Reaktionen von Malonsäurederivaten mit Dicyclohexylcarbodiimid

Abstract

Malonsäure (la) und monosubstituierte Malonsäure, z. B. 1 b, geben mit 2 mol Dicyclohexylcarbodiimid (2) die Barbiturate 3 a bzw. b. Die disubstituierte Malonsäure l c liefert primär das 1,3‐Oxazin 5. Die Umsetzung verläuft in zwei Stufen: Zuerst bildet sich ein 4gliedriges Anhydrid 12 das dann mit einem zweiten mol 2 über ein Zwischenprodukt 13 reagiert. Bei Phenylmalonsäure (6) ist je nach Lösungsmittel 7 oder 10 das Hauptprodukt.

Mechanistic Study on the Cleavage and Reorganization of C(sp3)H and CN Bonds in Carbodiimides: Synthesis of 1,2‐Dihydrothiopyrimidines and 2,3‐Dihydropyrimidinthiones through Four‐Component Coupling

“…The filtrate was concentrated under reduced pressure and the residue was purified by recrystallization in EtOH to give 3 . The data of compound 3 is consistent with that reported 17…”

“…Therefore, as an alternative, we tried to synthesize its oxygen‐analogue B‐ O , considering that oxygen and sulfur atoms are in the same chalcogen group with very similar properties. Thus, as given in Scheme , we synthesized the oxygen‐analogue precursor 3 through [2+2] cycloaddition of 2‐phenylmalonic acid with N , N′ ‐dicyclohexylcarbodiimide 17. We then carried out the base‐promoted reaction of 3 at different temperatures.…”

“…Thus, as given in Scheme 4, we synthesized the oxygen-analogue precursor 3 through [2+2] cycloaddition of 2-phenylmalonic acid with N,N'-dicyclohexylcarbodiimide. [17] We then carried out the base-promoted reaction of 3 at different temperatures. Compound 3 was treated with lithium diisopropylamide (LDA) in THF at À78 8C for 1 h to provide the four-membered anionic intermediate B-O, which was trapped with D 2 O and MeI.…”

“…Preparation of N-acyl 2,3-dihydropyrimidinthiones 9 through a new CÀN bond formation: Representative results for the formation of 9 through fourcomponent coupling of terminal alkynes, elemental sulfur, carbodiimides, and acid chlorides are summarized in Table 1 (entries [15][16][17][18][19]. The acyl group is regioselectively connected to the nitrogen atom of the S=CÀ N unit.…”

“…The data of compound 3 is consistent with that reported. [17] Compound 3: Isolated yield: 70 % (227 mg); colorless solid; 1 : d = 24.33, 24.51, 24.89, 25.07, 25.26, 30.06, 30.31, 33.78, 34.60, 51.65, 59.61, 62.00, 127.28, 127.84, 128.86, 132.05, 150.33, 167.87 1 mmol) was added dropwise at À78 8C to a stirred solution of 3 (1 mmol, 324 mg) in THF (10 mL). After stirring at À78 8C for 1 h, D 2 O (1 mmol) was added dropwise at RT to a stirred solution of the above reaction mixture.…”