Aluminium alkyl complexes supported by imino-phosphanamide ligand as precursors for catalytic guanylation reactions of carbodiimides

Abstract

Three aluminium alkyl complexes, [κ2-{ImRNP(Ph)NDipp}AlMe2] (2a–2c), supported by unsymmetrical imino-phosphanamide were synthesised and utilised as competent precatalysts for the hydroamination of carbodiimides under ambient conditions.

Organoaluminum Catalyzed Guanylation and Hydroboration Reactions of Carbodiimides

“…Further, a lower catalyst amount decreases the product formation rate. No N−H ( 3 a ) addition in DIC was noticed in the absence of catalyst 1 at neat condition, similar to the reported literature (Table 1, Entry 10) [2m] . It was worthy to note that the catalyst ( 1 ) also displayed quantitative catalytic activity for N−H ( p ‐toluidine) addition in DIC under 1 mol% catalyst load at rt within 30 min (Table 1, Entry 1).…”

“…Similarly, under the standard reaction conditions, piperidine and morpholine resulted in 99% of guanidine products 7 c – 7 e with symmetrical diaryl CDIs (Ar−N=C=N−Ar, where Ar=2,6‐Me 2 −C 6 H 3 and 2,6‐Et 2 −C 6 H 3 ). The present CBG aluminum alkyl compounds are more robust catalysts than previously reported aluminum methyl complexes for guanylation reactions [2c,h, j–m] …”

“…In 2009, Xi′s research group [2h] introduced trimethyl aluminum reagent (AlMe 3 ) as pre‐catalysts for guanylation of carbodiimides with high yields in benzene (C 6 H 6 ). Subsequently Bergman, [2j] Wang, [2k] Mandal, ,[2l] and Chandrasekhar's [2m] research groups independently developed suitable organoaluminum complexes as effective catalysts for synthesizing substituted guanidines using amines and carbodiimides in solvents such as toluene or hexane (Figure 1).…”

N^Nvs.N^E (E = S or Se) coordination behavior of imino-phosphanamidinate chalcogenide ligands towards aluminum alkyls: efficient hydroboration catalysis of nitriles, alkynes, and alkenes

“…Furthermore, to isolate the end-product of the hydroboration reaction of organic nitriles, we treated the diborylamine products using aqueous HCl (0.05 M) at room temperature for two hours, which afforded the corresponding benzyl ammonium chlorides (Table 5, 9a-9e). All the products were characterized by 1 H and 13 C NMR spectroscopy (Fig. S98-S107 in the ESI †).…”

“…In view of this, we recently embarked on the development of new unsymmetrical N-P-N ligands which upon deprotonation function as monoanionic ligands akin to the amidinate or guanidinate ligands (Scheme 1). 12,13 We recognized that the phosphorus center of these ligands can itself participate in binding or can be oxidized to a P(V) center by the formation of the PvE bond (E = S or Se). In the latter scenario, the chalcogen motif can also be induced to bind along with a nitrogen center, and such complexes, particularly with Al(III), would be of interest in catalysis.…”