Rare Earth Compounds And Lewis Acid To Promote The Nh Bond Selective Activation

N-H bonds are among the most ubiquitous and inexpensive chemical linkages in nature, the direct conversion of N-H bond to N-C bond through insertion reactions is an efficient and economical strategy for fine chemical production. Although it has been reported that two unsaturated C-C fuctionality can diinsert into one N-H bond in the intramolecular hydroamination/cyclization, the direct diinsertion of C-X fuctionality into one N-H bond is unknown. On the other hand, there have been detailed studies on the reactions of the cumulative double bond molecules (X=C=Y) with organometallic compounds, indicating that both the C=X and the C=Y double bonds can participate in polar addition reactions. However, in most cases only single-addition products are isolated, and the sequential C=X and C=Y bi-addition processes are rarely observed. Therefore, we systematically investigated the selective diinsertion of isocyanate into N-H bond promoted by organolanthanides; furthermore, we also studied the synthesis and reactivity of the bridge amido-amidate lanthanide compounds, and achieved the subsequent addition reaction of two N-H bonds with one cumulene molecule. According to the mechanism of the latter reaction, a novel method has been established for construction of six-or five-nitrogen-containing heteroatom cycles. Collectively, thirty-nine new organolanthanide complexes are synthesized, among which thirty-six structures were determined through X-ray single crystal diffraction analysis. The main achievements are as follows:First, it has investigated the diinsertion reaction of isocyanates into the N-H bond of pyridylamido lanthanocene complexes. The results indicated that the substituted groups on isocyanates, cyclopentadiene ring, or pyridyl ring and the radii of the center rare earth metals all have no impact on the diinsertion reaction pattern. Moreover, the mechanism of the diinsertion reactions may be step by step mono-insertion process. Even when pyridylamido lanthanocene reacted with 2 equivalent isocyanate also to afford the diinserted products, however, the reaction of isocyanate with 2-pyridylamine only gives the mono-addition product. It was found that the chelating coordination of HMPA can prevent the second insertion. Furthermore, it has been proven that nPr2NH can abstract one PhNCO unit from the diinserted products to form organic urea nPr2NHCONHPh, representing one rare example of selective release of the functional group of ligands in organolanthanide chemistry. These phenomena indicate that the present diinsertion is reversible, and the petus may be the fluxion of the proton. The existence of the ancillary chelating ligand could help to achieve the diinsertion of isocyanates into N-H bonds promoted by organolanthanides, which may give some new ideas for the design of catalytic cycle.Second,{CpLn(μ-η2:η2-NHC6H4CONH)[μ3-η1:η1:η2-NHC6H4CONH]LnCp (HMPA)}2(Ln= Yb(3-1a), Er(3-1b) Y(3-1c)) were prepared by the protonolysis of Cp3Ln with equivalent o-aminobenzamide in toluene at room temperature, after reacting with equivalent HMPA, respectively. When Cp3Yb reacted with 0.5 equivalent o-aminobenzamide and subsequent with equivalent HMPA to give [Cp2Yb(HMPA)]2(μ-η2:η1-NHC6H4CONH) (3-2). Treatment of 3-1 with four equivalent PhNCO affords the unexpected containing dianonic quinazolinedione (Qo) ligand product{Cp2Ln[μ3-η2:η2:1-Qo]}3Ln(HMPA)2 (Ln= Yb(3-3a), Er(3-3b) Y(3-3c)), demonstrating that the neighboring anionic NH group of amidate participation could lead to unique isocyanate insertion reactivity. Two unsaturated C=N and C=O double bonds of isocyanate may undergo the subsequent addition with the dianionic amino-amidate ligand in the above process. However, when 3-1 reacted with diisopropylcarbodiimide to only give the monoinsertion products {Cp2Ln[μ-η3:η1-iPrNC(NHiPr)NC6H4CONH]}3Ln(HMPA)3 (Ln= Yb(3-4a), Er(3-4b), Y(3-4c)), indicating that carbodiimide only insert into one N-H bond of the bridge amido-amidate ligand. The single N-H bond addition product {CpLn[μ-η3:η2-OCNHC6H4NC(NHR)NR]}2 (R=iPr, Ln= Yb (3-5a), Er (3-5b), Y(3-5c); R= Cy, Ln= Yb (3-6a), Er (3-6b), Y(3-6c)) without HMPA can be obtained by in situ reaction. In addition,3-5 can be transformed into 3-4 in the presence of HMPA.Third, it describes the construction of six-and five-nitrogen-containing heterocycles from the functionalized amines with cumulene double bond molecules catalyzed by Lewis acid. The results showed that anhydrous InCl3 can catalyze not only o-aminobenzylamine with carbodiimides to afford 2-amino-3,4-dihydroquinazolines, but also o-aminophenol or o-aminothiophenol with carbodiimides to afford 2-aminobenzoxazoles and 2-aminobenzothiazoles, respectively. These reactions all gave good or high yields and better selectivity. Both the stability of the products and the basicity of the eliminated amines play important roles on the chemical selectivity. Moreover, the possible mechanism has been identified.