A versatile synthon for chemoselective N-acylation reagents, 2-fluoro- N-mesylaniline

Abstract

References

1. Chemoselective N-acylation reagents: (a) H. A. Staab and G. Walther, Angew. Chem., 1960, 72, 35; (b) T. Kunieda, T. Higuchi, Y. Abe and M. Hirobe, Tetrahedron Lett., 1982, 23, 1159; (c) A. Husson, R. Besselievre and H.-P. Husson, Tetrahedron Lett., 1983, 24, 1031; (d) T. Kunieda, T. Higuchi, Y. Abe and M. Hirobe, Chem. Pharm. Bull., 1984, 32, 2174; (e) A. V. Joshua and J. R. Scott, Tetrahedron Lett., 1984, 25, 5725; (f) Y. Nagao, K. Seno, K. Kawabata, T. Miyasaka, S. Takao and E. Fujita, Chem. Pharm. Bull., 1984, 32, 2687; (g) S.-I. Murahashi, T. Naota and E. Saito, J. Am. Chem. Soc., 1986, 108, 7846; (h) S.-I. Murahashi, T. Naota and N. Nakajima, Chem. Lett., 1987, 879; (i) Y. Kikugawa, K. Mitsui, T. Sakamoto, M. Kawase and H. Tamiya, Tetrahedron Lett., 1990, 31, 243; (j) T. Keumi, M. Shimada, T. Morita and H. Kitajima, Bull. Chem. Soc. Jpn., 1990, 63, 2252; (k) N. Akikusa, K. Mitsui, T. Sakamoto and Y. Kikugawa, Synthesis, 1992, 1058; (l) A. R. Katritzky and H. X. Chang, Synthesis, 1995, 62, 503; (m) M. C. O'Sullivan and D. M. Dalrymple, Tetrahedron Lett., 1995, 36, 3451; (n) D. Xu, K. Prasad, O. Repic and T. J. Blacklock, Tetrahedron Lett., 1995, 36, 7357; (o) R. S. Atkinson, E. Barker and M. J. Sutcliffe, Chem. Commun., 1996, 1051; (p) A. R. Katritzky, B. Yang and D. Semenzin, J. Org. Chem., 1997, 62, 726; (q) I. S. Blagbrough and A. Geall, Tetrahedron Lett., 1998, 39, 439.
2. (a) Y. Murakami, K. Kondo, K. Miki, Y. Akiyama, T. Watanabe and Y. Yokoyama, Tetrahedron Lett., 1997, 38, 3751; (b) K. Kondo and Y. Murakami, Chem. Pharm. Bull., 1998, 46, 1217; (c) enantioselective N-acetylation: K. Kondo, T. Kurosaki and Y. Murakami, Synlett, 1998, 725.
3. Preparation of diacylanilines 2 with BuLi–R ²COCl (R ² = BnO, cyclohexyl, t-butyl) was also unsuccessful .
4. N-Acetyl and benzoyl- N-trifluoromethanesulfonylanilines have been shown to behave as acylating reagents: J. B. Hendrickson and R. Bergeron, Tetrahedron Lett., 1973, 4607 However, preparation of N-benzyloxycarbonyl- N-trifluoromethanesulfonylaniline was unsuccessful .
5. The selectivity in the acylation of a 1∶1 mixture of a less hindered amine and a hindered amine was also investigated with 4b and 8b, respectively. The observed selectivity in the acylation with 4b and 8b was superior to the currently used reagents, as shown in Table 4 below
   Table 4 Competition acylation

   			Yield (%)	Selectivity ^a
   Entry	Reagent	Conditions	13+ 14	( 13∶ 14)
   a Determined by ^1H NMR analysis.
   1	4b	THF, rt, 18 h	90	8∶1
   2	BnOCOCl	Et 3N, THF, 0 °C, 1 h	92	3∶1
   3	8b	THF, 0 °C, 48 h	89	10∶1
   4	Bz 2O	THF, 0 °C, 1 h	92	5∶1
   5	BzCN	CH 2Cl 2, 0 °C, 12 h	97	5∶1
   6	Bz 2NOMe	THF, 0 °C, 12 h	88	3∶1

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6. Preparation of 4b: to a stirred solution of 3b (1.89 g, 10.0 mmol) in pyridine (25.0 mL) was gradually added ZCl (5.71 mL, 40.0 mmol) at 0 °C. The mixture was stirred for 1 h at rt. After usual work-up, purification by silica gel column chromatography (10% EtOAc in benzene) and subsequent recrystallization (benzene–hexane) afforded 4b (2.91 g, 90%) as colorless needles, mp 97–100 °C; v_max(Nujol)/cm ⁻¹ 1737, 1497, 1346 and 1155; δ_H(CDCl ₃) 3.42 (s, 3 H), 5.21 (s, 2 H), 7.12–7.42 (m, 9 H); m/ z (EI-MS) 323 (M ⁺), 244, 91 (bp). A satisfactory CHN analysis ± 0.3% was obtained. Other compounds 5b–8b were prepared in an analogous fashion. .