Synlett 2020; 31(07): 683-686
DOI: 10.1055/s-0039-1690793
letter
© Georg Thieme Verlag Stuttgart · New York

Stereoselective α-Tertiary Alkylation of N-(Arylacetyl)oxazolidinones

Eunjae Shim
,
Armen Zakarian
This work was supported by the National Institute of General Medical Sciences (R01 077379).
Further Information

Publication History

Received: 04 December 2019

Accepted after revision: 29 December 2019

Publication Date:
17 January 2020 (online)


Abstract

A method has been developed for the α-tertiary alkylation of zirconium enolates of N-(arylacetyl)oxazolidinones. This reaction directly installs an all-carbon quaternary center vicinal to a benzylic tertiary carbon in a highly diastereoselective manner.

Supporting Information

 
  • References and Notes


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  • 8 4-Benzyl-3-(3,3-dimethyl-2-phenylbutanoyl)-5,5-dimethyl-1,3-oxazolidin-2-one; Typical Procedure An oven-dried 4 mL vial, equipped with a magnetic stirrer bar, was charged with oxazolidinone 1 (129 mg, 0.4 mmol) and ZrCl4 (98 mg, 1.05 equiv) in a nitrogen-filled glovebox. CHCl3 (1.0 mL) was added, and the mixture was stirred at rt for 10 min. Et3N (0.17 mL, 3.0 equiv) was then added and stirring was continued at rt for 45 min. t-BuBr (67 μL, 1.5 equiv) and SnCl4 (50 μL, 1.1 equiv) were added sequentially, and the mixture was stirred for 4 h at rt. The vial was opened and 0.5 M aq HCl (2 mL) was added. The mixture was transferred to a separatory funnel by using CH2Cl2 (3 × 1 mL) and 0.5 M aq HCl (3 × 1 mL) to wash the vial. After the layers were separated, the aqueous layer was extracted with CH2Cl2 (3 × 5 mL). The combined organic layers were dried (Na2SO4), filtered, and concentrated in vacuo. The resulting crude product was purified by column chromatography (silica gel, 10% Et2O–hexanes) to give a white solid; yield: 0.117 g (77%, dr 50:1); [α]D 25 82.3 (c 1.00, CHCl3). 1H NMR (500 MHz, CDCl3): δ = 7.41–7.36 (m, 2 H), 7.33–7.21 (m, 8 H), 5.03 (s, 1 H), 4.46 (dd, J = 9.7, 3.9 Hz, 1 H), 3.22 (dd, J = 14.3, 3.8 Hz, 1 H), 2.90 (dd, J = 14.4, 9.7 Hz, 1 H), 1.27 (s, 3 H), 1.01 (s, 3 H), 1.00 (s, 3 H). 13C NMR (126 MHz, CDCl3): δ = 173.43, 152.32, 137.04, 135.70, 130.70, 129.04, 128.64, 127.72, 127.13, 126.72, 81.53, 63.91, 57.22, 35.51, 35.02, 28.02, 22.13. HRMS-ESI: m/z [M + Na]+ calcd for C24H29NNaO3: 402.2045; found: 402.2052.