Photochemical addition of cyclic ethers/acetals to olefins using tBuOOtBu: Synthesis of masked ketones/aldehydes and diols

Article abstract of DOI:10.1016/j.tet.2020.131557

A fast photochemical C–C bond formation between cyclic ethers/acetals and olefins using di-tert-butyl peroxide (DTBP) was developed. This method provides easy access to 2-substituted cyclic ethers, and 2- or 4-substituted cyclic acetals. Acyl/formyl groups or diols can be obtained by the hydrolysis of the 2- or 4-substituted cyclic acetals, respectively. The reactions proceeded at room temperature and gave the expected products in good to excellent yields; efficient reactions were completed within 0.5 h at room temperature in >95% yield.

Full text of DOI:10.1016/j.tet.2020.131557

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Photochemical addition of cyclic ethers/acetals to olefins using
tBuOOtBu: Synthesis of masked ketones/aldehydes and diols
Mamiko Hayakawa a, Rina Shimizu a, Hajime Omori a, Hisashi Shirota a, Kou Uchida a,
Hiroshi Mashimo a, Han Xu a, Ryuusei Yamada a, Seiya Niino a, Yoshiki Wakame a,
,
, *
Chuanxiang Liu b 1, Tadashi Aoyama a, Akihiko Ouchi a
a Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8308,
Japan
b National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8565, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A fast photochemical CeC bond formation between cyclic ethers/acetals and olefins using di-tert-butyl
peroxide (DTBP) was developed. This method provides easy access to 2-substituted cyclic ethers, and 2-
or 4-substituted cyclic acetals. Acyl/formyl groups or diols can be obtained by the hydrolysis of the 2- or
4-substituted cyclic acetals, respectively. The reactions proceeded at room temperature and gave the
expected products in good to excellent yields; efficient reactions were completed within 0.5 h at room
temperature in >95% yield.
Received 5 August 2020
Received in revised form
22 August 2020
Accepted 27 August 2020
Available online xxx
© 2020 Elsevier Ltd. All rights reserved.
Keywords:
Photochemical reaction
CeC bond formation
Radical
Ether
Acetal
Olefin
1. Introduction
particular, the addition of cyclic ethers and acetals to C]C bonds
(Scheme 1) is of synthetic importance because the introduction of
CeC bond formation is one of the most important reactions in
organic synthesis and has been extensively and intensively studied.
In contrast to ionic reactions, radical reactions are less studied
probably due to the necessity of severe conditions, such as high
temperature, for the generation of radicals, which often induce
undesirable side reactions. However, many functional groups that
need protection under ionic reaction conditions are tolerated in
radical reactions, which is a significant advantage toward the syn-
thesis of organic compounds. Therefore, the development of simple
and efficient radical reactions for the construction of new CeC
bonds is still a challenge in synthetic chemistry. The addition of
carbon radicals to olefins is one of the fundamental radical CeC
bond forming reactions that has been widely studied [1]. In
side chains at the carbon next to oxygen in cyclic ethers (Scheme
1a) can be used toward the synthesis of various bioactive natural
compounds [2] and acetals can be used as synthons for ketones and
aldehydes (Scheme 1b), and for diols (Scheme 1c). Thus, the re-
actions shown in Scheme 1b and c imply that the reaction involves
not only CeC bond formation but also the introduction of syn-
thetically useful functional groups.
For the generation of carbon radicals, C-heteroatom and CeH
bond cleavage reactions have been widely used, in which the
latter has advantage over the former because it needs additional
reactions to introduce the requisite C-heteroatom bond, which
often require toxic reagents and harsh conditions [1]. Indeed, CeC
bond formation using the direct activation of CeH bonds is now
considered as one of the most challenging reactions. Conventional
studies on the generation of carbon radicals via the abstraction of
the hydrogen atom of a CeH bond can be briefly classified into
three types: (i) Thermal reactions using radical initiators, (ii)
photochemical reactions using ketones, and (iii) reactions using
photoredox catalysts.
* Corresponding author.
E-mail address: ouchi.akihiko@nihon-u.ac.jp (A. Ouchi).
Present address: Pharmaceutical Engineering Group, School of Chemical and
1
Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Rd,
Shanghai 201418, China.
https://doi.org/10.1016/j.tet.2020.131557
0040-4020/© 2020 Elsevier Ltd. All rights reserved.
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Please cite this article as: M. Hayakawa et al., Photochemical addition of cyclic ethers/acetals to olefins using BuOOtBu: Synthesis of masked
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M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
Scheme 1. Three different methods (A, B, and C) for the generation of radicals from cyclic ethers/acetals and their addition to olefins.
The first method (type i) has already been studied for the re-
To overcome the disadvantages of conventional radical addi-
actions shown in Scheme 1 using various radical initiators, mostly
peroxides [3]. However, in these early studies, high temperature
and long reaction times were generally used so that the yields of
the desired products were generally low. Although every effort has
been made toward the improvement of these thermal reactions
using di-tert-butyl peroxide (DTBP) [4] and other peroxides [5],
peracids [6], AIBN [7], and other methods [8], they still cannot avoid
the disadvantages of using high temperatures and/or long reaction
times.
tions to olefins, we report a photochemical reaction using >290 nm
light and DTBP, a commercially available inexpensive reagent
(Scheme 1, method C). This method was applied to the reactions
shown in Scheme 1, which proceeded efficiently at room temper-
ature to give the desired products in good to excellent yield over a
short reaction time; efficient reactions were completed within
0.5 h at room temperature in >95% yield. Scheme 2 shows a plau-
sible mechanism for the reaction. The reaction was initiated by the
photochemical cleavage of DTBP to form t-BuOꢀ radicals [20]. The
The generation of carbon radicals via the photochemical exci-
resulting t-BuOꢀ radicals abstract an
a-hydrogen in cyclic ethers/
tation of ketones and successive abstraction of
a
-hydrogen of het-
acetals 2 [21] to generate its corresponding carbon radical (2′),
which successively adds to olefin 1 to give the desired products 3
via radical 3′ and its H abstraction [22]. The t-BuOH formed during
the reaction can be easily removed by evaporation. The use of
>290 nm light has the advantage of avoiding any undesirable
photochemical side reactions of various functional groups because
this wavelength of light is not absorbed by most functional groups.
eroatoms (type ii) has also been studied for a long time [3b,9,10].
Electronically excited ketones induce significant radical nature at
their oxygen and carbon atoms, which enables the abstraction of a
hydrogen atom from the CeH bond by the oxygen atom (Scheme 1,
method A). This reaction has also been used for asymmetric re-
actions [11] and aqueous phase reactions [10o,p], as well as in ad-
ditions to C]N bonds [12]. Recently, in the context of green
chemistry, various photocatalysts using visible light irradiation
have been studied for the generation of carbon radicals (type iii)
and successive addition to olefins (Scheme 1, method B). Tetrabu-
tylammonium decatungstate [3b,9c,13,14] uranyl cation [15], eosin
Y [16], and cyclopropenium ion [17] have been used for hydrogen
abstraction from ethers/acetals. Organic [18] and metal complex
[19] photoredox catalysts are also used for the generation of
hydrogen abstracting species via SET processes. However, type ii
and iii photochemical reactions generally require prolonged irra-
diation times, and most of the photocatalysts are very expensive
and/or not commercially available. In addition, the use of ketones,
aromatic ketones in most cases, in the reaction makes the purifi-
cation of products difficult in many cases.
2. Results and discussion
Addition of cyclic ethers to olefins. The reaction between
dimethyl maleate (1a-cis) and various cyclic ethers was studied,
and the results are shown in Table 1. The irradiation was conducted
with degassed solutions in the presence of 0.5 eq of DTBP under a
nitrogen atmosphere at room temperature using >290 nm light
[22]. The effect of the irradiation time was investigated using the
reaction between 1a-cis and THF (2A) (Entries 1 ꢁ 5). The reaction
was completed within 0.5 h in 98% yield, which was comprised of
two diastereomers 3aA-syn (more polar) and 3aA-anti (less polar)
(ca. 3:2) (Entry 2). To determine the syn and anti configurations of
the diastereomers, NOESY and ROESY measurements of 3aA-syn
Scheme 2. Plausible reaction mechanism.
t
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Table 1
Addition of cyclic ethers to olefinsa.
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M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
Fig. 1. The stable conformation of 3 aA-syn and -anti calculated by DFT using B3LYP functional.
The effect of various olefins was investigated using 2A. Olefins
bearing two electron-withdrawing groups, dimethyl fumarate (1a-
trans) (Entries 13, 14), maleic acid (1b-cis) (Entry 15), and fumaric
acid (1b-trans) (Entry 16) showed almost the same results as 1a-
cis. The isolation of 3bA-syn and -anti was attempted using silica
gel column chromatography, but it was unsuccessful due to the
overlapping of the two isomers. The structure of the two isomers
were confirmed by the hydrolysis of the 3aA-syn and -anti isomers
into their corresponding acids, 3bA-syn and -anti, respectively.
For olefins bearing a single electron-withdrawing group, the
reactions of tert-butyl acrylate (1d) (Entry 17) and tert-butyl crot-
onate (1e) were completed within a short time and gave their
corresponding products in moderate yield (Entries 18 ꢁ 21), but the
expected product 3fA was not obtained from tert-butyl methacry-
late (1f) (Entry 22). TLC analysis of these reaction mixtures after the
complete consumption of the olefins showed a significant amount
of products at the origin, which indicates the formation of polymers
and oligomers of the starting olefins [27].
Scheme 3. The addition of cyclic ether radicals to olefins (Path A) and decyclization of
the radical (Path B) [26, 28].
and -anti were conducted but NOE between HC and HA/HB was not
observed (Fig. 1). Therefore, the syn and anti configurations were
tentatively determined upon comparison of the observed and
calculated chemical shifts in 1H NMR spectroscopy. The calculated
chemical shift of HA in their stable conformations showed a
considerable high field shift in 3aA-syn when compared with 3aA-
anti [23], whereas those of HB and HC were similar between the
two diastereomers (Fig. 1). The more polar diastereomer showed a
larger high field shift of HA in the observed chemical shift [24] and
was assigned as the syn isomer. The products, 3aA-syn and 3aA-
anti, were photochemically stable and did not decompose upon
prolonged irradiation (Entries 2 ꢁ 5).
Addition of cyclic acetals to olefins. The reactions of various
cyclic acetals and olefins were carried out (Table 2). The reaction of
1,3-dioxolane (2F) and 1a-cis was completed within 0.5 h with the
quantitative formation of three products 3aF-major, 3aF-syn, and
3aF-anti, in which 3aF-major was the predominant product (Entry
1). In addition, the products did not decompose upon prolonged
irradiation (Entry 2). In the case of 2-methyl-1,3-dioxolane (2G)
(Entry 3), 3aG was obtained in an almost quantitative yield upon
0.5 h of irradiation. When the 2-methyl substituent of 2G was
changed to n-hexyl (2H) or iso-propyl (2I), the expected products
3aH and 3aI were obtained in good yield, but with some decrease
when compared with 3aG (Entries 4 ꢁ 6). The higher regiose-
lectivity of 2GꢁI at the 2-position compared to unsubstituted 2F
When tetrahydropyran (2B) was used (Entries 6 ꢁ 8), a similar
reaction proceeded to give a diastereomeric mixture of 3aB-syn
and 3aB-anti, which required a longer irradiation time (2 h) and
with a slight decrease in the yield. The reactions using oxepane
(2C), oxocane (2D), and 1, 4-dioxane (2E) gave similar results to 2B
(Entries 9 ꢁ 12). The slow reaction of 2B when compared to 2A can
be explained by (a) the slower abstraction of the a-hydrogen in 2B
can be explained by the faster
a
-hydrogen abstraction by t-BuOꢀ
by t-BuOꢀ radicals compared to 2A [21a] and/or (b) the slower
addition of the 6-membered 2B radical to the olefin compared to
the 5-membered 2A radical [25]. The decrease in the yield observed
for the product obtained from 2B when compared to that from 2A
was attributed to the competition between Path A and B in Scheme
3. Cyclic ether radicals are reported to decyclize into linear radicals
(Scheme 3, Path B, X ¼ CH2) [26] and the slower addition of the 6-
membered compared to 5-membered radicals to olefins (Scheme 3,
Path A, X ¼ CH2) should cause a decrease in the yield of the desired
addition products for 6-membered 2B.
To confirm the absence of any dark reactions, the reactions of
1a-cis and 2B/2C were conducted in the dark at room temperature
for 72 h; for both 2B and 2C, the adducts 3aB-syn/anti and 3aC-syn/
anti were not detected. These results indicate that light irradiation
is indispensable for the reactions.
radicals in the presence of the 2-alkyl substituent [21a]. The steric
effect of the 2-alkyl substituent has a significant effect on the yield
of the products; larger substituents probably suppress the addition
reaction (Scheme 3, Path A, X ¼ O) and increase the ratio of the
decyclization pathway [28] (Scheme 3, Path B, X ¼ O).
CeC bond formation between the 4-position of 1,3-dioxolane/
1,3-dioxane and 1a-cis was attempted by blocking the 2-position
with two methyl substituents in 2,2-dimethyl-1,3-dioxolane (2J)
(Entries 7 ꢁ 9) and 2,2-dimethyl-1,3-dioxane (2K) (Entries 10, 11).
Similar to that observed for cyclic ethers, a longer irradiation time
was required for 6-membered 2K when compared to 5-membered
2J. Two sets of diastereomeric products, 3aJ-syn and -anti, and
3aK-syn and -anti, were obtained from 2J and 2K, respectively, in
moderate yield. For these acetals, the expulsion of acetone has been
reported via a decyclization of their corresponding cyclic radicals
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Table 2
Addition of cyclic acetals to olefinsa.
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6
M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
investigate the scope of this reaction in acyclic ethers. The result
showed the formation of two unexpected compounds 3aL-a and
3aL-b (Equation (1)). The most probable pathways for the forma-
tion of these products are two types of intramolecular H abstrac-
tions of intermediate radical 3aL-int, which are shown as paths A
and B in Scheme 5. A similar intramolecular H abstraction as path A
has been reported during the addition of acyclic ethers to hexa-
Scheme 4. Decyclization of 2,2-dimethylꢁ1,3-dioxane [28b].
fluoropropene, in which the ether radicals were generated by g-ray
irradiation [29].
(Scheme 4) [28b], which must have an effect on the yields of the
desired products.
The effect of various olefins was investigated using 2G and 2J.
The trend was similar to that observed with cyclic ethers. Dimethyl
fumarate (1a-trans) bearing two electron-withdrawing groups
showed almost the same results to those observed for 1a-cis (Entry
12). Fumaronitrile (1c) gave a good yield with 2G upon 0.5 h of
irradiation (Entry 13), but a moderate yield with 2J (Entry 12). The
isolation of the 3cJ-syn and -anti isomers using column chroma-
tography was also unsuccessful; only some of 3cJ-anti was isolated
and the other isomers were obtained as a syn and anti mixture. The
reactions of tert-butyl acrylate (1d) (Entry 15) and tert-butyl crot-
onate (1e) (Entry 16) bearing a single electron-withdrawing group
with 2G were completed within 0.5 h, but showed some decrease in
the product yield. In contrast, the addition of 2G to tert-butyl
methacrylate (1f) (Entry 17) did not proceed at all though 1f was
completely consumed within 0.5 h. Similar to the results with cyclic
ethers, TLC analysis of the reaction mixtures showed a significant
amount of products at the origin, which was also attributed to
polymers and oligomers of the starting olefins [27].
3. Conclusion
A fast photochemical CeC bond forming reaction between cyclic
ethers/acetals and olefins proceeds at room temperature using
>290 nm light and DTBP, which gave the expected products in good
to excellent yield; efficient reactions were completed within
0.5 h at room temperature in >95% yield. The acetals were used as
acyl/formyl (reactions at their 2-position) and diol (reactions at
their 4-position) synthons. The yields and irradiation times signif-
icantly depended on the size of the ring, in which 5-membered
rings were found to be the best. The yields were also affected by
the size of the 2-alkyl substituent on the cyclic acetal, which was
attributed to their steric effect. The reaction with an acyclic ether,
di-iso-propyl ether, gave two unexpected products and their plau-
sible reaction mechanism was discussed. The reaction showed a
considerable improvement to conventional carbon radical addition
reactions to olefins, particularly reducing the reaction time and the
use of commercially available and inexpensive DTBP.
Reaction of an acyclic ether and olefin. Although some con-
ventional photochemical CeC bond forming reactions have been
reported between olefins and cyclic ethers and acetals, to the best of
our knowledge, only one reaction has been reported with an acyclic
ether, i.e., with ethyl tert-butyl ether [27], an ether that does not
4. Experimental section
General Remarks. 1H NMR (400 MHz) and 13C NMR (100 MHz)
spectra were recorded on a Bruker AVANCE 400 or a JEOL JNM-
ECX400 spectrometer with CDCl3 or acetone-d6 as solvent. As in-
have hydrogen atoms at one
a-carbon of the ether. Therefore, the
reaction of 1a-cis and diisopropyl ether (2L) was conducted to
ternal standards, TMS (
d
0.0 ppm) in CDCl3 or acetone-d6 (d
Scheme 5. Plausible reaction mechanisms for the formation of 3aL-a and 3aL-b.
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M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
7
2.04 ppm) was used for 1H NMR, and CDCl3 (
d6 (
29.8 ppm) for 13C NMR analyses. HRMS spectra were recorded
d
77.0 ppm) or acetone-
(14.81 mg, 0.10 mmol) in tetrahydropyran (2B, 10 mL). Irradiation
time: 2 h. NMR yield (CDCl3), 74% (syn/anti ¼ 45/29) (conversion:
100%). Eluent for chromatography: hexane/ethyl acetate (14/1 /1/
1).
d
on an Agilent G1969 LC/MDS TOF mass spectrometer. Olefins 1a-cis,
1a-trans, 1b-cis, 1b-trans, 1c, ethers 2A, 2B, 2E, acetals 2F, 2G, 2J,
and DTBP were purchased and used as bought. Olefins 1d, 1e, 1f,
ethers 2A, 2B, 2E, and acetals 2F, 2G, 2J were purchased and
distilled before use. Oxepane (2C) [30], oxocane (2D) [31], 2-n-
hexyl-1,3-dioxolane (2H) [10n], 2-iso-propyl-1,3-dioxolane (2I)
[10n], and 2,2-dimethyl-1,3-dioxane (2K) [32] were synthesized
according to the reported procedures.
3aB-syn: 17.40 mg (38%); colorless oil; 1H-NMR (CDCl3):
d
¼ 1.29e1.43 (m, 1 H), 1.43e1.61 (m, 4 H), 1.81e1.90 (m, 1 H), 2.55
(dd, J ¼ 4.3, 16.8 Hz, 1 H), 2.78 (dd, J ¼ 10.3, 16.8 Hz, 1 H), 3.03 (ddd,
J ¼ 4.3, 6.0, 10.3 Hz, 1 H), 3.67 (s, 3 H), 3.72 (s, 3 H), 3.41 (ddd, J ¼ 2.6,
11.5, 11.5 Hz, 1 H), 3.52 (ddd, J ¼ 1.9, 6.0, 10.9 Hz, 1 H), 3.98 (ddd,
J ¼ 2.0, 4.0, 11.5 Hz, 1 H) ppm. 13C-NMR (CDCl3):
¼ 23.3, 25.7, 28.4,
d
General procedure for the photolysis. An ether or acetal (2A-L)
(10 mL) solution of olefin (1a-f) (0.2 mmol) and DTBP (0.1 mmol)
was introduced into a quartz cylindrical cell (diameter: 3 cm)
equipped with a three-way stopcock. The three-way stopcock was
connected to the cell, a nitrogen source, and small vacuum pump.
The solution was evacuated to about 50 mmHg under sonication for
5s and nitrogen was then introduced into the cell; this cycle was
repeated 10 times. The photolysis was conducted using a 500-W
xenon lamp (USHIO Optical Modulex SX-UI500XQ) fitted with an
18-cm water filter and a cut-off filter (Toshiba UV-29) under a ni-
trogen atmosphere. The irradiated light intensity was 20 mW/cm2,
which was measured by an Ushio UIT-150-A Ultraviolet Radiometer
equipped with a UVD-S365 photo detector. After photolysis, the
ether or acetal was removed in vacuo at 40e50 ꢂC/< 150 Torr (most
of the products were volatile under reduced pressure) and the
consumption of the olefin and the products yield were determined
by NMR spectroscopy using a precise amount of naphthalene as an
internal standard; the yields of each product were calculated based
on the consumed starting material. The isolation of the products
was conducted using silica gel column chromatography.
32.1, 46.9, 51.8, 51.9, 68.9, 77.7, 172.5, 173.3 ppm. IR (KBr disk): 2951,
2849, 1738, 1437, 1414, 1368, 1356, 1333, 1258, 1209, 1194, 1165,
1138, 1088, 1051, 1009, 997, 903, 891, 843 cmꢁ1. MS (m/z, relative
intensity): 41 (70), 42 (20), 43 (57), 53 (25), 55 (75), 56 (39), 57 (56),
59 (51), 67 (57), 69 (40), 83 (42), 84 (20), 85 (97), 86 (35), 87 (27), 97
(20), 111 (44), 114 (47), 115 (40), 125 (83), 138 (20), 157 (100), 158
(28), 170 (22), 199 (42), 230 (Mþ, 0.02).
3aB-anti: 10.10 mg (22%); colorless oil; 1H-NMR (CDCl3):
d
¼ 1.29e1.42 (m, 1 H), 1.42e1.60 (m, 4 H), 1.78e1.91 (m, 1 H), 2.69
(dd, J ¼ 4.8, 16.9 Hz, 1 H), 2.78 (dd, J ¼ 9.4, 16.9 Hz, 1 H), 2.91 (ddd,
J ¼ 4.8, 6.4, 9.4 Hz, 1 H), 3.67 (s, 3 H), 3.71 (s, 3 H), 3.39 (ddd, J ¼ 3.0,
11.3, 11.3 Hz, 1 H), 3.52 (ddd, J ¼ 1.9, 6.4, 10.8 Hz, 1 H), 3.95 (ddd,
J ¼ 2.0, 2.0, 11.3 Hz, 1 H) ppm. 13C-NMR (CDCl3):
¼ 23.2, 25.7, 29.5,
d
32.2, 47.3, 51.7, 52.0, 68.8, 77.5,172.9,173.5 ppm. IR (KBr disk): 2995,
2953, 2851, 1738, 1437, 1416, 1368, 1358, 1341, 1285, 1265, 1209,
1200, 1163, 1088, 1045, 1011, 997, 899, 887, 851 cmꢁ1. MS (m/z,
relative intensity): 41 (69), 42 (15), 43 (53), 44 (20), 53 (18), 55 (75),
56 (29), 57 (51), 59 (44), 67 (52), 69 (29), 83 (32), 85 (99), 86 (25), 87
(19), 111 (34), 114 (38), 115 (30), 125 (81), 157 (100), 158 (19), 170
(15), 199 (31), 230 (Mþ, 0.02). HRMS: m/z calcd. for C11H18O5:
230.1154; found: 230.1144.
4.1. 2-(Tetrahydro-2-furanyl)butanedioic acid 1,4-dimethyl ester
(3aA-syn, anti) [5d,7c,19b,33]
Dimethyl maleate (1a-cis, 28.56 mg, 0.20 mmol) and DTBP
(14.36 mg, 0.10 mmol) in THF (2A, 10 mL). Irradiation time: 0.5 h.
NMR yield (CDCl3), 98% (syn/anti ¼ 60/38) (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (14/1 / 1/1).
3aA-syn: 22.17 mg (52%); colorless oil; 1H-NMR (CDCl3):
4.3. 2-(2-Oxepanyl)butanedioic acid 1,4-dimethyl ester (3aC-syn,
anti)
Dimethyl maleate (1a-cis, 28.82 mg, 0.20 mmol) and DTBP
(14.85 mg, 0.10 mmol) in oxepane (2C, 10 mL). Irradiation time: 2 h.
NMR yield (CDCl3), 67% (syn/anti ¼ 33/34) (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (40/1 / 0/1).
3aC-syn: 13.95 mg (29%); colorless oil; 1H-NMR (CDCl3):
d
¼ 1.59e1.70 (m, 1 H), 1.83e1.99 (m, 3 H), 2.48 (dd, J ¼ 4.5, 16.6 Hz,
1 H), 2.78 (dd, J ¼ 10.2, 16.6 Hz, 1 H), 3.09 (ddd, J ¼ 4.5, 6.6, 10.2 Hz,
1 H), 3.68 (s, 3 H), 3.73 (s, 3 H), 3.74 (ddd, J ¼ 7.0, 7.0, 14.9 Hz, 1 H),
3.87 (ddd, J ¼ 6.7, 8.3, 14.9 Hz, 1 H), 4.06 (ddd, J ¼ 6.0, 6.0, 6.6 Hz,
1 H) ppm. 13C-NMR (CDCl3):
d
¼ 25.6, 28.6, 32.5, 46.0, 51.9, 52.0,
d
¼ 1.40e1.81 (m, 8H), 2.52 (dd, J ¼ 16.8, 4.4 Hz, 1H), 2.78 (dd,
68.4, 78.9, 172.2, 173.3 ppm. IR (KBr disk): 2953, 2876, 1740, 1730,
1460, 1439, 1414, 1360, 1346, 1317, 1263, 1196, 1165, 1069, 1020,
1005, 926, 849 cmꢁ1. MS, m/z (relative intensity): 45 (7), 55 (41), 59
(27), 70 (14), 71 (100), 72 (13), 97 (11), 111 (30), 114 (14), 143 (55),
153 (13), 185 (20), 216 (Mþ, 3), 217 (Mþþ1, 8).
J ¼ 16.8, 10.8 Hz, 1H), 3.01 (ddd, J ¼ 10.8, 6.6, 4.4 Hz, 1H), 3.53 (ddd,
J ¼ 4.8, 6.8, 11.9 Hz, 1H), 3.67 (s, 3H), 3.64e3.71 (m, 1H), 3.72 (s, 3H),
3.85 (ddd, J ¼ 4.8, 6.6, 11.9 Hz, 1H) ppm. 13C-NMR (CDCl3):
¼ 26.1,
d
26.3, 30.6, 32.7, 32.8, 47.6, 51.8, 51.9, 69.5, 79.4, 172.5, 173.5 ppm. IR
(KBr disk): 3633, 3562, 3459, 2932, 2857, 1738, 1437, 1414, 1362,
1334, 1262, 1198, 1168, 1118, 1003, 971, 900, 873, 846, 686, 591, 534,
488, 405 cmꢁ1. MS, m/z (relative intensity): 41 (44), 42 (42), 43 (33),
55 (100), 57 (14), 59 (26), 69 (11), 71 (11), 81 (65), 83 (15), 87 (10),
99 (80), 114 (23), 115 (39), 139 (29), 171 (30). HRMS: m/z calcd. for
3aA-anti: 12.83 mg (30%); colorless oil; 1H-NMR (CDCl3):
d
¼ 1.67e1.78 (m, 1H), 1.82e1.94 (m, 2 H), 1.94e2.04 (m, 1 H), 2.70
(dd, J ¼ 4.7, 16.7 Hz, 1 H), 2.80 (dd, J ¼ 9.3, 16.7 Hz, 1 H), 2.92 (ddd,
J ¼ 4.7, 7.6, 9.3 Hz, 1 H), 3.68 (s, 3 H), 3.72 (s, 3 H), 3.73 (ddd, J ¼ 7.0,
7.0, 14.9 Hz, 1 H), 3.81 (ddd, J ¼ 6.8, 8.3, 14.9 Hz, 1 H), 4.01 (ddd,
C
12H20O5 þ Na: 267.1208; found: 267.12028.
J ¼ 1.0, 6.9, 7.6 Hz, 1 H) ppm. 13C-NMR (CDCl3):
d
¼ 25.6, 29.6, 33.2,
3aC-anti: 15.76 mg (32%); colorless oil; 1H-NMR (CDCl3):
¼ 1.40e1.80 (m, 8H), 2.71 (dd, J ¼ 5.6, 16.8 Hz, 1H), 2.77 (dd,
46.6, 51.8, 52.0, 68.1, 78.7, 172.6, 173.3 ppm. IR (KBr disk): 2953,
2876, 1738, 1732, 1460, 1439, 1414, 1360, 1348, 1319, 1263, 1200,
1165, 1067, 1028, 1007, 968, 924, 891, 849 cmꢁ1. MS, m/z (relative
intensity): 45 (3), 55 (16), 59 (13), 71 (100), 72 (5), 97 (4), 111 (10),
114 (3), 143 (15), 185 (6), 217 (Mþþ1, 2).
d
J ¼ 8.4, 16.8 Hz, 1H), 2.92 (ddd, J ¼ 5.6, 7.2, 8.4 Hz, 1H), 3.50 (ddd,
J ¼ 6.2, 6.8, 10.4 Hz, 1H), 3.68 (s, 3H), 3.71 (s, 3H), 3.65e3.74 (m, 1H),
3.80 (ddd, J ¼ 7.2, 7.2, 10.4 Hz, 1H) ppm. 13C-NMR (CDCl3):
¼ 26.16,
d
26.24, 30.7, 32.7, 33.7, 47.8, 51.8, 52.0, 69.0, 79.1, 172.9, 173.8 ppm. IR
(KBr disk): 2932, 2857, 1738, 1437, 1367, 1343, 1261, 1200,1163, 1114,
1027,1003, 971, 850, 537, 474, 411 cmꢁ1. MS, m/z (relative intensity):
41 (48), 42 (42), 43 (35), 55 (100), 57 (14), 59 (27), 69 (12), 71 (12),
81 (69), 83 (16), 87 (11), 99 (83),114 (24),115 (41),139 (28),171 (32).
HRMS: m/z calcd. for C12H20O5 þ Na: 267.1208; found: 267.1209.
4.2. 2-(Tetrahydro-2H-pyran-2-yl)butanedioic acid 1,4-dimethyl
ester (3aB-syn, anti) [19b]
Dimethyl maleate (1a-cis, 28.83 mg, 0.20 mmol) and DTBP
t
Please cite this article as: M. Hayakawa et al., Photochemical addition of cyclic ethers/acetals to olefins using BuOOtBu: Synthesis of masked
ketones/aldehydes and diols, Tetrahedron, https://doi.org/10.1016/j.tet.2020.131557

8
M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
4.4. 2-(2-Oxocanyl)butanedioic acid 1,4-dimethyl ester (3aD-syn,
anti)
4.6. 2-(Tetrahydro-2-furanyl)butanedioic acid 1,4-dimethyl ester
(3aA-syn, anti) [5d,7c,19b,33]
Dimethyl maleate (1a-cis, 29.00 mg, 0.20 mmol) and DTBP
(14.70 mg, 0.10 mmol) in oxocane (2D, 10 mL). Irradiation time: 2 h.
NMR yield (CDCl3), 56% (syn/anti ¼ 29/27) (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (40/1 / 0/1).
3aD-syn: 14.03 mg (27%); colorless oil; 1H-NMR (CDCl3):
Dimethyl fumarate (1a-trans, 28.86 mg, 0.20 mmol) and DTBP
(14.67 mg, 0.10 mmol) in THF (2A, 10 mL). Irradiation time: 0.5 h.
NMR yield (CDCl3), 95% (syn/anti ¼ 45/50) (conversion: 100%).
d
¼ 1.38e1.83 (m, 10 H), 2.51 (dd, J ¼ 4.4, 16.8 Hz, 1 H), 2.75 (dd,
4.7. 2-(2-Tetrahydro-2-furanyl)butanedioic acid (3bA-syn, anti)
[33a,35]
J ¼ 10.6, 16.8 Hz, 1 H), 2.99 (ddd, J ¼ 4.4, 6.4, 10.6 Hz, 1 H), 3.51 (ddd,
J ¼ 3.4, 6.2, 12.0 Hz, 1 H), 3.67 (s, 3 H), 3.62e3.75 (m, 1 H), 3.72 (s,
3 H), 3.83 (ddd, J ¼ 3.4, 8.4, 12.0 Hz, 1 H) ppm. 13C-NMR (CDCl3):
Maleic acid (1b-cis, 23.20 mg, 0.20 mmol) and DTBP (14.67 mg,
0.10 mmol) in THF (2A, 10 mL). Irradiation time: 0.5 h. NMR yield
(acetone-d6), 96% (syn/anti ¼ 45/51) (conversion: 99.9%).
d
¼ 24.6, 26.5, 26.9, 27.7, 32.0, 32.4, 47.8, 51.8, 51.9, 71.5, 78.8, 172.6,
173.7 ppm. IR (KBr disk): 2925, 2853, 1738, 1437, 1362, 1332, 1261,
1196, 1165, 1098, 1012, 971, 894, 848, 800, 564, 440 cmꢁ1. MS, m/z
(relative intensity): 41 (100), 42 (24), 43 (48), 44 (10), 45 (21), 53
(13), 54 (10), 55 (65), 56 (22), 57 (19), 59 (30), 67 (23), 68 (11), 69
(39), 71 (16), 79 (11), 83 (15), 95 (66), 113 (51), 114 (20), 115 (37), 143
(11), 260 (Mþþ1 0.04). HRMS: m/z calcd. for C13H22O5: 259.1545;
found: 259.1563.
4.8. 2-(2-Tetrahydro-2-furanyl)butanedioic acid (3bA-syn, anti)
[33a,35]
Fumaric acid (1b-trans, 23.11 mg, 0.20 mmol) and DTBP
(14.67 mg, 0.10 mmol) in THF (2A, 10 mL). Irradiation time: 0.5 h.
NMR yield (acetone-d6), 100% (syn/anti ¼ 45/55) (conversion:
100%).
3aD-anti: 13.51 mg (26%); colorless oil; 1H-NMR (CDCl3):
¼ 1.38e1.85 (m, 10 H), 2.68 (dd, J ¼ 4.8, 16.4 Hz, 1 H), 2.77 (dd,
d
J ¼ 9.6, 16.4 Hz, 1 H), 2.87 (ddd, J ¼ 4.8, 6.4, 9.6 Hz, 1 H), 3.46 (ddd,
J ¼ 3.4, 6.8, 12.0 Hz, 1 H), 3.67 (s, 3 H), 3.68e3.75 (m, 1 H), 3.71 (s,
3 H), 3.83 (ddd, J ¼ 3.2, 8.0, 12.0 Hz, 1 H) ppm. 13C-NMR (CDCl3):
d
¼ 24.6, 26.4, 26.9, 28.0, 32.5, 33.1, 48.3, 51.8, 51.9, 71.6, 79.1, 172.9,
4.9. Tetrahydro-2-furan propanoic acid tert-butyl ester (3dA)
174.0 ppm. IR (KBr disk): 2959, 2923, 2852, 1731, 1455, 1260, 1096,
1020, 799 cmꢁ1. MS, m/z (relative intensity): 41 (100), 42 (25), 43
(48), 45 (21), 53 (12), 54 (10), 55 (69), 56 (26), 57 (18), 59 (30), 67
(21), 68 (10), 69 (38), 71 (16), 79 (11), 83 (17), 87 (10), 95 (66), 113
(51),114 (20), 115 (43),142 (10), 143 (14), 259 (Mþ, 0.07). HRMS: m/z
calcd. for C13H22O5: 259.1545; found: 259.1534.
tert-Butyl acrylate (1d, 25.60 mg, 0.20 mmol) and DTBP
(14.67 mg, 0.10 mmol) in THF (2A, 10 mL). Irradiation time: 1 h.
NMR yield (CDCl3), 40% (conversion: 100%). Eluent for chroma-
tography: hexane/ethyl acetate (80/1 / 0/1).
3dA: 13.23 mg (33%); colorless oil; 1H-NMR (
d, CDCl3): 1.44 (s,
9 H),1.39e1.52 (m,1 H), 1.79 (ddd, J ¼ 6.4, 7.6, 7.6 Hz, 2 H),1.82e1.93
(m, 2 H), 1.93e2.03 (m, 1 H), 2.28 (dt, J ¼ 7.6, 15.2 Hz, 1 H), 2.36 (dt,
J ¼ 7.6, 15.2 Hz, 1 H), 3.72 (ddd, J ¼ 6.4, 7.9, 7.9 Hz, 1 H), 3.78e3.88
4.5. 2-(1, 4-Dioxan-2-yl)butanedioic acid dimethyl ester (3aE-syn,
anti) [14b,19b,34]
(m, 2 H) ppm. 13C-NMR (
d, CDCl3): 25.7, 28.1, 30.8, 31.1, 32.4, 67.6,
Dimethyl maleate (1a-cis, 28.60 mg, 0.20 mmol) and DTBP
(14.54 mg, 0.10 mmol) in 1,4-dioxane (2E, 10 mL). Irradiation time:
2 h. NMR yield (CDCl3), 66% (syn/anti ¼ 38/28) (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (14/1 / 1/1).
3aE-syn: 14.24 mg (31%); colorless oil; 1H-NMR (CDCl3):
78.3, 80.1, 172.9 ppm. IR (KBr disk): 2974, 2870, 1726, 1457, 1391,
1365,1256,1148,1113,1070,1020, 958, 917, 849, 756, 462, 431 cmꢁ1
.
MS (m/z, relative intensity): 41 (42), 42 (11), 43 (35), 44 (4), 55 (12),
56 (10), 57 (55), 70 (4), 71 (100), 72 (4), 73 (8), 81 (7), 84 (7), 85 (23),
97 (10), 98 (6),101 (4),116 (15),125 (7),127 (38),143 (6),144 (9),145
(9). HRMS: m/z calcd. for C11H20O3: 201.1472; found: 201.1490.
d
¼ 2.53 (dd, J ¼ 4.6, 16.9 Hz, 1 H), 2.84 (dd, J ¼ 10.0, 16.9 Hz, 1 H),
3.03 (ddd, J ¼ 4.6, 5.4, 10.0 Hz, 1 H), 3.46 (dd, J ¼ 10.1, 11.5 Hz, 1 H),
3.57 (ddd, J ¼ 2.9, 11.5, 11.5 Hz, 1 H), 3.66e3.72 (m, 2H), 3.68 (s, 3 H),
3.74 (s, 3 H), 3.73e3.83 (m, 3H) ppm. 13C-NMR (CDCl3):
d
¼ 32.3,
43.5, 52.0, 52.2, 66.3, 67.2, 68.7, 75.3,172.0, 172.3 ppm. IR (KBr disk):
2957, 2914, 2859, 1738, 1439, 1414, 1366, 1337, 1302, 1277, 1258,
1234, 1200, 1169, 1119, 1043, 1005, 970, 941, 920, 905, 880, 849,
619 cmꢁ1. MS, m/z (relative intensity): 41 (52), 42 (26), 43 (65), 44
(30), 45 (49), 53 (21), 55 (83), 58 (26), 59 (75), 69 (22), 71 (28), 83
(30), 86 (50), 87 (100), 96 (46), 97 (61), 99 (26), 113 (26), 114 (90),
115 (61), 125 (29), 129(70), 146 (36),157 (67), 172 (87), 200 (52), 201
(37), 232 (Mþ, 0.1).
4.10. Tetrahydro-b-methyl-2-furanpropanoic acid tert-butyl ester
(3eA-syn, anti)
tert-Butyl crotonate (1e, 28.37 mg, 0.20 mmol) and DTBP
(14.57 mg, 0.10 mmol) in THF (2A, 10 mL). Irradiation time: 1 h.
NMR yield (CDCl3), 48% (syn/anti ¼ 24/24) (conversion: 93%). Eluent
for chromatography: hexane/ethyl acetate (80/1 / 0/1). 3eA-syn þ
3eA-anti: 10.60 mg (30%; syn/anti ¼ 1/1); colorless oil. The ob-
tained two products were further separated by column chroma-
tography: hexane/ethyl acetate (80/1 / 20/1). Only a part of 3eA-
anti was isolated by the second chromatographic separations and
the rest of 3eA-anti and 3eA-syn were obtained as a mixture.
3aE-anti: 9.79 mg (21%); colorless oil; 1H-NMR (CDCl3):
d
¼ 2.71
(dd, J ¼ 4.7, 17.0 Hz, 1 H), 2.80 (dd, J ¼ 9.2, 17.0 Hz, 1 H), 2.93 (ddd,
J ¼ 4.7, 7.1, 9.2 Hz, 1 H), 3.39 (dd, J ¼ 10.3, 11.9 Hz, 1 H), 3.57 (ddd,
J ¼ 2.9, 11.7, 11.7 Hz, 1 H), 3.66e3.71 (m, 2H), 3.68 (s, 3 H), 3.72 (s,
3 H), 3.74e3.81 (m, 3H) ppm. 13C-NMR (CDCl3):
d
¼ 31.9, 43.6, 51.9,
3eA-anti: 1H-NMR (
d
, CDCl3): 0.91 (d, J ¼ 6.4 Hz, 3 H), 1.45 (s,
52.3, 66.3, 67.0, 69.5, 74.6, 172.47, 172.52 ppm. IR (KBr disk): 2957,
2914, 2857, 1738, 1439, 1416, 1364, 1344, 1300, 1277, 1258, 1198,
1167, 1119, 1063, 1026, 1009, 957, 916, 905, 878, 847, 617 cmꢁ1. MS,
m/z (relative intensity): 41 (44), 42 (21), 43 (60), 44 (30), 45 (39), 55
(84), 59 (72), 71 (22), 83 (23), 86 (39), 87 (100), 96 (36), 97 (52), 114
(90), 115 (52), 125 (37), 129(60), 146 (24), 157 (54), 172 (84), 200
(48), 201 (32), 232 (Mþ, 0.1).
9 H), 1.46e1.64 (m, 1 H), 1.80e1.96 (m, 3 H), 1.95e2.08 (m, 1 H), 2.00
(dd, J ¼ 8.8, 10.0 Hz, 1 H), 2.52 (dd, J ¼ 8.8, 10.0 Hz, 1 H), 3.56 (ddd,
J ¼ 7.1, 7.1, 7.1 Hz, 1 H), 3.72 (ddd, J ¼ 6.1, 7.7, 8.4 Hz, 1 H), 3.81 (ddd,
J ¼ 6.8, 6.8, 8.4 Hz, 1 H) ppm.
3eA-syn þ 3eA-anti: 1H-NMR (
, CDCl3): 0.99 (d, J ¼ 6.4 Hz, 3 H),
d
1.45 (s, 9 H), 1.78e2.06 (m, 5 H), 2.06e2.18 (m, 1 H), 2.33 (dd, J ¼ 4.8,
14.4 Hz, 1 H), 3.64e3.76 (m, 2 H), 3.79e3.87 (m, 1 H) ppm.
t
Please cite this article as: M. Hayakawa et al., Photochemical addition of cyclic ethers/acetals to olefins using BuOOtBu: Synthesis of masked
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M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
9
4.11. 2-(1,3-dioxolan-4-yl)butanedioic acid 1,4-dimethyl ester (3aF-
syn, anti) [19b] and 2-(1,3-dioxolan-2-yl)butanedioic acid 1,4-
dimethyl ester (3aF-major) [5d,h,19b,36]
(44), 89 (11), 97 (13), 99 (22), 103 (15), 110 (5), 111 (12), 113 (23), 114
(7), 129 (23), 142 (5), 143 (10), 157 (56), 158 (11), 170 (15), 185 (39),
217 (5), 233 (Mþþ1, 0.08).
Dimethyl maleate (1a-cis, 28.99 mg, 0.20 mmol) and DTBP
(14.63 mg, 0.10 mmol) in 1,3-dioxolane (2F, 10 mL). Irradiation
time: 1 h. NMR yield (CDCl3), 100% (syn/anti/major ¼ 8/4/88)
(conversion: 100%). Eluent for chromatography: hexane/ethyl ace-
tate (14/1 / 2/1). 3aF-major þ 3aF-syn þ 3aF-anti: 41.64 mg
(95%). The obtained three products were further separated by col-
umn chromatography: hexane/ethyl acetate (8/1 / 1/1). Only a
part of 3aF-major was isolated by the second chromatographic
separations and 3aF-syn and eanti, and the rest of 3aF-major were
obtained as a mixture.
4.13. 2-(2-Hexyl-1, 3-dioxolan-2-yl)butanedioic acid 1,4-dimethyl
ester (3aH)
Dimethyl maleate (1a-cis, 28.91 mg, 0.20 mmol) and DTBP
(14.77 mg, 0.10 mmol) in 2-hexyl-1,3-dioxolane (2H, 10 mL). Irra-
diation time: 0.5 h. NMR yield (CDCl3), 77% (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (20/1 / 0/1).
3aH: 45.75 mg (75%); colorless oil. 1H-NMR (
d, CDCl3): 0.88 (t,
J ¼ 6.9 Hz, 3H), 1.18e1.49 (m, 8H), 1.58e1.77 (m, 2H), 2.61 (dd,
J ¼ 4.6, 16.9 Hz, 1H), 2.86 (dd, J ¼ 10.5, 16.9 Hz, 1H), 3.25 (dd, J ¼ 4.6,
10.5 Hz, 1H), 3.67 (s, 3H), 3.74 (s, 3H) 3.90e4.07 (m, 4H) ppm. 13C-
3aF-major: 19.77 mg (45%); colorless oil; 1H-NMR (
d, CDCl3):
2.63 (dd, J ¼ 4.8, 16.9 Hz, 1 H), 2.81 (dd, J ¼ 9.2, 16.9 Hz, 1 H), 3.25
(ddd, J ¼ 4.2, 4.8, 9.2 Hz, 1 H), 3.69 (s, 3 H), 3.75 (s, 3H), 3.85e3.92
(m, 2H), 3.92e4.02 (m, 2H), 5.20 (d, J ¼ 4.2 Hz, 1H) ppm. 13C-NMR
NMR (d, CDCl3): 14.0, 22.5, 22.7, 29.3, 31.7, 32.2, 35.4, 48.6, 51.8, 52.1,
65.4, 65.5, 110.4, 172.3, 172.7 ppm. IR (KBr): 2954, 2932, 2872, 2858,
1741, 1459, 1438, 1415, 1350, 1301, 1266, 1206, 1166, 1096, 1039,
1004, 950, 898, 870, 852, 822, 775, 730, 569, 422 cmꢁ1. MS (m/z,
relative intensity): 55 (23), 99 (16), 113 (10), 157 (100), 185 (24), 217
(7), 303 (0.05, Mþþ1). HRMS: m/z calcd. for C15H26O6 þ Na:
325.1627; found: 325.1642.
(d, CDCl3): 30.0, 45.6, 51.8, 52.2, 65.3, 102.7, 171.3, 172.3 ppm. IR (KBr
disk): 2994, 2955, 2893, 1738, 1439, 1395, 1364, 1327, 1267, 1227,
1194, 1165, 1148, 1105, 1036, 999, 984, 945, 897, 853, 756, 667, 554,
480 cmꢁ1. MS (m/z, relative intensity): 40 (14), 41 (28), 42 (28), 43
(41), 44 (29), 45 (67), 46 (13), 53 (11), 54 (10), 55 (48), 56 (10), 59
(38), 69 (11), 71 (13), 73 (100), 74 (32), 75 (11), 83 (14), 87 (26), 99
(31), 103 (18), 113 (37), 114 (18), 115 (18), 127 (10), 145 (27), 157 (11),
187 (21), 219 (0.14, Mþ).
4.14. 2-(2-Isopropyl-1, 3-dioxolan-2-yl)butanedioic acid 1,4-
dimethyl ester (3aI)
3aF-major þ 3aF-syn þ3aF-anti: 19.77 mg (45%, major/syn/
Dimethyl maleate (1a-cis, 28.83 mg, 0.20 mmol) and DTBP
(14.95 mg, 0.10 mmol) in 2-isopropyl-1,3-dioxolane (2I, 10 mL).
Irradiation time: 0.5 h. NMR yield (CDCl3), 52% (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (10/1 / 0/1).
anti ¼ 71/10/19); colorless oil
3aF-syn: 1H-NMR (
(dd, J ¼ 4.3,16.8 Hz,1 H), 3.17e3.22 (m,1H), 3.69 (s, 3H), 3.74 (s, 3H),
3.8e3.84 (m,1H), 3.87e4.02 (m,1H), 4.27e4.32 (m,1H), 4.81 (s,1H),
5.05 (s, 1H).
d
, CDCl3): 2.52 (dd, J ¼ 4.8, 16.8 Hz, 1 H), 2.65
3aI: 25.09 mg (48%); colorless oil. 1H-NMR (
d, CDCl3): 0.94 (d,
J ¼ 6.9, 3H), 0.99 (d, J ¼ 6.4, 3H), 2.05 (dq, J ¼ 6.4, 6.9 Hz, 1H), 2.58
(dd, J ¼ 4.1, 17.1 Hz, 1H), 2.90 (dd, J ¼ 10.6, 17.1 Hz, 1H), 3.42 (dd,
J ¼ 4.1,10.6 Hz,1H), 3.67 (s, 3H) 3.73 (s, 3H), 3.94e4.09 (m, 4H) ppm.
3aF-major þ 3aF-syn þ3aF-anti: MS (m/z, relative intensity):
40 (13), 41 (30), 42 (19), 43 (59), 44 (96), 45 (100), 55 (39), 59 (31),
71 (10), 73 (45), 87 (12), 97 (20), 99 (15), 113 (24), 114 (34), 125 (16),
129 (10), 146 (10), 156 (19), 219 (0.07, Mþ).
13C-NMR (
d, CDCl3): 16.9, 17.1, 32.2, 35.9, 47.8, 51.8, 52.1, 66.4, 66.6,
112.7, 172.6, 172.7 ppm. IR (KBr): 3636, 3552, 3458, 2954, 2898,
2850, 1739, 1471, 1437, 1415, 1384, 1359,1266, 1207, 1161, 1087, 1033,
991, 956, 900, 881, 848, 762, 686, 597, 570, 502, 469, 444 cmꢁ1. MS
(m/z, relative intensity): 43 (81), 55 (28), 71 (15), 99 (14), 115 (100),
185 (25), 259 (0.17, Mþ). HRMS: m/z calcd. for C12H20O6 þ H:
261.1338; found: 261.1333.
Pure 3aF-anti was isolated from other experiment.
3aF-anti: 1H-NMR (
d
, CDCl3): 2.76 (dd, J ¼ 5.0, 16.9 Hz, 1 H), 2.85
(dd, J ¼ 7.8, 16.9 Hz, 1 H), 2.98 (ddd, J ¼ 5.0, 7.8, 8.2 Hz, 1 H), 3.69 (s,
3H), 3.72 (s, 3H), 3.79 (dd, J ¼ 5.5, 8.7 Hz, 1 H), 4.03 (dd, J ¼ 6.4,
8.7 Hz, 1 H), 4.25 (ddd, J ¼ 5.5, 6.4, 8.2 Hz, 1 H), 4.83 (s, 1H), 5.00 (s,
1H) ppm. 13C-NMR (
d, CDCl3): 32.5, 45.0, 51.9, 52.3, 69.0, 74.8, 95.1,
172.2, 172.3 ppm. IR (KBr disk): 2999, 2955, 2876, 2860, 1738, 1730,
1462, 1438, 1414, 1368, 1265, 1202, 1167, 1088, 1024, 941, 851,
735 cmꢁ1. MS (m/z, relative intensity): 45 (100), 55 (43), 59 (41), 69
(13), 71 (14), 73 (61), 87 (18), 97 (20), 99 (16), 113 (32), 114 (31), 125
(18), 128 (11), 129(14), 145 (11), 146 (15), 156 (32), 187 (13), 219 (0.6,
Mþ).
4.15. 2-(2, 2-Dimethyl-1, 3-dioxolan-4-yl)butanedioic acid 1,4-
dimethyl ester (3aJ-syn, anti)
Dimethyl maleate (1a-cis, 28.69 mg, 0.20 mmol) and DTBP
(14.77 mg, 0.10 mmol) in 2, 2-dimethyl-1, 3-dioxolane (2J, 10 mL).
Irradiation time: 0.75 h. NMR yield (CDCl3), 26% (syn/anti ¼ 18/8)
(conversion: 100%). Eluent for chromatography: hexane/ethyl ace-
tate (20/1 / 0/1).
4.12. 2-(2-Methyl-1, 3-dioxolan-2-yl)butanedioic acid 1,4-dimethyl
ester (3aG) [5h,37]
3aJ-syn: 7.30 mg (15%); colorless oil; 1H-NMR (
d, CDCl3): 1.33 (s,
3H), 1.41 (s, 3H), 2.52 (dd, J ¼ 4.4, 16.8 Hz, 1H), 2.79 (dd, J ¼ 9.8,
16.8 Hz, 1H), 3.20 (ddd, J ¼ 4.4, 5.8, 9.8 Hz, 1H), 3.69 (s, 3H), 3.73 (s,
3H) 3.80 (dd, J ¼ 6.0, 8.8 Hz, 1H), 4.01 (dd, J ¼ 6.4, 8.8 Hz, 1H), 4.36
Dimethyl maleate (1a-cis, 28.56 mg, 0.20 mmol) and DTBP
(14.51 mg, 0.10 mmol) in 2-methyl-1,3-dioxolane (2G, 10 mL).
Irradiation time: 0.5 h. NMR yield (CDCl3), 97% (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (14/1 / 2/1).
(ddd, J ¼ 5.8, 6.0, 6.4 Hz, 1H) ppm. 13C-NMR (
d, CDCl3): 24.9, 26.2,
31.8, 44.2, 52.0, 52.2, 66.3, 75.1, 109.5, 172.1, 172.5 ppm. IR (KBr
disk): 3855, 3630, 3457, 2988, 2954, 2359, 1737, 1438, 1372, 1257,
1210, 1164, 1063, 1007, 915, 853, 797, 642, 595, 548, 457, 431,
416 cmꢁ1. MS (m/z, relative intensity): 43 (100), 55 (11), 59 (18), 72
(17), 97 (15), 101 (13), 129 (11), 157 (33), 171 (22), 231 (13), 245 (0.2,
3aG: 43.72 mg (95%); colorless oil. 1H-NMR (
d, CDCl3): 1.39 (s,
3H), 2.65 (dd, J ¼ 4.4, 16.9 Hz, 1 H), 2.85 (dd, J ¼ 10.4, 16.9 Hz, 1 H),
3.19 (dd, J ¼ 4.4, 10.4 Hz, 1 H), 3.67 (s, 3 H), 3.74 (s, 3 H), 3.91e4.05
(m, 4 H) ppm. 13C-NMR (
d, CDCl3): 22.0, 32.4, 49.6, 51.8, 52.1, 64.85,
64.90, 108.7, 172.1, 172.5 ppm. IR (KBr): 2992, 2955, 2893, 2851,
1740, 1437, 1416,1383, 1352,1294, 1271, 1211, 1165, 1093, 1043, 1009,
951, 880, 853, 818, 766, 694, 650, 559, 513, 405 cmꢁ1. MS (m/z,
relative intensity): 41 (17), 42 (12), 43 (81), 44 (23), 45 (29), 53 (18),
54 (8), 55 (43), 59 (35), 69 (9), 81 (6), 83 (12), 85 (16), 87 (100), 88
M
þ ꢁ H). HRMS: m/z calcd. for C11H18O6: 246.1103; found: 246.1118.
3aJ-anti: 3.67 mg (8%); colorless oil; 1H-NMR (
d, CDCl3): 1.33 (s,
3H), 1.40 (s, 3H), 2.74 (dd, J ¼ 4.4, 17.0 Hz, 1H), 2.83 (dd, J ¼ 8.2,
17.0 Hz, 1H), 2.97 (ddd, J ¼ 4.4, 8.2, 8.2 Hz, 1H), 3.69 (s, 3H), 3.72 (s,
3H), 3.82 (dd, J ¼ 6.0, 8.8 Hz, 1H), 4.12 (dd, J ¼ 6.4, 8.8 Hz, 1H), 4.28
t
Please cite this article as: M. Hayakawa et al., Photochemical addition of cyclic ethers/acetals to olefins using BuOOtBu: Synthesis of masked
ketones/aldehydes and diols, Tetrahedron, https://doi.org/10.1016/j.tet.2020.131557

10
M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
(ddd, J ¼ 6.0, 6.4, 8.2 Hz, 1H) ppm. 13C-NMR (
d
, CDCl3): 25.2, 26.5,
(conversion: 100%). Eluent for chromatography: hexane/ethyl ace-
32.5, 45.4, 51.8, 52.2, 66.2, 75.0, 109.4, 172.4, 172.5 ppm. IR (KBr
disk): 3630, 3461, 2988, 2954, 1738, 1439, 1414, 1372, 1258, 1211,
1167, 1064,1007, 916, 854, 795, 758, 681, 644, 514, 430 cmꢁ1. MS (m/
z, relative intensity): 43 (100), 55 (12), 59 (20), 72 (18), 97 (15), 101
(13), 111 (10), 129 (16), 157 (11), 171 (39), 246 (0.14, Mþ). HRMS: m/z
calcd. for C11H18O6: 246.1103; found: 246.1080.
tate (1/0 / 0/1).
3cJ-syn: 3.9 mg (10%); colorless oil; 1H-NMR (
d, CDCl3): 1.39 (s,
3H),1.53 (s, 3H), 2.88 (d, J ¼ 7.2 Hz, 2 H), 3.09 (dt, J ¼ 3.2, 7.2 Hz,1 H),
3.96 (dd, J ¼ 5.6, 9.3 Hz,1 H), 4.23 (dd, J ¼ 6.4, 9.3 Hz,1 H), 4.35 (ddd,
J ¼ 3.2, 5.6, 6.4 Hz, 1 H) ppm. 13C-NMR (
d, CDCl3): 18.3, 25.0, 26.1,
33.0, 66.9, 73.1, 111.3, 115.5, 116.2 ppm. IR (KBr disk): 2989, 2939,
2251, 1458, 1423, 1375, 1260, 1220, 1152, 1111, 1062, 972, 933, 844,
511 cmꢁ1. MS (m/z, relative intensity): 40 (49), 41 (9), 42 (11), 43
(100), 44 (5), 52 (2), 59 (3), 72 (7), 73 (3), 101 (2), 110 (4), 165 (17,
Mþ-Me).
4.16. 2-(2, 2-Dimethyi-1, 3-dioxan-4-yl)butanedioic acid 1,4-
dimethyl ester (3aK-syn, anti)
Dimethyl maleate (1a-cis, 28.61 mg, 0.20 mmol) and DTBP
(14.93 mg, 0.10 mmol) in 2, 2-dimethyl-1,3-dioxane (2K, 10 mL).
Irradiation time: 3 h. NMR yield (CDCl3), 34% (syn/anti ¼ 21/13)
(conversion: 100%). Eluent for chromatography: hexane/ethyl ace-
tate (20/1 / 0/1).
3cJ-anti: 3.4 mg (9%); colorless oil; 1H-NMR (
d, CDCl3): 1.36 (s,
3H), 1.46 (s, 3H), 2.81 (dd, J ¼ 7.2, 17.2 Hz, 1 H), 2.87 (dd, J ¼ 5.2,
17.2 Hz, 1 H), 2.96 (ddd, J ¼ 5.2, 7.2, 7.8 Hz, 1 H), 4.03 (dd, J ¼ 3.6,
9.2 Hz, 1 H), 4.23e4.33 (m, 2 H) ppm. 13C-NMR (
d, CDCl3): 18.0, 24.8,
26.9, 33.2, 67.4, 74.0, 111.5, 115.2, 116.4 ppm. IR (KBr disk): 2988,
2937, 2250, 1456, 1423, 1375, 1259, 1215, 1151, 1059, 981, 840,
514 cmꢁ1. MS (m/z, relative intensity): 40 (4), 41 (10), 42 (12), 43
(100), 44 (6), 52 (2), 59 (3), 61 (3), 72 (7), 101 (3), 110 (4), 165 (16,
Mþ-Me).
3aK-syn: 4.91 mg (10%); colorless oil; 1H-NMR (
d, CDCl3):
1.2e1.48 (m, 1 H), 1.35 (s, 3 H), 1.44 (s, 3 H), 1.70 (dddd, J ¼ 5.6, 12.0,
12.4, 12.4 Hz, 1 H), 2.60 (dd, J ¼ 4.8, 17.2 Hz, 1 H), 2.75 (dd, J ¼ 10.0,
17.2 Hz, 1 H), 3.08 (ddd, J ¼ 4.8, 5.6, 10.0 Hz, 1 H), 3.68 (s, 3 H), 3.72
(s, 3 H), 3.84 (ddd, J ¼ 2.0, 5.6, 12.0 Hz, 1 H), 3.94 (ddd, J ¼ 2.8, 12.0,
12.0 Hz, 1 H), 4.20 (ddd, J ¼ 2.4, 5.6, 12.0 Hz, 1 H) ppm. 13C-NMR (
d
,
4.19. 3-(2-Methyl-1, 3-dioxolan-2-yl)propionic acid tert-butyl ester
(3dG)
CDCl3): 19.1, 27.2, 29.7, 31.1, 46.4, 51.8, 52.0, 59.6, 68.8, 98.7, 172.5,
172.6 ppm. IR (KBr disk): 2992, 2949, 2925, 2854, 1737, 1464, 1438,
1371, 1328, 1270, 1244, 1225, 1197, 1162, 1120, 1101, 1050, 1002, 970,
862, 847, 767, 524 cmꢁ1. MS (m/z, relative intensity): 41 (17), 43
(100), 55 (26), 57 (27), 58 (20), 59 (52), 67 (13), 71 (21), 93 (14), 115
(14), 125 (10), 139 (16), 153 (43), 171 (26), 245 (23), 260 (0.62, Mþ).
HRMS: m/z calcd. for C12H20O6 þ H: 261.1338; found: 261.1344.
tert-Butyl acrylate (1d, 25.43 mg, 0.20 mmol) and DTBP
(14.63 mg, 0.10 mmol) in 2-methyl-1, 3-dioxolane (2G, 10 mL).
Irradiation time: 0.5 h. NMR yield (CDCl3), 36% (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (20/1 / 0/1).
3dG: 13.45 mg (31%); colorless oil; 1H-NMR (
d
, CDCl3): 1.32 (s,
3 H), 1.44 (s, 9 H), 1.97 (t, J ¼ 7.8 Hz, 2 H), 2.31 (t, J ¼ 7.8, 2 H),
3.89e3.98 (m, 4 H) ppm. 13C-NMR (
, CDCl3): 24.0, 28.0, 30.3, 34.0,
3aK-anti: 2.03 mg (4%); colorless oil; 1H-NMR (
d, CDCl3): 1.34 (s,
3 H), 1.37e1.46 (m, 1 H), 1.42 (s, 3 H), 1.69 (dddd, J ¼ 5.2, 11.6, 12.4,
12.4 Hz, 1 H), 2.73 (d, J ¼ 7.2 Hz, 2 H), 2.90 (dt, J ¼ 7.2, 7.2 Hz, 1 H),
3.67 (s, 3 H), 3.72 (s, 3 H), 3.83 (ddd, J ¼ 1.6, 5.2, 12.0 Hz, 1 H), 3.94
(ddd, J ¼ 3.0, 12.0, 12.4 Hz, 1 H), 4.08 (ddd, J ¼ 2.8, 7.2, 11.6 Hz, 1 H)
d
64.7, 80.1, 109.3, 172.9 ppm. IR (KBr disk): 3440, 2979, 2932, 2883,
2678, 2370, 2321,1731,1478,1455,1391,1368,1311,1282,1255,1157,
1099, 1056, 977, 948, 866, 852, 805, 756, 650, 559, 526, 491,
439 cmꢁ1. MS (m/z, relative intensity): 41 (53), 43 (67), 57 (31), 87
(100), 99 (24), 143 (18), 145 (15), 216 (0.05, Mþ). HRMS: m/z calcd.
for C11H20O4 þ H: 217.1440; found: 217.1498.
ppm. 13C-NMR (
d, CDCl3): 19.1, 29.3, 29.7, 32.1, 47.3, 51.8, 52.0, 59.6,
69.0, 98.7, 172.7, 173.1 ppm. IR (KBr disk): 2993, 2953, 2925, 2871,
1737, 1438, 1381, 1338,1267, 1245, 1199, 1165, 1131, 1092, 1049, 1025,
1009, 969, 843 cmꢁ1. MS (m/z, relative intensity): 41 (18), 43 (100),
44 (24), 55 (27), 57 (29), 58 (19), 59 (57), 67 (12), 71 (22), 73 (11), 93
(14), 115 (14), 125 (12), 139 (17), 153 (47), 171 (29), 245 (25). HRMS:
m/z calcd. for C12H20O6 þ H: 261.1338; found: 261.1311.
4.20. 3-Methyl-3-(2-methyl-1, 3-dioxolan-2-yl)propanoic acid tert-
butyl ester (3eG)
tert-Butyl crotonate (1e, 28.76 mg, 0.20 mmol) and DTBP
(14.97 mg, 0.10 mmol) 2-methyl-1,3-dioxolane (2G, 10 mL). Irradi-
ation time: 0.5 h. NMR yield (CDCl3), 49% (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (20/1 / 0/1).
4.17. 2-(2-Methyl-1, 3-dioxolan-2-yl)butanedinitrile (3cG)
Fumaronitrile (1c-cis, 15.62 mg, 0.20 mmol) and DTBP
(14.77 mg, 0.10 mmol) in 2-methyl-1,3-dioxolane (2G, 10 mL).
Irradiation time: 0.5 h. NMR yield (CDCl3), 71% (conversion: 100%).
Eluent for chromatography: hexane/ethyl acetate (80/1 / 0/1).
3eG: 21.75 mg (47%); colorless oil; 1H-NMR (
d, CDCl3): 1.00 (d,
J ¼ 6.9 Hz, 3 H), 1.26 (s, 3 H), 1.45 (s, 9 H), 1.98 (dd, J ¼ 8.9, 14.9 Hz,
1 H), 2.19e2.33 (m, 1 H), 2.49 (dd, J ¼ 5.3, 14.9 Hz 1 H), 3.88e3.99
3cG: 23.40 mg (70%); colorless oil. 1H-NMR (
d, CDCl3): 1.51 (s,
(m, 4 H) ppm. 13C-NMR (
d, CDCl3): 15.3, 20.6, 28.1, 38.2, 38.5, 64.6,
3H), 2.79 (dd, J ¼ 8.0, 17.7 Hz, 1 H), 2.83 (dd, J ¼ 6.0, 17.7 Hz, 1 H),
64.7, 80.0, 111.4, 172.6 ppm. IR (KBr disk): 2979, 1730, 1458, 1368,
1296, 1256, 1154, 959, 872, 847, 760 cmꢁ1. MS (m/z, relative in-
tensity): 41 (24), 43 (43), 57 (14), 87 (100), 113 (12), 157 (10), 231
(0.01, Mþ). HRMS: m/z calcd. for C12H22O4: 230.1512; found:
230.1514.
3.21 (dd, J ¼ 6.0, 8.0 Hz, 1 H), 4.03e4.15 (m, 4 H) ppm. 13C-NMR (
d,
CDCl3): 16.5, 22.3, 38.1, 65.61, 65.63, 107.2, 116.1, 116.9 ppm. IR
(KBr): 3001, 2979, 2950, 2898, 2247, 1440, 1390, 1268, 1237, 1211,
1170, 1106, 1062, 1027, 950, 891, 793, 719, 652, 559 cmꢁ1. MS (m/z,
relative intensity): 40 (3), 41 (4), 42 (6), 43 (100), 44 (3), 45 (16), 51
(3), 52 (10), 53 (4), 54 (4), 66 (4), 79 (6), 80 (5), 87 (62), 88 (3), 93 (4),
07 (12), 151 (10). HRMS: m/z calcd. for C8H10O2N2 þ Na: 189.0640;
found: 189.0639.
4.21. 2-Isopropenylbutanedioic acid 1,4-dimethyl ester (3aL-a) [38]
and 2-isopropylbutanedioic acid 1,4-dimethyl ester (3aL-b). [39]
Dimethyl maleate (1a-cis, 30.02 mg, 0.21 mmol) and DTBP
(16.21 mg, 0.11 mmol) in isopropyl ether (2L, 10 mL). Irradiation
time: 3 h. NMR yield (CDCl3), 3aL-a: 30%, 3aL-b: 23% (conversion:
100%). Eluent for chromatography: hexane/CH2Cl2 (1/0 / 1/25 and
then 1/0 / 19/1). Only a part of 3aL-a was isolated by two chro-
matographic separations and 3aL-b was obtained as a mixture with
3aL-a.
4.18. 2-(2, 2-Dimethyl-1, 3-dioxolan-4-yl)butanedinitrile (3cJ-syn,
anti)
Fumaronitrile (1c-cis, 15.61 mg, 0.20 mmol) and DTBP
(14.76 mg, 0.10 mmol) in 2, 2-dimethyl-1, 3-dioxolane (2J, 10 mL).
Irradiation time: 2 h. NMR yield (CDCl3), 22% (syn/anti ¼ 12/10)
t
Please cite this article as: M. Hayakawa et al., Photochemical addition of cyclic ethers/acetals to olefins using BuOOtBu: Synthesis of masked
ketones/aldehydes and diols, Tetrahedron, https://doi.org/10.1016/j.tet.2020.131557

M. Hayakawa et al. / Tetrahedron xxx (xxxx) xxx
11
3aL-a: 8.4 mg (22%); colorless oil; 1H-NMR (
d, CDCl3): 1.76 (s,
Declaration of competing interest
3 H), 2.52 (dd, J ¼ 5.5, 16.5 Hz, 1 H), 2.95 (dd, J ¼ 9.6, 16.5 Hz, 1 H),
3.55 (dd, J ¼ 5.5, 9.6 Hz, 1 H), 3.68 (s, 3 H), 3.71 (s, 3H), 4.91 (d,
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
J ¼ 1.0 Hz, 1 H), 4.93 (dd, J ¼ 1.0, 1.5, 1 H), ppm. 13C-NMR (
d, CDCl3):
20.6, 35.1, 48.5, 51.8, 52.2, 114.3, 141.3, 172.1, 173.0 ppm. IR (KBr
disk): 3082, 2953, 2847, 1738, 1647, 1437, 1339, 1296, 1260, 1217,
1163, 1096, 1003, 964, 901, 847, 772, 559 cmꢁ1. MS (m/z, relative
intensity): 53 (27), 55 (100), 59 (61), 67 (56), 68 (23), 69 (51), 81
(13), 83 (66), 84 (46), 85 (86), 94 (16), 95 (42), 96 (14), 109 (14), 113
(26), 114 (18), 122 (24), 123 (28), 124 (31), 125 (13), 126 (20), 127
(29), 146 (42), 154 (42), 155 (98), 186 (Mþ, 6), 187 (Mþþ1, 11).
Acknowledgements
This work was supported by JSPS KAKENHI Grant Number
JP17K05953 and the Sasakawa Scientific Research Grant from The
Japan Science Society (M. H.). We thank Professor Masako Takada
for the use of her Gaussian system and Ms. Kaori Wada for NOESY
and ROESY measurements.
3aL-b: 13.8 mg (mixture with 3aL-a); 1H-NMR (
d, CDCl3): 0.92
(d, J ¼ 6.0 Hz, 3 H), 0.94 (d, J ¼ 6.0 Hz, 3 H), 1.93e2.04 (m, 1 H), 2.42
(ddd, J ¼ 8.7, 8.7, 12.8 Hz, 1 H), 2.68e2.78 (m, 2 H), 3.67 (s, 3 H), 3.70
(s, 3 H) ppm. 13C-NMR (
d, CDCl3): 19.6, 20.1, 30.1, 32.9, 47.4, 51.6,
Appendix A. Supplementary data
51.8, 172.9, 174.9 ppm. IR (mixture with 3aL-a) (KBr disk): 2953,
2916, 1738, 1437, 1373, 1348, 1260, 1194, 1163, 1115, 1020, 1005, 899,
849 cmꢁ1. MS (mixture with 3aL-a) (m/z, relative intensity): 45
(12), 54 (16), 55 (50), 59 (100), 67 (28), 68 (13), 69 (26), 83 (18), 84
(10), 85 (38), 87 (11), 94 (11), 95 (15), 97 (13), 101 (26), 113 (25), 114
(37), 115 (16), 122 (16),126 (13),146 (17),154 (26),155 (31), 157 (19),
188 (Mþ, 0.0), 189 (Mþþ1, 0.02).
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2020.131557.
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4.22. Hydrolysis of esters 3aA-syn and 3aA-anti
4.22.1. General procedure
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[33a,35]
3aA-syn (39.55 mg, 0.18 mmol) was hydrolyzed and purified to
3bA-syn (8.7 mg, 25%), white solid; 1H NMR (acetone-d6):
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d
¼ 1.65e1.77 (1H, m), 1.80e1.99 (3H, m), 2.45 (1H, dd, J ¼ 3.9,
16.8 Hz), 2.68 (1H, dd, J ¼ 10.3, 16.8 Hz), 3.00 (1H, ddd, J ¼ 3.9, 6.3,
10.3 Hz), 3.66 (1H, ddd, J ¼ 6.5, 7.7, 7.7 Hz), 3.82 (1H, ddd, J ¼ 6.5,
8.2, 8.2 Hz), 4.06 (1H, ddd, J ¼ 6.3, 6.5, 7.6 Hz), 10.8 (2H, br s) ppm.
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1703e1712;
13C NMR (acetone-d6):
d
¼ 26.3, 29.0, 32.6, 46.5, 68.6, 79.7, 173.4,
174.1 ppm. IR (KBr): 3437 (br), 3044 (br), 2984 (br), 2967 (br), 2930
(br), 2886 (br), 1773, 1699, 1437, 1408, 1314, 1275, 1254, 1219, 1192,
1138, 1114, 1070, 1020, 999, 941, 923, 841, 696, 667, 542, 444 cmꢁ1
.
MS, m/z (relative intensity): 40 (10), 41 (54), 42 (28), 43 (96), 44
(36), 45 (19), 53 (9), 55 (37), 57 (11), 67 (8), 69 (9), 71 (100), 97 (7),
111 (29), 114 (8), 125 (9), 129 (47), 143 (7), 188 (0.1, Mþ).
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d
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Please cite this article as: M. Hayakawa et al., Photochemical addition of cyclic ethers/acetals to olefins using BuOOtBu: Synthesis of masked
ketones/aldehydes and diols, Tetrahedron, https://doi.org/10.1016/j.tet.2020.131557

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