Ultrasonic-assisted synthesis of carbodiimides from N,N′-disubstituted thioureas and ureas

Abstract

A facile and efficient sonochemical method for the preparation of carbodiimides from their corresponding thioureas or ureas was described. Using Ph 3 P-I 2 combination in the presence of triethylamine, various diaryl, aryl-alkyl, as well as dialkyl substituted substrates could be converted into carbodiimides in good-to-excellent yields within short reaction times under mild conditions with simple experimental setup. Graphical abstract

RE[N(SiMe3)2]3-Catalyzed Guanylation/Cyclization of Amino Acid Esters and Carbodiimides

“…Amino acid esters, other than 1a , 1f , 1j , and 1k (bought from J&K Chemical), were prepared. Unsymmetrical carbodiimides 2b – g were synthesized following the previous work . Rare-earth metal catalysts YbCl 3 , (2,6- t Bu 2 C 6 H 3 ArO) 3 Yb, Yb­[N­(TMS) 2 ] 3 , and Yb­[N­(TMS) 2 ] 3 (μ-Cl)­Li­(THF) 3 were prepared according to literature methods, respectively.…”

“…Colorless solid, yield: 96%; 1 H NMR (400 MHz, CDCl 3 ): δ 8.08 (dd, J = 8.0, 1.3 Hz, 1H, ArH), 1H,ArH),7.31 (d,J = 8.1 Hz,1H,ArH),1H,ArH), 5.48 (s, 1H, NH), 4.40 (dd, J = 11.2, 5.1 Hz, 2H, CH), 1.55 (d, J = 7.2 Hz, 6H, CH 3 ), 1.31 (d, J = 6.2 Hz, 6H, CH 3 ) ppm. 13 C NMR (100 MHz, CDCl 3 ): δ 163. 4, 149.2, 149.1, 134.2, 127.3, 124.7, 122.4, 117.7, 43.8, 23.1, 20.5 6-Fluoro-3-isopropyl-2-(isopropylamino)quinazolin-4(3H)-one (3ba).…”

“…Colorless solid, yield: 66%; 1 H NMR (400 MHz, CDCl 3 ): δ 7.61 (dd, J = 8.8, 2.8 Hz, 1H, ArH), 7.29−7.06 (m, 2H, ArH), 5.30 (s, 1H, NH), 4.36 (d, J = 6.8 Hz, 1H, CH), 4.26 (dq, J = 13.1, 6.5 Hz, 1H, CH), 1.46 (d, J = 7.2 Hz, 6H, CH 3 ), 1.21 (d, J = 6.4 Hz, 6H, CH 3 ) ppm. 13 C NMR (100 MHz, CDCl 3 ): δ 162. 7, 162.6, 159.4, 157.0, 148.6, 145.8, 126.7, 126.6, 122.7, 122.4, 118.2, 118.1, 111.6, 111.3, 43.8, 22.9, 20.2 6-Chloro-3-isopropyl-2-(isopropylamino)quinazolin-4(3H)-one (3ca).…”

“…Colorless solid, yield: 76%; 1 H NMR (400 MHz, CDCl 3 ): δ 8.03 (d, J = 2.4 Hz, 1H, ArH), 7.46 (dd,J = 8.7,2.5 Hz,1H,ArH),1H,ArH),5.43 (s,1H,NH),2H,CH), 1.55 (d, J = 7.2 Hz, 6H, CH 3 ), 1.31 (d, J = 6.2 Hz, 6H, CH 3 ) ppm. 13 C NMR (100 MHz, CDCl 3 ): δ 162. 4, 149.2, 147.8, 134.5, 127.5, 126.5, 126.4, 118.6, 43.9, 23.1, 20.4 7.18 (d,J = 8.7 Hz,1H,ArH),5.43 (s,1H,NH),2H,CH), 1.54 (d, J = 7.2 Hz, 6H, CH 3 ), 1.30 (d, J = 6.3 Hz, 6H, CH 3 ) ppm.…”

“…4, 149.2, 147.8, 134.5, 127.5, 126.5, 126.4, 118.6, 43.9, 23.1, 20.4 7.18 (d,J = 8.7 Hz,1H,ArH),5.43 (s,1H,NH),2H,CH), 1.54 (d, J = 7.2 Hz, 6H, CH 3 ), 1.30 (d, J = 6.3 Hz, 6H, CH 3 ) ppm. 13 C NMR (100 MHz, CDCl 3 ): δ 162. 2, 149.3, 148.1, 137.2, 129.6, 126.7, 119.1, 114.8, 43.9, 23.0, 20.4 1.29−1.22 (m, 1H, CH 2 ) ppm.…”