10.1002/anie.201809115
Angewandte Chemie International Edition
COMMUNICATION
1989, 89, 863; c) P. R. Blakemore, Comprehensive Organic Synthesis,
2nd ed.; Vol. 1; G. A. Molander, P. Knochel, Eds.; Elsevier: Oxford,
2014, 516.
that di-substituted phosphorus ylides 9c and 9d successfully
participated in the reaction (entries 4 and 5). The reaction with g-
butyrolactone phosphorus ylide 9e was slower, and required
more forcing conditions (entry 6). Amide-stabilized phosphorus
ylide 9f was also amenable to the reaction (entry 7).
[2]
For recent examples of hydrofunctionalization of unactivated alkenes
under visible-light irradiation, see: a) D. J. Wilger, N. J. Gesmundo, D.
A. Nicewicz, Chem. Sci. 2013, 4, 3160; b) S. Mizuta, S. Verhoog, K. M.
Engle, T. Khotavivattana, M. O’Duill, K. Wheelhouse, G. Rassias, M.
Médebielle, V. Gouverneur, J. Am. Chem. Soc. 2013, 135, 2505; c) A.
J. Musacchio, B. C. Lainhart, X. Zhang, S. G. Naguib, T. C. Sherwood,
R. R. Knowles, Science 2017, 355, 727; d) A. J. Boyington, M.-L. Y.
Riu, N. T. Jui, J. Am. Chem. Soc. 2017, 139, 6582; e) H. Wang, N. T.
Jui, J. Am. Chem. Soc. 2018, 140, 163; f) Q. Zhu, D. E. Graff, R. R.
Knowles, J. Am. Chem. Soc. 2018, 140, 741. For a review, see: g) K. A.
Margrey, D. A. Nicewicz, Acc. Chem. Res. 2016, 49, 1997.
It was possible to convert the (alkoxycarbonyl)methyl group
into
a methyl group and a benzyl group via an N-
hydroxyphthalimide ester[18] (Scheme 2). After the reaction of 1a
with 2, the crude product 3a was directly hydrolyzed to 6-
phenylhexanoic acid (11). Carbodiimide-mediated condensation
with N-hydroxyphthal-imide (NHPI) afforded the ester 12. The
following reductive photodecarboxylation[19] afforded 1-
phenylpentane (13). On the other hand, nickel-catalyzed
decarboxylative cross-coupling of 12 with iodobenzene gave
1,5-diphenylpentane (14).[20] These sequential procedures allow
formal 1,2-hydromethylation[21] and 1,2-hydrobenzylation of
unactivated alkenes in an anti-Markovnikov manner.
[3]
For reviews, see: a) J. M. R. Narayanam, C. R. J. Stephenson, Chem.
Soc. Rev. 2011, 40, 102; b) K. L. Skubi, T. R. Blum, T. P. Yoon, Chem.
Rev. 2016, 116, 10035; c) N. A. Romero, D. A. Nicewicz, Chem. Rev.
2016, 116, 10075; d) J. Twilton, C. Le, P. Zhang, M. H. Shaw, R. W.
Evans, D. W. C. MacMillan, Nat. Rev. Chem. 2017, 1, 52; e) L. Marzo,
S. K. Pagire, O. Reiser, B. König, Angew. Chem. Int. Ed. 2018, 57,
10034; Angew. Chem. 2018, 130, 10188.
[4]
For photocatalytic reactions using gem-difluorinated phosphonium salts
as the precursors of (alkoxycarbonyl)difluoromethyl radical species,
see: a) Q.-Y. Lin, X.-H. Xu, K. Zhang, F.-L. Qing, Angew. Chem. Int. Ed.
2016, 55, 1479; Angew. Chem. 2016, 128, 1501; b) L. I. Panferova, A.
V. Tsymbal, V. V. Levin, M. I. Struchkova, A. D. Dilman, Org. Lett. 2016,
18, 996; c) Q.-Y. Lin, Y. Ran, X.-H. Xu, F.-L. Qing, Org. Lett. 2016, 18,
2419; d) Y. Ran, Q.-Y. Lin, X.-H. Xu, F.-L. Qing, J. Org. Chem. 2016,
81, 7001. See also: e) W. Yu, X.-H. Xu, F.-L. Qing, Org. Lett. 2016, 18,
5130.
Ph
i) fac-Ir(ppy)3
1a
C6F5SH
ii) KOH
Ph
OH
( )
2
[3a]
+
EtOH/H2O
ascorbic acid
DME/H2O (1:1)
RT, blue LEDs
O
2 (2.0 equiv)
11
iv-a)
Ru(bpy)3Cl2
6H2O
BNAH, t-BuSH
Ph
Me
iii)
( )
2
THF/H2O (7:3)
RT, blue LEDs
NHPI
DIC
[5]
For examples of photocatalytic atom transfer radical addition (ATRA)
reactions using an (alkoxycarbonyl)methyl radical species, see: a) J. D.
Nguyen, J. W. Tucker, M. D. Konieczynska, C. R. J. Stephenson, J.
Am. Chem. Soc. 2011, 133, 4160; b) C.-J. Wallentin, J. D. Nguyen, P.
Finkbeiner, C. R. J. Stephenson, J. Am. Chem. Soc. 2012, 134, 8875;
c) E. Arceo, E. Montroni, P. Melchiorre, Angew. Chem. Int. Ed. 2014,
53, 12064; Angew. Chem. 2014, 126, 12260; d) X.-J. Tang, W. R.
Dolbier, Jr. Angew. Chem. Int. Ed. 2015, 54, 4246; Angew. Chem.
2015, 127, 4320; e) G. Magagnano, A. Gualandi, M. Marchini, L.
Mengozzi, P. Ceroni, P. G. Cozzi, Chem. Commun. 2017, 53, 1591; f)
J. Cheng, Y. Cheng, J. Xie, C. Zhu, Org. Lett. 2017, 19, 6452. For a
recent review, see: g) T. Courant, G. Masson, J. Org. Chem. 2016, 81,
6945.
13
Ph
ONPhth
( )
40% (GC, 4 steps)
2
iv-b)
PhI
O
DMAP
DCM
12
(dtbbpy)NiBr2
Ph
( )
Ph
2
Zn, DMA, RT
14
41% (4 steps)
Scheme 2. Formal 1,2-hydromethylation and 1,2-hydrobenzylation of
unactivated alkenes.
In summary, we have developed the hydro[(alkoxycarbonyl)-
methylation] reaction of alkenes. The substrate scope is broad
and the reaction conditions allow a variety of functional groups.
These features will make this reaction extremely useful for
synthesizing elongated aliphatic esters from alkenes.
[6]
For examples of photocatalytic ATRA-type reactions, see: a) H. Yi, X.
Zhang, C. Qin, Z. Liao, J. Liu, A. Lei, Adv. Synth. Catal. 2014, 356,
2873; b) N. Esumi, K. Suzuki, Y. Nishimoto, M. Yasuda, Org. Lett. 2016,
18, 5704; c) M. Silvi, C. Sandford, V. K. Aggarwal, J. Am. Chem. Soc.
2017, 139, 5736; d) Y.-Y. Liu, X.-Y. Yu, J.-R. Chen, M.-M. Qiao, X. Qi,
D.-Q. Shi, W.-J. Xiao, Angew. Chem. Int. Ed. 2017, 56, 9527; Angew.
Chem. 2017, 129, 9655; e) I. Triandafillidi, M. G. Kokotou, C. G.
Kokotos, Org. Lett. 2018, 20, 36.
Acknowledgements
We thank Dr. Y. Nagata (Kyoto Univ.), Dr. A. Shimizu (Osaka
Univ.), and Dr. T. Nokami (Tottori Univ.) for their kind help in a
fluorescence quenching analysis and an electrochemical
analysis. We also thank Mr. S. Miyakawa (Kyoto Univ.) for
reproducibility testing. This work was supported by JSPS
KAKENHI [Scientific Research (S) (15H05756) and (C)
(16K05694)] and JST [ACT-C (JPMJCR12Z9)]. Y.F. and J.N.
thank the JSPS for Young Scientists for a Research Fellowship.
[7]
[8]
[9]
For examples of reductive ATRA-type reactions, see: a) S. Sumino, A.
Fusano, I. Ryu, Org. Lett. 2013, 15, 2826. See also: b) M. Nakajima, Q.
Lefebvre, M. Rueping, Chem. Commun. 2014, 50, 3619; c) C. Yu, N.
Iqbal, S. Park, E. J. Cho, Chem. Commun. 2014, 50, 12884; d) S.
Sumino, M. Uno, T. Fukuyama, I. Ryu, M. Matsuura, A. Yamamoto, Y.
Kishikawa, J. Org. Chem. 2017, 82, 5469.
a) T. Hamada, A. Nishida, O. Yonemitsu, J. Am. Chem. Soc. 1986, 108,
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Chem. Int. Ed. 2018, 57, 2469; Angew. Chem. 2018, 130, 2494.
When 3-phenylpropyl 2-bromoacetate was used instead of the ylide 2
under the same conditions as Eq. (1), the bromo-adduct was mainly
formed (67% NMR yield). See the supporting information (Table S1).
Keywords: alkenes • ascorbic acid • photocatalysis •
phosphorus ylides • radical reactions
[1]
For a seminal report, see: a) G. Wittig, W. Haag, Chem. Ber. 1955, 88,
1654. For reviews, see: b) B. E. Maryanoff, A. B. Reitz, Chem. Rev.
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