[PDF] Visible-light mediated carbamoyl radical addition to heteroarenes

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Visible

Ashique Hussain Jatoi, Govind Goroba Pawar, Frédéric Robert, and Yannick Landais* 1

2 3 4

5

2N(C=O)X precursors (X = H,4,6 7 8 9..), (2) the

3

5,10 11

2

2S2O8 5 These conditions however

12 isible

13 and an hypervalent iodine reagent as an oxidant (Figure 1). This metal

Figure 1 N-

3a 2a and lepidine

1a as a model heteroaromatic base (Table 1). Photocatalyst 4CzIPN14

2 2 (PIFA) and BI3a

15

12 3a (entries 6

16 2Cl2

2Cl2

Table 1 Addition of oxamic acid 2b 1a.

222
222
22
22
+4 -22 22
22
22
22
22d
a Unless otherwise mentioned, all reactions were performed with 1a 2b b 3a 1H NMR with 1,3,5

3a. e Absence of blue LED.

2 1a 3a

3e). 3m, having benzylic

Scheme 1 1a. Oxamic acid scope.

Other heteroaromatic compounds were submitted to the optimal reaction conditions above, showing that the method is

17

3q, 3r 3s, only one was observed. Benzimidazole and benzothiazole were found to be competent

3x). A similar reactivity was observed for 4

3t in moderate yield. In these cases, the absence of extended aromatic systems probably

3)2benzene, but again not addition was

Scheme 2 1a.

4 2i, affording bis5

2i, suggesting that

4, the first amidation increasing the electron

17c 7 1a

6.

a The reaction was carried out with heteroaromatic bases 4, oxamic acid 2i, PC (1 mol%) and oxidant (1.5 eq.) in DCE (0.15 M) in a sealed tube. b The reacti

1a, oxamic acid 6, PC (1 mol%) and oxidant (1.5 eq.) in DCE (0.15 M) in a sealed tube.

Scheme 3

Finally, oxamic acids 8awere prepared from

t-t-

11 8a 1,

9a rac-8a, and

rac-9a 9a

9a with Lewis acids such as Eu(hfc)3 2CO3) led

9a

Scheme 4

12 III

II, itself issued from the hypoiodite species I, formed in situ

18 , would form , while returning

.+). Cleavage of the weak O

III o-

III IV, the oxidation of which

.+, generating cationic species V. Deprotonation of the latter and rearomatization would finally give the corresponding

17a,c

2) onto hereoarenes.4,17a

IV .+) would give the final protonated amide. This mechanism cannot be formally

ed out at this stage, although our conditions are much less acidic than those in Minisci's work (H2SO4).

In summary, we reported the addition, onto heteroaromatic bases, of carbamoyl radical species generated through a ͞metal-

free" photocatalyzed odžidatiǀe decarbodžylation of odžamic acids. This strategy allows a straightforward and enǀironmentally

benign carba N-

Notes and references

1 Chatgilialoglu, C.; Crich, D.; Komatsu, M.; Ryu, I. Chem.Rev. 99, 1991.

(a) Tetrahedron Lett., 1961, 2, 238; (b) J. Org. Chem., 1964, 29, 1855; (c) Tetrahedron, 1964, 20, 1843; (d) J. Org. Chem., 1966, 31, 4210; (e)

J. Org. Chem., 2014, 79, 8094; (f)

J. Org. Chem., 2015, 80, 3586; (g) Org. Lett., 2001, 3, 2085; (h) Org. Lett., 2001, 17, 3054; (i) J. Am. 127, (i) Chem. Commun. 2000, 2327; Org. Biomol. Chem.,

2, 421.

(a) Org. , 2015, 17, 346; (b) W. F. Petersen,

Org. Biomol. Chem., 2017, 15, 5831.

(a) Tetrahedron 41, 4157; Chem. Commun. 2002, 2496 J. Joseph, A. P. Antonchick, Topics Heterocycl. , 2018, 54, 93. (a) F. Minisci, F. Coppa and F. Fontana, J. Chem. Soc., Chem. (b)

J. Org. Chem., 1995, 60, 5430.

(a) Adv. Synth. Catal., 2011, 353, 3295; (b)

J. Org. Chem., 2008, 73, 4721; (c)

J. Chem. Soc., Chem. Commun., 1993, 1760; (d) Org. Lett., 2017, 19, 1060; (e) Chem. Sci., 2013, 4, 2690; (f) Chem. , 2011, 47, 6587. (a) Chem. , 2015, 51, 8345;

Chem. Eur. J., 2014, 20, 6505.

M. Sakamoto, M. Takahashi, T. Fujita, T. Nishio, I. Iida, and S.Watanabe, J. Org. Chem. 199560, 4683.

G. B. Gill, G. Pattenden and S. J. Reynolds, J. Chem. Soc., Perkin Trans. 1, 1994, 369. (a) Org. Biomol. Chem., 2016, 14, 7380; Org. ,19, 874; (c) Org. Lett., 2018, 20, 2172.

Y. Seki, K. Tanabe, D. Sasaki, Y. Sohma, K. Oisaki, M. Kanai, Angew Chem. Int. Ed. 2004, 53, 6501; (b)

Bioorg. Med. Chem. Lett.,19, 6192.

G. G. Pawar, F. Robert, E. Grau, H. Cramail, and Y. Landais, Chem. Commun., 2018, 54, 9337. For selected reviews on visible(a) C. K. Prier, D. A. Rankic and D. W. C. MacMillan,Chem. Rev.

2013, 113, 5322; (b) Chem. Soc. Rev., 2011, 40, 102; (c)

Chem. Rev., 2016, 116, 1007; Angew. Chem., Int. Ed., 2018, 57, 10034. H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, Nature, 2012, 492, 234. Y. Li, D. P. Hari, M. V. Vita, and J. Waser, Angew. Chem. Int. Ed. 2016, 55, 44. S. S. Fukuzumi, H. Kotani, K. Ohkubo, S. Ogo, N. V. Tkachenko,

J, 2004, 126, 1600.

For a discussion on the regioselectivity of radical additions to heteroarenes, see: (a) J.

1990, 27, 79;(b) F. O'Hara, D.G. Blackmond, P.S. Baran, J. Am. Chem. Soc. 2013, 135, 12122; (c)

Molecules, 2014, 19, 16190.

(a) Angew. Chem. Int. Ed., 2015, 54, 8374; (b) J. Am. , 2014, 136, 2280; (c) Angew. Chem. Int. Ed., 2015, 54, 1881; (d) ACS , 2016, 6, 4983; (e) Org. Lett., 2018, 20,quotesdbs_dbs29.pdfusesText_35

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