A greener synthetic protocol for the preparation of carbodiimide

Three asymmetric guanidinato metal complexes: Synthesis, crystal structures and their use as pre-catalysts in the Meerwein–Ponndorf–Verley reduction

“…MeLi (1.6 M solution in hexane; Alfa Aesar), n-BuLi (2.0 M solution in hexane; Alfa Aesar) and AlMe 3 (2.0 M solution in hexane; Alfa Aesar) were obtained commercially and used as received. ArN@C@NC 6 H 5 (Ar = 2,6-Me 2 C 6 H 3 ) was prepared according to the literature procedures [21]. Diethylamine, aromatic and aliphatic aldehydes were dried over MgSO 4 and redistilled before use.…”

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

“…As summarized in Table 3, all the reported reactions toward the synthesis of N,N 0 -dicyclohexylcarbodiimide (3l) were rather sluggish requiring harsh conditions or long reaction times. A related system using iodine alone in the dehydrosulfurization of 1,3-dicyclohexylthiourea (entry 7) gave no conversion [14]. In comparison with other reported procedures, our method (entry 8) provided rapid access to carbodiimide 3l in satisfactory yield using simple and low-cost reagents.…”

“…Some examples included thermolysis-decarboxylation of isocyanates [5], dehydration of ureas [6][7][8][9][10][11], dehydrosulfurization of thioureas [8,[12][13][14][15][16][17], rearrangements of amidoximes [18,19], as well as metal-catalyzed direct condensation of an amine with an isonitrile [20,21]. Nevertheless, there are still some limitations associated with some of the existing methods including the use of expensive or highly toxic reagents, long reaction times, harsh reaction conditions, and/or limited substrate scope.…”

Novel Tandem Reaction for the Synthesis of N′‐Substituted 2‐Imino‐1,3‐oxazolidines from Vicinal (sec‐ or tert‐)Amino Alcohol of Desosamine

“…In this sense, a recently published "green" protocol describing carbodiimide preparation from thioureas using only iodine and triethylamine as reagents attracted our attention. [17] Because we used iodine and a base for the 3Ј-N-demethylation of macrolides (see Scheme 1), we reasoned that the formation of NЈ-substituted 2-imino-1,3-oxazolidines on desosamine could also be achieved from non-demethylated 14-and 15-membered antibacterial macrolides 1-3.…”