5-Cyclopentylidene-2,2-dimethyl-1,3-dioxane-4,6-dione synthesis

Yield:3968-30-7 34%

Reaction Conditions:

with piperidine;pyridine at 20; for 10 h;

Steps:

General Procedure for Condensation of Ketones with Meldrum’s Acid 5-Cyclopentylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (19a)

A 30-mL round-bottomed flask equipped with a magnetic stirring bar was charged with cyclopentanone(18a) (840 μL, 9.46 mmol), Meldrum’s acid (14) (1.50 g, 10.4 mmol), and anhydrous pyridine (9.46 mL).To the stirred resulting mixture was added piperidine (23) (87 μL, 0.95 mmol) at room temperature. Theresulting mixture was stirred at room temperature for 10 h, after which time TLC (hexanes/EtOAc = 3:1)indicated complete consumption of cyclopentanone (18a). The solvents of the resulting mixture wereazeotropically removed with toluene under reduced pressure to give a crude material, which was purifiedby flash silica gel column chromatography (hexanes/EtOAc = 3:1) to afford cyclopentylidene Meldrum’sacid 19a (679 mg, 3.23 mmol, 34%) as a white solid. Rf = 0.34 (hexanes/EtOAc = 3:1); Mp 78-80 °C(hexanes/EtOAc, white needle); IR (ATR, cm-1): 3018, 2969, 2876, 1718, 1597, 1392, 1299, 1274, 1216,1012, 920, 747; 1H NMR (400 MHz, CDCl3): d 3.22-3.12 (m, 4H), 1.89-1.79 (m, 4H), 1.71 (s, 6H); 13CNMR (100 MHz, CDCl3): d 194.4, 161.2, 110.8, 103.6, 38.8, 27.4, 25.5; HRMS (ESI-) calcd. for C11H13O4(M-H+), 209.0819; found, 209.0819

References:

Wakahara, Yuko;Noro, Takahiro;Sakata, Juri;Ueda, Hirofumi;Tokuyama, Hidetoshi [Heterocycles,2022,vol. 105,# 1,p. 438 - 460]