Abstract
We report for the very first time a continuous-flow route to perform the intramolecular cyclization of haloalkyl-substituted α-amino esters via memory of chirality (MoC), using lithium bis(trimethylsilyl)amine as a base and methyl N-(tert-butoxycarbonyl)-N-(3-chloropropyl)-D-alaninate as a model reactant. The various reaction parameters, such as temperature, residence time, reactant stoichiometry, or type and concentration of the base were optimized to maximize the yield of the cyclized product and its enantiomeric excess. At the conditions identified, the reaction was eventually scaled up, reaching a productivity of 11 g h−1. Compared to the standard batch protocols available in the literature, the use of a microreactor enables a better control of the exothermicity associated with the addition of the organolithium reagent to the reaction mixture, resulting in operations at more practical temperatures, with high enantiospecificity and full conversion of the reactive amino ester within a few seconds of residence time.

ᅟ
This is a preview of subscription content, access via your institution.







Abbreviations
- F 16 :
-
flow rate in mL min−1 of compound 16 in a solution of DMF
- F base :
-
flow rate in mL min−1 of the base solution
- T :
-
reaction temperature
- Boc :
-
tert-butyloxycarbonyl
- LC :
-
liquid chromatography
- GC :
-
gas chromatography
- MS :
-
mass spectrometry
- NMR :
-
nuclear magnetic resonance
- X :
-
conversion of 16
- ee :
-
enantiomeric excess
References
Park K-H, Kurth MJ (2002). Tetrahedron 58:8629
Kano T, Sakamoto R, Mii H, Wang Y-G, Maruoka K (2010). Tetrahedron 66:4900
Kawabata T, Yahiro K, Fuji K (1991). J. Am. Chem. Soc. 113:9694
Zhao H, Hsu DC, Carlier PR (2005). Synthesis 1:1
Seebach D, Naef R (1981). Helv. Chim. Acta 64:2704
Seebach D, Sting AR, Hoffmann M (1996). Angew. Chem. Int. Ed. 35:2708
Branca M, Gori D, Guillot R, Alezra V, Kouklovsky C (2008). J. Am. Chem. Soc. 130:5864
Schmalz H-G, de Konig CB, Bernicke D, Siegel S, Pfletschinger A (1999). Angew. Chem. Int. Ed. 38:1620
Buckmelter AJ, Kim AI, Rychnovsky SD (2000). J. Am. Chem. Soc. 122:9386
Giese B, Wettsein P, Stähelin C, Barbosa F, Neuburger M, Zenher M, Wessig P (1999). Angew. Chem. Int. Ed. 38:2586
Kolaczkowski L, Barnes DM (2007). Org. Lett. 9:3029
Hicks F, Hou Y, Langston M, McCarron A, O’Brien E, Ito T, Ma C, Matthews C, O’Bryan C, Provencal D, Zhao Y, Huang J, Yang Q, Heyang L, Johnson M, Sitang Y, Yuqiang L (2013). Org. Process. Res. Dev. 17:829
Macharia J, Wambua V, Hong Y, Harris L, Hirschi JS, Evans GB, Vetticatt MJ (2017). Angew. Chem. Int. Ed. 56:8756
Salmon AG, Kizer KW, Zeise L, Jackson RJ, Smith MT (1995). J. Toxicol. Clin. Toxicol. 33:115
Wu G, Huang M (2014). Org. Process. Res. Dev. 18:1192
Kawabata T, Kawakami S, Majumdar S (2003). J. Am. Chem. Soc. 125:13012
Kawabata T, Wirth T, Yahiro K, Suzuki H, Fuji K (1994). J. Am. Chem. Soc. 116:10809
Kawabata T, Matsuda S, Kawakami S, Monguchi D, Moriyama K (2006). J. Am. Chem. Soc. 128:15394
Kawabata T, Moriyama K, Kawakami S, Tsubaki K (2008). J. Am. Chem. Soc. 130:4153
Pastre JC, Browne DL, Ley SV (2013). Chem. Soc. Rev. 42:8849
Baumann M, Baxendale IR, Beilstein J (2015). Org. Chem. 11:1194
Vilé G, Richard-Bildstein S, Lhuillery A, Rueedi G (2018). ChemCatChem 10:3786–3794
Abele S, Höck S, Schmidt G, Funel J-A, Marti R (2012). Org. Process. Res. Dev. 16:1114
Amann F, Frank M, Rhodes M, Robinson A, Kesselgruber M, Abele S (2016). Org. Process. Res. Dev. 20:446
Kockmann N, Thenée P, Fleischer-Trebes C, Laudadio G, Noël T (2017). React. Chem. Eng. 2:258
Glasnov TN, Kappe CO (2011). Chem. Eur. J. 17:11956
Yoshida J, Takahashia Y, Nagaki A (2013). Chem. Commun. 49:9896
Yoshida J, Kim H, Nagaki A (2017). J. Flow. Chem. 7:60
For general methods to prepare 16, see: (i) Kachkovskyi G, Faderl C, Reiser O (2013). Adv. Synth. Catal. 355:2240; (ii) Anxionnat B, Robert B, George P, Ricci G, Perrin MA (2012). J. Org. Chem. 77:6087
The chiral analysis of 16 was performed by analyzing the starting material using the method reported in the Supporting Information, and comparing this with a racemic mixture containing both 16 and ent -16
Sapse AM, von Ragué Schleyer P (1995) Lithium Chemistry – a Theoretical and Experimental Overview. Wiley, New York, p 145
Hessel V, Kralisch D, Kockmann N, Noël T, Wang Q (2013). ChemSusChem 6:746
Wegner J, Ceylan S, Kirschning A (2012). Adv. Synth. Catal. 354:17
Fogler, H. Elements of chemical reaction engineering 1992, 2nd edition. Prentice Hall, Upper Saddle River
Singh R, Panda G (2013). RSC Adv. 3:19533
Acknowledgements
We are grateful to Dr. Simone Tortoioli for proof-reading the manuscript and for valuable comments. The authors would like to thank Julien Grimont for NMR support, as well as Claus Mueller and his team for analytical methods and chiral analyses. Finally, Dr. Thomas Weller is sincerely acknowledged for support and comments on the paper.
Author information
Authors and Affiliations
Corresponding author
Electronic supplementary material
ESM 1
(DOCX 407 kb)
Rights and permissions
About this article
Cite this article
Vilé, G., Schmidt, G., Richard-Bildstein, S. et al. Enantiospecific cyclization of methyl N-(tert-butoxycarbonyl)-N-(3-chloropropyl)-D-alaninate to 2-methylproline derivative via ‘memory of chirality’ in flow. J Flow Chem 9, 19–25 (2019). https://doi.org/10.1007/s41981-018-0022-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s41981-018-0022-5
Keywords
- Flow chemistry
- Asymmetric synthesis
- Cyclization
- Microreactors
- Memory of chirality