2), 37.1 (3 x CH2), 33.4 (C), 30.8 (CH2), 28.8 (3 x CH),
19.39 (CH2), 13.88 (CH3) ppm; GC RT 12.33 min; LRMS (EI) m/z (%) =
276 (M+, 1), 203 (2), 136 (11), 135 (100), 79 (10); HRMS (EI) Calcd. for
C18H28O2 276.2089, found 276.2088.
((4-chloropent-4-en-2-yl)oxy)benzene (3ae): Compound 3ae was
prepared from 2e after 12 h, following the general procedure. It was
purified by FC (100% Hexane to 95:5 Hexane/EtOAc) and obtained as a
colorless oil (30 mg, 0.15 mmol, 60%): TLC Rf 0.67 (98:2 Hexane/EtOAc);
IR ν 3025, 2943, 1718, 1635, 1597, 1587, 1494, 1380, 1240, 1220, 1081,
1016, 754 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.32 - 7.25 (m, 2H), 6.97 -
6.90 (m, 3H), 5.25 (s, 2H), 4.70 (h, J = 6.2 Hz, 1H), 2.85 (dd, J = 14.5, 6.3
Hz, 1H), 2.50 (dd, J = 14.4, 6.5 Hz, 1H), 1.35 (d, J = 6.1 Hz, 3H) ppm; 13C-
NMR (75 MHz, CDCl3) δ 157.8 (C), 138.9 (C), 129.7 (2 × CH), 121.1 (CH),
116.2 (2 × CH), 115.0 (CH2), 71.2 (CH2), 46.1 (CH), 19.5 (CH3) ppm; GC
RT 8.18min; LRMS (EI) m/z (%) = 196 (M+, 11), 121 (41), 94 (100), 77 (16);
HRMS (EI) Calcd. for C11H13ClO 196.0655, found 196.0658.
((4-phenoxypent-1-en-2-yl)sulfonyl)benzene (3af): Compound 3af was
prepared from 2f, following the general procedure. In this case the reaction
was run during 40 h employing 2 equiv of 1a and 1 equiv of 2f. It was
purified by FC (100% Hexane to 75:25 Hexane/EtOAc) and obtained as a
white solid (31 mg, 0.10 mmol, 68%): TLC Rf 0.11 (95:5 Hexane/EtOAc);
IR ν 3063, 2980, 2930, 1598, 1586, 1491, 1446, 1304, 1292, 1237, 1173,
Ethyl 2-methylene-4-phenoxypentanoate (3ab): Compound 3ab was
prepared from 2b after 12 h, following the general procedure. It was
purified by FC (100% Hexane to 90:10 Hexane/EtOAc) and obtained as a
colorless oil (45 mg, 0.19 mmol, 76%): TLC Rf 0.54 (98:2 Hexane/EtOAc);
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
1139, 1081, 952, 689 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.92 - 7.82 (m,
2H), 7.65 - 7.57 (m, 1H), 7.55 - 7.45 (m, 2H), 7.30 - 7.20 (m, 2H), 6.98 -
6.88 (m, 1H), 6.84 - 6.76 (m, 2H), 6.44 (br s, 1H), 5.93 (br s, 1H), 4.60 -
4.50 (m, 1H), 2.66 (ddd, J = 15.4, 7.4, 0.8 Hz, 1H), 2.49 (ddd, J = 15.4, 5.2,
1.0 Hz, 1H), 1.26 (d, J = 6.1 Hz, 3H) ppm; 13C-NMR (101 MHz, CDCl3) δ
157.4 (C), 146.7 (C), 138.7 (C), 133.7 (CH), 129.7 (2 × CH), 129.4 (2 ×
CH), 128.3 (2 × CH), 127.0 (CH2), 121.2 (CH), 115.9 (2 × CH), 71.5 (CH),
36.7 (CH2), 19.7 (CH3) ppm; GC RT 16.85 min; LRMS (EI) m/z (%) = 302
(M+, 9), 210 (13), 209 (100), 143 (93), 125 (35), 121 (21), 94 (47), 77 (34),
67 (26), 65 (11); HRMS (EI) Calcd. for C17H18O3S 302.0977, found
302.0985.
Hexane/EtOAc) and obtained as a white solid (38 mg, 0.15 mmol, 60%):
TLC Rf 0.47 (95:5 Hexane/EtOAc); IR ν 2987, 2901, 1597, 1493, 1261,
1217, 1065, 907, 753, 728 cm-1; 1H-NMR (400 MHz, CDCl3) δ 8.02 (d, J =
8.1 Hz, 1H), 7.85 (d, J = 8.0 Hz, 1H), 7.53 - 7.45 (m, 1H), 7.42 - 7.35 (m,
1H), 7.29 - 7.22 (m, 2H), 7.03 - 6.98 (m, 2H), 6.98 - 6.93 (m, 1H), 5.77 (q,
J = 6.5 Hz, 1H), 1.85 (d, J = 6.5 Hz, 3H) ppm; 13C-NMR (101 MHz, CDCl3)
175.1 (C), 157.4 (C), 152.9 (C), 134.9 (C), 129.7 (2 × CH), 126.3 (CH),
125.3 (CH), 123.1 (CH), 122.1 (CH), 121.9 (CH), 115.9 (2 × CH), 74.7 (CH),
23.0 (CH3) ppm; GC RT 14.96 min; LRMS (EI) m/z (%) = 255 (M+, 3), 163
(11), 162 (100), 109 (14); HRMS (EI) Calcd. for C15H13NOS 255.0718,
found 255.0706.
(4-phenoxypent-1-en-2-yl)benzene (3ag): Compound 3ag was prepared
from 2g after 16 h, following the general procedure. It was purified by FC
(100% Hexane to 95:5 Hexane/EtOAc) and obtained as a colorless oil (24
mg, 0.10 mmol, 40%): TLC Rf 0.77 (95:5 Hexane/EtOAc); IR ν 2972, 2949,
2930, 2911, 1598, 1493, 1375, 1231, 1174, 1081, 1067, 1054, 912, 781,
750, 713, 692 cm-1; 1H-NMR (300 MHz, CDCl3) δ 7.45 - 7.16 (m, 7H), 6.94
- 6.85 (m, 1H), 6.84 - 6.74 (m, 2H), 5.33 (d, J = 1.4 Hz, 1H), 5.18 (d, J =
1.1 Hz, 1H), 4.45 - 4.38 (m, 1H), 3.08 (ddd, J = 14.1, 5.8, 0.9 Hz, 1H), 2.65
(ddd, J = 14.1, 7.4, 0.9 Hz, 1H), 1.28 (d, J = 6.1 Hz, 3H) ppm; 13C-NMR
(101 MHz, CDCl3) δ 157.9 (C), 145.3 (C), 141.2 (C), 129.5 (2 × CH), 128.5
(2 × CH), 127.7 (CH), 126.4 (2 × CH), 120.8 (CH), 116.2 (2 × CH), 115.5
(CH), 72.5 (CH), 42.7 (CH2), 19.7 (CH3) ppm; GC RT 11.33 min; LRMS (EI)
m/z (%) = 238 (M+, 25), 146 (12), 145 (100), 144 (30), 143 (18), 130 (17),
129 (84), 128 (21), 121 (54), 117 (21), 115 (18), 103 (33), 94 (17), 91 (22),
77 (34), 65 (10); HRMS (EI) Calcd. for C17H18O 238.1358, found 238.1361.
2-(2,3-dihydrobenzo[b][1,4]dioxin-2-yl)benzo[d]thiazole
(5b):
Compound 5b was prepared from 1,4-Benzodioxane-2-carboxylic acid
(1b) following the general procedure for the decarboxylative arylation. It
was purified by FC (100% Hexane to 95:5 Hexane/EtOAc) and obtained
as
a white solid (43 mg, 0.16 mmol, 64%): TLC Rf 0.31 (95:5
Hexane/EtOAc); IR ν 2987, 2901, 1494, 1263, 1215, 1074, 1053, 907, 748,
729 cm-1; 1H-NMR (400 MHz, CDCl3) δ 8.06 (d, J = 8.2 Hz, 1H), 7.91 (d, J
= 8.0 Hz, 1H), 7.55 - 7.90 (m, 1H), 7.45 - 7.39 (m, 1H), 7.12 - 7.04 (m, 1H),
6.99 - 6.89 (m, 3H), 5.65 (dd, J = 6.9, 2.7 Hz, 1H), 4.72 (dd, J = 11.4, 2.7
Hz, 1H), 4.43 (dd, J = 11.4, 6.9 Hz, 1H) ppm; 13C-NMR (101 MHz, CDCl3)
δ 167.8 (C), 153.1 (C), 143.2 (C), 142.4 (C), 135.0 (C), 126.5 (CH), 125.6
(CH), 123.4 (CH), 122.4 (CH), 122.2 (CH), 122.0 (CH), 117.7 (CH), 117.6
(CH), 73.6 (CH), 67.2 (CH2) ppm; GC RT 16.66 min; LRMS (EI) m/z (%) =
270 (M+ + 1, 11), 269 (63), 241 (11), 226 (11), 224 (36), 207 (11), 162 (12),
161 (100), 160 (37), 135 (26), 108 (12), 69 (11). Characterization data
matched that reported in the literature.[39]
2-methylene-3-phenethyl-4-phenoxypentanenitrile (3ah): Compound
2ah was prepared from 2h after 48 h, following the general procedure. In
this case 2 equiv of 1a and 1 equiv of 2h were used. It was purified by FC
(100% Hexane to 95:5 Hexane/EtOAc) and obtained as a colorless oil (26
mg, 0.09 mmol, 32% in a 3:2 dr according to GC): TLC Rf 0.30 (95:5
Hexane/EtOAc); IR ν 2950, 2925, 2166, 2036, 1598, 1492, 1238, 1078,
944, 752, 694 cm-1; 1H-NMR (300 MHz, CDCl3) (mixture of
diastereoisomers) δ 7.35 - 7.13 (m, 9H), 7.00 - 6.84 (m, 3H), 6.10 (d, J =
0.6 Hz, 0.47H), 6.08 (d, J = 0.5 Hz, 0.44 H), 5.84 (brs, 0.47H), 5.82 (brs,
0.47H), 4.45 - 4.33 (m, 1H), 2.84 - 2.68 (m, 1H), 2.61 - 2.36 (m, 2H), 2.28
– 2.12 (m, 1H), 2.08 - 1.80 (m, 2H), 1.30 (d, J = 0.7 Hz, 1.5H), 1.28 (d, J =
0.6 Hz, 1.5H) ppm; 13C-NMR (101 MHz, CDCl3) (mixture of
diastereoisomers) δ 157.7, 157.6, 141.08, 141.05, 133.9, 133.7, 129.8,
129.7, 128.67, 128.65, 128.5, 126.3, 126.28, 121.4, 121.3, 116.3, 116.0,
75.1, 75.0, 50.31, 50.26, 33.31, 33.3, 30.9, 17.5, 17.4 ppm; GC
Diastereoisomer A: RT 15.90 min; Diastereoisomer B: RT 16.00 min; LRMS
(EI) Diastereoisomer A: m/z (%) = 291 (M+, 15), 121 (83), 105 (15), 94 (68),
92 (11), 91 (100), 77 (25), 65 (13); Diastereoisomer B: m/z (%) = 291 (M+,
14), 121 (81), 105 (16), 94 (73), 91 (100), 77 (23), 65 (14); HRMS (EI)
Calcd. for C20H21NO 291.1623, found 291.1623.
2-((2-methoxyphenoxy)methyl)benzo[d]thiazole (5c): Compound 5c
was prepared from 2-(2-Methoxyphenoxy)acetic acid (1g) following the
general procedure for the decarboxylative arylation. It was purified by FC
(100% Hexane to 85:15 Hexane/EtOAc) and obtained as a yellow oil (41
mg, 0.15 mmol, 60%): TLC Rf 0.16 (95:5 Hexane/EtOAc); IR ν 2971, 2901,
1
1501, 1254, 1045, 1028, 905, 760, 724 cm-1; H-NMR (300 MHz, CDCl3)
δ 8.03 (d, J = 8.0 Hz, 1H), 7.89 (d, J = 8.6 Hz, 1H), 7.53 - 7.45 (m, 1H),
7.44 - 7.36 (m, 1H), 7.06 - 7.00 (m, 1H), 6.98 - 6.92 (m, 2H), 6.91 - 6.83
(m, 1H), 5.56 (s, 2H), 3.92 (s, 3H) ppm; 13C-NMR (101 MHz, CDCl3) δ
150.1 (C), 147.4 (C), 126.6 (C), 125.7 (C), 123.2 (CH), 122.9 (CH), 122.1
(CH), 121.1 (2 × CH), 115.6 (C), 112.5 (2 × CH), 69.3 (CH2), 56.2 (CH3)
ppm; GC RT 16.44 min; LRMS (EI) m/z (%) = 271 (M+, 22), 149 (13), 148
(100); HRMS (EI) Calcd. for C15H13NO2S 271.0667, found 271.0667.
2-(1-(benzyloxy)ethyl)benzo[d]thiazole (5d): Compound 5d was
prepared from (R)-(+)-2-(Benzyloxy)propanoic acid (1i) following the
general procedure for the decarboxylative arylation. It was purified by FC
(100% Hexane to 90:10 Hexane/EtOAc) and obtained as a pale-yellow oil
(27 mg, 0.10 mmol, 40%): TLC Rf 0.31 (95:5 Hexane/EtOAc); IR ν 2987,
2901, 1508, 1395, 1215, 1066, 1056, 907, 747, 725 cm-1; 1H-NMR (300
MHz, CDCl3) δ 8.03 (dd, J = 8.1, 0.5 Hz, 1H), 7.92 (dd, J = 7.9, 0.7 Hz,
1H), 7.54 - 7.28 (m, 8H), 5.01 (q, J = 6.5 Hz, 1H), 4.69 (d, J = 11.6 Hz, 1H),
4.60 (d, J = 11.6 Hz, 1H), 1.70 (d, J = 6.5 Hz, 3H) ppm; 13C-NMR (101
MHz, CDCl3) δ 176.5 (C), 152.8 (C), 137.6 (C), 134.9 (C), 128.6 (2 × CH),
128.1 (2 × CH), 128.0 (2 × CH), 126.2 (CH), 125.3 (CH), 123.0 (CH), 122.1
(CH), 75.7 (CH), 71.8 (CH2), 22.7 (CH3) ppm; GC RT 15.58 min; LRMS
(EI) m/z (%) = 224 (10), 164 (12), 163 (100), 162 (M+- OBn, 46), 91 (33);
HRMS (EI) Calcd. for C9H9NS 163.0456, found 163.0451.
General procedure for the decarboxylative arylation of carboxylic
acids: 2-(phenylsulfonyl)benzo[d]thiazole (4, 68.8 mg, 0.25 mmol, 1 equiv)
was added to a 2 dram vial equipped with a stirring magnetic bar, followed
by RFTA (13.6 mg, 0.025 mmol, 10 mol-%), the corresponding carboxylic
acid (0.50 mmol, 2 equiv) and MeCN (2.5 mL). The vial was sealed with a
septum and the reaction mixture submitted to three cycles of freeze-pump-
thaw. Finally, the vial was equipped with an Ar balloon and the yellow
mixture[38] was stirred at 25 ºC under blue LEDs irradiation (λ = 455 nm,
15 ± 2 mW/cm2)[34] until no progress was observed by TLC or GC
(generally 36 h). The solvent was removed under reduced pressure,
affording a residue which was purified by FC.
2-((3aR,6R,6aR)-6-methoxy-2,2-dimethyltetrahydrofuro[3,4
d][1,3]dioxol-4-yl)benzo[d]thiazole (5e): Compound 5e was prepared
from 2,3-O-isopropylidene-1-O-methyl-D-ribosic acid (1h) following the
general procedure for the decarboxylative arylation. It was purified by FC
(100% Hexane to 90:10 Hexane/EtOAc) and obtained as a colorless oil
(28 mg, 0.09 mmol, 35%): TLC Rf 0.23 (95:5 Hexane/EtOAc); IR ν 2986,
2-(1-phenoxyethyl)benzo[d]thiazole (5a): Compound 5a was prepared
from 2-Phenoxypropanoic acid (1a) following the general procedure for the
decarboxylative arylation. It was purified by FC (100% Hexane to 90:10
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
2934, 1598, 1493, 1446, 1375, 1306, 1239, 1141, 1084, 907, 867, 728,
689 cm-1; 1H-NMR (300 MHz, CDCl3) δ 8.02 (d, J = 8.2 Hz, 1H), 7.88 (dd,
J = 7.9, 0.7 Hz, 1H), 7.52 - 7.44 (m, 1H), 7.43 - 7.35 (m, 1H), 5.60 (dd, J =
5.9, 1.1 Hz, 1H), 5.54 (br s, 1H), 5.17 (s, 1H), 4.69 (d, J = 5.9 Hz, 1H), 3.39
(s, 3H), 1.57 (s, 3H), 1.57 (s, 3H) ppm; 13C-NMR (75 MHz, CDCl3) δ 170.2
(C), 152.9 (C), 135.4 (C), 126.3 (CH), 125.4 (CH), 123.3 (CH), 121.8 (CH),
113.1 (C), 111.1 (CH), 86.4 (CH), 85.4 (CH), 84.2 (CH), 56.2 (CH3), 26.7
(CH3), 25.3 (CH3) ppm; GC RT 15.48 min; LRMS (EI) m/z (%) = 292 (M+ -
CH3, 10), 218 (11), 208 (11), 207 (92), 190 (25), 189 (23), 165 (14), 164
(39), 163 (30), 162 (17), 161 (100), 160 (22), 135 (25), 108 (12), 85 (15),
58 (14); HRMS (EI) Calcd. for C15H17NO4S 307.0878, found 307.0883.
NMR (300 MHz, CDCl3) δ 6.15 (d, J = 1.4 Hz, 1H), 5.54 (dd, J = 2.7, 1.3
Hz, 1H), 4.16 (t, J = 6.6 Hz, 2H), 4.07 (p, J = 6.5 Hz, 1H), 3.93 (td, J = 8.4,
3.7 Hz, 1H), 3.69 (dd, J = 15.6, 8.3 Hz, 1H), 2.45 - 2.20 (m, 2H), 2.19 -
1.95 (m, 2H), 1.75 - 1.57 (m, 5H), 1.47 - 1.36 (m, 2H), 1.08 (d, J = 6.5 Hz,
3H), 0.95 (t, J = 7.3 Hz, 3H) ppm; 13C-NMR (101 MHz, CDCl3) δ 167.4,
141.0, 124.7, 66.5, 64.7, 41.8, 31.11, 31.08, 30.8, 28.9, 19.4, 16.2, 13.9
ppm; GC RT 12.61 min; LRMS (EI) m/z (%) = 167 (M+, 25), 166 (84), 151
(48), 140 (18), 139 (10), 138 (20), 125 (20), 124 (16), 123 (39), 122 (20),
121 (26), 112 (16), 111 (54), 110 (17), 109 (11), 108 (11), 107 (11), 105
(10), 99 (11), 98 (28), 97 (66), 96 (25), 95 (100), 94 (40), 93 (30); HRMS
(EI) Calcd. for C14H24O3 – C4H10O2 166.0994, found 166.099.
N-(benzo[d]thiazol-2-ylmethyl)aniline (5f): Compound 5f was prepared
from (N)-Phenylglycine (1l) following the general procedure for the
decarboxylative arylation. It was purified by FC (100% Hexane to 80:20
Butyl
2-((2,3-dihydrobenzo[b][1,4]dioxin-2-yl)methyl)-4-(p-
tolyloxy)butanoate (6): Compound 1d (57 mg, 0.3 mmol, 1.5 equiv.) was
added to a 2 dram vial equipped with a stirring magnetic bar, followed by
a solution of 3ba (49.8 mg, 0.2 mmol, 1 equiv.) in MeCN (0.7 mL), Na2CO3
(4.24 mg, 0.04 mmol, 20 mol-%) and [Mes-Acr]ClO4 (2.08 mg, 2.5 mol-%).
Finally, H2O (0.3 mL) was added and the vial was sealed with a cap. The
yellow solution was irradiated using blue LED’s and stirred at room
temperature, without any inert atmosphere, until complete conversion was
observed (monitored by TLC and/or GC, 22 h). The reaction mixture was
concentrated under reduced pressure and the residue was purified by FC
(100% Hexane to 90:10 Hexane/EtOAc) to obtain 6 as a colorless oil (36
mg, 0.09 mmol, 45%): (~2:1 dr according to GC-MS); TLC Rf 0.47(90:10
Hexane/EtOAc); IR ν 2965, 2926, 1729, 1510, 1494, 1264, 1241, 1175,
1045, 817, 746 cm-1; 1H-NMR (400 MHz, CDCl3) (mixture of
diastereoisomers) δ 7.07 (d, J = 8.2 Hz, 2H), 6.85 - 6.82 (m, 4H), 6.78 -
6.76 (m, 2H), 4.25 - 3.87 (m, 6H), 3.11 - 2.85 (m, 1H), 2.28 (s, 3H), 2.21 -
1.93 (m, 2H), 1.88 - 1.74 (m, 1H), 1.60 - 1.55 (m, 2H), 1.41 - 1.30 (m, 2H),
0.94 – 0.77 (m, 3H) ppm; 13C-NMR (101 MHz, CDCl3) (mixture of
diastereoisomers) δ 175.3, 156.7, 143.24, 143.15, 143.12, 130.20, 130.19,
130.0, 121.7, 121.6, 121.48, 117.52, 117.51, 117.2, 114.53, 114.50, 71.3,
68.1, 67.8, 65.7, 65.6, 64.84, 64.81, 39.0, 38.6, 33.4, 33.2, 32.5, 31.7, 30.7,
20.6, 19.29, 19.28, 13.83,13.80 ppm; GC RT Diastereoisomer A: 24.07
min; Diastereoisomer B: 24.50 min LRMS (EI) m/z (%) = Diastereoisomer
A: 398 (M+, 10), 325 (13), 291 (30), 236 (15), 235 (100), 149 (12), 147 (10),
135 (26), 125 (10), 121 (17), 108 (10), 107 (11), 101 (10); Diastereoisomer
B: 398 (M+, 11), 325 (13), 291 (27), 236 (14), 235 (100), 149 (11), 135 (22),
121 (15); HRMS (EI) Calcd. for C24H30O5 398.2093, found 398.2081.
i
Hexane/EtOAc) and then treated with PrOH/Hexanes to filtered out the
starting sulfone and obtain 5f as a colorless oil (36 mg, 0.15 mmol, 60%):
TLC Rf 0.13 (95:5 Hexane/EtOAc); IR ν 2987, 2901, 1216, 1066, 1056,
906, 754, 727, 671 cm-1; 1H-NMR (300 MHz, CDCl3) δ 8.01 (d, J = 7.9 Hz,
1H), 7.83 (dd, J = 8.0, 0.6 Hz, 1H), 7.51 - 7.45 (m, 1H), 7.39 - 7.34 (m, 1H),
7.23 - 7.15 (m, 2H), 6.84 - 6.67 (m, 3H), 4.78 (s, 2H) ppm; 13C-NMR (101
MHz, CDCl3) δ 173.2 (C), 153.6 (C), 147.0 (C), 129.5 (2 × CH), 126.1 (CH),
125.0 (CH), 122.9 (CH), 121.9 (CH), 118.9 (C), 113.4 (2 × CH), 47.2 (CH2)
ppm; GC RT 16.29 min; LRMS (EI) m/z (%) = 241 (M+ + 1, 18), 240 (100),
239 (27), 238 (24), 237 (27), 210 (13), 149 (10), 148 (36), 136 (23), 135
(11), 108 (10), 106 (76), 105 (13), 104 (12), 77 (30); HRMS (EI) Calcd. for
C14H12N2S 240.0721, found 240.0718.
General procedure for the synthesis of 3qa and 7: 2-(but-3-en-1-
yloxy)propanoic acid[40] (1q) (28.8 mg, 0.2 mmol, 1 equiv) was added to a
2 dram vial equipped with a stirring magnetic bar, followed by RFTA (5.44
mg, 0.01 mmol, 5 mol-%), and a solution of 2a (0.22 mmol, 56.4 mg, 1.1
equiv) in MeCN (4 mL). The vial was sealed with a septum and the reaction
mixture submitted to three cycles of freeze-pump-thaw. Finally, the vial
was equipped with an Ar balloon and the yellow mixture was stirred at 25
ºC under blue LEDs irradiation (λ = 455 nm, 15 ± 2 mW/cm2) until no
progress was observed by TLC or GC (24 h). The solvent was removed
under reduced pressure and pure compounds 3qa and 7 was obtained
after purification by flash column chromatography.
Butyl 4-(but-3-en-1-yloxy)-2-methylenepentanoate (3qa): Compound
3qa was prepared from 2-(but-3-en-1-yloxy)propanoic acid (1q) following
the procedure above described. It was purified by FC (100% Hexane to
90:10 Hexane/EtOAc) and obtained as a colorless oil (15 mg, 0.06 mmol,
30%): TLC Rf 0.75 (90:10 Hexane/EtOAc); IR ν 2960, 2930, 2873, 1716,
1631, 1458, 1326, 1219, 1125, 912, 735 cm-1; 1H-NMR (300 MHz, CDCl3)
δ 6.19 (d, J = 1.7 Hz, 1H), 5.81 (ddt, J = 17.0, 10.2, 6.7 Hz, 1H), 5.60 (dd,
J = 2.7, 1.1 Hz, 1H), 5.12 - 4.97 (m, 2H), 4.15 (t, J = 6.6 Hz, 2H), 3.64 -
3.39 (m, 3H), 2.59 (ddd, J = 13.8, 6.7, 1.0 Hz, 1H), 2.35 (ddd, J = 13.8, 6.7,
1.0 Hz, 1H), 2.32 -2.25 (m, 2H), 1.72 – 1.59 (m, 2H), 1.50 – 1.35 (m, 2H),
1.14 (d, J = 6.2 Hz, 3H), 0.95 (t, J = 7.3 Hz, 3H) ppm; 13C-NMR (101 MHz,
CDCl3) δ 167.5 (C), 137.9 (C), 135.6 (CH), 127.2 (CH2), 116.3 (CH2), 74.3
(CH), 68.2 (CH2), 64.7 (CH2), 39.4 (CH2), 34.7 (CH2), 30.8 (CH2), 19.8
(CH2), 19.4 (CH3), 13.9 (CH3) ppm; GC RT 11.23 min; LRMS (EI) m/z (%)
= 155 (M+ - C5H9O, 11), 113 (45), 111 (11), 99 (54), 95 (18), 81 (31), 69
(18), 67 (14), 55 (100); HRMS (EI) Calcd. for C14H24O3 – C9H5O2 155.1072,
found 155.1066.
Acknowledgments
This work was generously supported by the Spanish Ministerio de
Economía y Competitividad (CTQ2017-88171-P) and the Generalitat
Valenciana (AICO/2017/007). N. P. R. thanks to Instituto de Síntesis
Orgánica for financial support.
Keywords: allylation • carboxylic acids • photocatalysis • radicals
• sustainable chemistry
[1]
For recent reviews, see: a) N. A. Romero, D. A. Nicewicz, Chem. Rev.,
2016, 116, 10075-10166; b) D. Staveness, I. Bosque; C. R. J.
Stephenson, Acc. Chem. Res., 2016, 49, 2295–2306; c) J. K. Matsui, S.
B. Lang, D. R. Heitz, G. A. Molander, ACS Catal. 2017, 7, 2563−2575;
d) L. M. Marzo, S. K. Pagire, O. Reiser, B. König, Angew. Chem. Int. Ed.
2018, 57, 10034–10072; e) C. R. J. Stephenson, T. P. Yoon, D. W. C.
Macmillan, Visible Light Photocatalysis in Organic Chemistry; Wiley:
Weinheim, Germany, 2018.
Butyl
2-methylene-4-[(2R,3S)-2-methyltetrahydrofuran-3-
was prepared from 2-(but-3-en-1-
yl)butanoate (7): Compound
7
yloxy)propanoic (1q) following the procedure above described. It was
purified by FC (100% Hexane to 90:10 Hexane/EtOAc) and obtained as a
colorless oil (10 mg, 0.04 mmol, 21%): TLC Rf 0.44 (90:10 Hexane/EtOAc);
IR ν 2959, 2929, 2872, 1718, 1457, 1186, 1155, 1069, 941, 735 cm-1; 1H-
[2]
J. K. Kochi, T. M. Bockman, S. M. Hubig, J. Org. Chem. 1997, 62, 2210-
2221.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
[3]
Potassium alkyltrifluoroborates have relatively low oxidation potentials
and have been employed as radical precursors in many photocatalyst-
mediated transformations. For some relevant examples, see: a) Y. Yasu,
T. Koike, M. Akita, Adv. Synth. Catal. 2012, 354, 3414-3420; b) K.
Miyazawa, Y. Yasu, T. Koike, M. Akita, Chem. Commun. 2013, 49, 7249-
7251; c) J. C. Tellis, D. N. Primer, G. A. Molander, Science 2014, 345,
433-436; d) G. A. Molander, J. Org. Chem. 2015, 80, 7837-7848; e) D.
N. Primer, I. Karakaya, J. C. Tellis, G. A. Molander, J. Am. Chem. Soc.
2015, 137, 2195-2198.
[22] Y. Duan, M. Zhang, R. Ruzi, Z. Wu, C. Zhu, Org. Chem. Front., 2017, 4,
525-528. This photocatalyst can be purchased from Strem Chemicals
(Product number: 77-0465) at ≈ 582€/ mmol. The reaction is limited to
N-arylglycine most likely due to the poor oxidation power of this
photocatalyst [E1/2 (*IrIII/IrII) = +0.81 V vs SCE].
[23] RFTA was obtained in one step by acetylation of RF, according to a
reported procedure: R. A. Larson, P.L. Stackhouse, T.O. Crowley,
Environ. Sci. Technol. 1992, 26, 1792-1798.
[24] C. K. Remucal, K. McNeill, Environ. Sci. Technol. 2011, 45, 5230–5237.
[25] It is reported that electron transfer between 3RFTA* and its ground state
can generate the corresponding oxidized and reduced radicals (D-D
reaction); see: P. F. Heelis, Chem. Soc. Rev. 1982, 11, 15-39. We
acknowledge to one of the reviewers for this suggestion. The [RFTA]•- is
also regenerated after the PET between the 3RFTA* and the carboxylate.
[26] a) For the pKa value of RFlH/RFl-, see: A. Enrenberg, F. Müller, P.
Hemmerich, Eur. J. Biochem., 1967, 2, 286-293; b) For a recent
characterization of RFTA where deprotonation of carboxylic acids is
proposed by the corresponding radical anion, see: M. März, M. Kohout,
T. Neveselý, J. Chudoba, D. Prukata, S. Nizinski, M. Sikorski, G.
Burdzinski, R. Cibulka, Org. Biomol. Chem., 2018, 16, 6809-6817.
[27] B. Persson, Acta Chem. Scand. 1977, 31B, 88-89.
[4]
Light-mediated oxidation of alkyl bis(catecholato)-silicates can be carried
out using mildly oxidizing photocatalysts to generate alkyl radicals (E1/2
= +0.3 to +0.9 V vs. SCE). For relevant references, see: a) D. Matsuoka,
Y. Nishigaichi, Chem. Lett. 2015, 44, 163−165; b) V. Corcé, L. M.
Chamoreau, E. Derat, J.-P. Goddard, C. Ollivier, L. Fensterbank, Angew.
Chem., Int. Ed. 2015, 54, 11414−11418; c) K. Lin, C. B. Kelly, M. Jouffroy,
G. A. Molander, Org. Synth. 2017, 94, 16-33.
[5]
[6]
DHPs might undergo photocatalyst-mediated oxidative fragmentation
(E1/2 = +1.10 V vs. SCE), generating alkyl radicals and pyridinium salts.
See: J.-P. Cheng, Y. Lu, X.-Q. Zhu, Y. Sun, F. Bi, J. He, J. Org. Chem.
2000, 65, 3853−3857.
Single-electron reduction of Katritzky pyridinium salts (E1/2 = −0.93 V vs.
SCE) has recently been employed for the generation of alkyl radicals.
See: F. J. R. Klauck, M. J. James, F. Glorius, Angew. Chem., Int. Ed.,
2017, 56, 12336-12339.
[28] Values from –0.80 V to –0.45 V have been reported, to be dependent on
the solvents. See: R. Martinez-Haya, M. A. Miranda, M. L. Marin, Eur. J.
Org. Chem. 2017, 2164–2169, and references therein.
[7]
[8]
[9]
For recent reviews, see: a) A. J. J. Straathof, Chem. Rev. 2014, 114,
1871-1908; b) H. Fu, Y. Jin, Asian J. Org. Chem. 2017, 6, 368 - 385.
L. Capaldo, L. Buzzetti, D. Merli, M. Fagnoni, D. Ravelli, J. Org. Chem.
2016, 81, 7102−7109.
[29] The radical generated is stabilized by orbital interactions with both axial
ring oxygen lone pair and adjacent * C-O bond (anomeric effect), and
reacts from the less hindered convex face. For precedents, see: a) S.
Ventre, F. R. Petronijevic, D. W. C. MacMillan, J. Am. Chem. Soc. 2015,
137, 5654−5657; b) X. Zhou, P. Wang, L. Zhang, P. Chen, M. Ma, N.
Song, S. Ren, M. Li, J. Org. Chem. 2018, 83, 588−603.
For some relevant examples, see: a) D. S. Hamilton, D. A. Nicewicz, J.
Am. Chem. Soc. 2012, 134, 18577−18580; b) A. J. Perkowski, D. A.
Nicewicz, J. Am. Chem. Soc. 2013, 135, 10334−10337; c) M. A. Zeller,
M. Riener, D. A. Nicewicz, Org. Lett. 2014, 16, 4810−4813.
[30] Since the reaction mixture is homogeneous during all the process, a
possible solution to scale up the reaction would be to use a flow reactor,
where the illuminated area-to-reaction volume ratio is maximized. For
some recent examples, see: a) J. W. Beatty, J. J. Douglas, R. Miller, R.
C. McAtee, K. P. Cole, C. R. J. Stephenson, Chem. 2016, 1, 456–472;
b) H. Seo, M. H. Katcher, T. F. Jamison, Nat. Chem. 2017, 9, 453-456;
c) F. Lima, L. Grunenberg, H. B. A. Rahman, R. Labes, J. Sedelmeierb,
S. V. Ley, Chem. Commun., 2018, 54, 5606-5609; d) J. C. Gonzalez-
Gomez, N. P. Ramirez, T. Lana-Villarreal, P. Bonete, Org. Biomol. Chem.
2017, 15, 9680-9684.
[10] a) D. Hanss, J. C. Freys, G. Bernardinelli, O. S. Wenger, Eur. J. Inorg.
Chem. 2009, 4850-4859; b)This photocatalyst can be purchased from
Sigma-Aldrich (Product number: 804215) at ≈ 1360 €/ mmol.
[11] Riboflavin can be purchased from TCI-Europe (Product number: R0020)
at ≈ 0.27 €/ mmol.
[12] K. S. Conrad, C. C. Manahan, B. R. Crane, Nat. Chem. Bio. 2014, 10,
801-809.
[13] a) For photophysical properties of riboflavin, see: B. König, S. Kümmel,
R. Cibulka, Flavin photocatalysis. In Chemical Photocatalysis: B. König,
Ed. De Gruyter: Regensburg, 2013, p 45-66, and references therein; b)
For standard redox potentials of carboxylic acids, see: H. G. Roth, N. A.
Romero, D. A. Nicewicz, Synlett 2016, 27, 714−723.
[31] N. P. Ramirez, J. C. Gonzalez-Gomez, Eur. J. Org. Chem. 2017, 2154-
2163.
[32] Details can be found in the supporting information file. For
a
comprehensive discussion of this issue, see: M. A. Cismesia, T. P. Yoon,
Chem. Sci. 2015, 6, 5426-5434.
[14] a) J. B. Metternich, R. Gilmour, J. Am. Chem. Soc. 2016, 138,
1040−1045; b) T. Morack, J. B. Metternich, R. Gilmour, Org. Lett. 2018,
20, 1316-1319.
[33] For a recent photocatalytic procedure for the decarboxylative C2-
alkylation of benzothiazoles with carboxylic acids, see: B. Wang, P. Li, T.
Miao, L. Zou, L. Wang, Org. Biomol. Chem. 2019, 17, 115-122.
[34] The incident light intensity on the reactor was measured using an optical
power meter (Thorlabs PM100D) equipped with a thermopile sensor
(Thorlabs model S310C).
[15] S. Bloom, C. Liu, D. K. Kölmel, J. X. Qiao, Y. Zhang, M. A. Poss, W. R.
Ewing, D. W. C. MacMillan, Nat. Chem. 2018, 10, 205-211.
[16] N. P. Ramirez, B. König, J. C. Gonzalez-Gomez, Org. Lett, 2019, 21,
1368-1373.
[17] a) G. A. Russell, P. Ngoviwatchai, H. Tashtoush, A. Pla-Dalmau, R. K.
Khanna, J. Am. Chem. Soc. 1988, 110, 3530-3538; b) Y. Amaoka, M.
Nagatomo, M. Watanabe, K. Tao, S. Kamijo, M. Inoue, Chem. Sci. 2014,
5, 4339-4345; c) A. Noble, D. W. C. MacMillan, J. Am. Chem. Soc. 2014,
136, 11602-11605; d) Reference 4b.
[35] Prepared according: E. J. Corey, S. Barcza, G. Klotmann, J. Am. Chem.
Soc. 1969, 91, 4782 - 4786.
[36] Prepared according to: Sharma, K. K.; Sharma, S.; Kudwal, A.; Jain, R.
Org. Biomol. Chem. 2015, 13, 4637 – 4641.
[37] N. N. Bhuvan Kumar, O. A. Mukhina, A. G. Kutateladze, J. Am. Chem.
Soc. 2013, 135, 9608 – 9611.
[18] For precedents in the radical addition to 2-(phenylsulfonyl)benzothiazole,
see: a) D. B. Jacobson, B. S. Freiser, J. Am. Chem. Soc. 1984, 106,
4623-4624; b) Y. Ikeda, R. Ueno, Y. Akai, E. Shirakawa, Chem.Commun.,
2018, 54, 10471-10474.
[38] The aryl sulfone was only dissolved after few minutes of irradiation.
[39] W. - M. Zao, X. -L. Chen, J. - W. Yuan, L. - B. Qu, L. - K. Duan, Y. - F.
Zhao, Chem. Commun. 2014, 50, 2018 - 2020.
[19] For a recent review: A. Rouf, C. Tanyeli, Eur. J. Med. Chem. 2015, 97,
911-927.
[40] M. Eh, Synthesis 2003, 3, 365 - 370.
[20] C. Hu, Y. Chen, Org. Chem. Front., 2015, 2, 1352-1355.
[21] L. Cui, H. Chen, C. Liu, C. Li, Org. Lett., 2016, 18, 2188-2191.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900888
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
FULL PAPER
The direct decarboxylative allylation of
carboxylic acids with allylsulfones can
be efficiently promoted at room
temperature by visible light using
inexpensive RFTA as photocatalyst in
the absence of base. Under similar
conditions, some carboxylic acids can
Synthetic Methods*
Nieves P. Ramirez, Teresa Lana-
Villarreal, Jose C. Gonzalez-Gomez
Page No. – Page No.
Direct decarboxylative allylation and
arylation of aliphatic carboxylic acids
using flavin mediated photoredox
catalysis
be
decarboxylative homolytic aromatic
substitution of 2-
successfully
used
in
the
(phenylsulfonyl)benzothiazole.
*Riboflavin photocatalysis
This article is protected by copyright. All rights reserved.