1-N-Boc-4-Piperidinecarboxylic acid methyl ester → 4-(6,7-Dimethoxy-quinazolin-4-yl)-piperidine-1,4-dicarboxylic acid 1-tert-butyl ester 4-methyl ester

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Reaction Steps

To a mixture of piperidine-1,4-dicarboxylic acid 1-tert-butyl ester 4-methyl ester (17.1 g, 70.5 mmol), as prepared in the previous step, and 4-chloro-6,7-dimethoxyquinazoline (15.0 g, 67.0 mmol) (Oakwood Products, Inc.) immersed in a −78° C. bath was added 1.08 M LiHMDS/THF (71 mL, 77 mmol) in ˜20 mL portions under argon via syringe along the sides of the flask (to allow cooling of the hindered base before reaction with the ester). Following completion of LiHMDS/THF addition, the reaction was allowed to sit in the −78° C. bath for 2-3 min before removing the cold bath and allowing the mixture to stir with gradual warming to rt. After 18 h stirring at rt, and an additional 2 d sitting at rt, the mixture was quenched with 0.5 M NaH2PO4 (150 mL) and extracted with DCM (1×150 mL and 1×100 mL). The organic layers were combined, dried (Na2SO4), and concentrated under reduced pressure to provide the crude title compound as a translucent yellow oil that was used in the next step without further purification (33 g, “114%” crude yield). A small sample was purified by flash chromatography (1:1 hex/EtOAc) for characterization. 1H-NMR (400 MHz, CDCl3) δ 9.11 (s, 1H), 7.34 (s, 1H), 7.29 (s, 1H), 4.05 (s, 3H), 3.96 (s, 3H), 3.76-3.67 (m, 2H), 3.62-3.49 (m, 2H), 3.61 (s, 3H), 2.50-2.36 (br s, 4H), 1.46 (s, 9H). LC/MS (ESI): calcd mass 431.2, found 432.2 (MH)+.

Provenance & Evidence