C-C and C-N coupling reactions of an imidotitanium complex with isocyanides

Citation
A. Bashall et al., C-C and C-N coupling reactions of an imidotitanium complex with isocyanides, ORGANOMETAL, 19(23), 2000, pp. 4784-4794
Citations number
40
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
ORGANOMETALLICS
ISSN journal
02767333 → ACNP
Volume
19
Issue
23
Year of publication
2000
Pages
4784 - 4794
Database
ISI
SICI code
0276-7333(20001113)19:23<4784:CACCRO>2.0.ZU;2-H
Abstract
Reaction of the imidotitanium complex [(kappa (3)-N(2)Npy)Ti(=NtBu)(py)] (1 ) [N(2)Npy = (2-C5H4N)C(Me)(CH2NSiMe3)(2)] with 2,6-xylylisocyanide led to double insertion of the isocyanide into the imidotitanium bond and yielded the four-membered titanacycle [(kappa (3)-N(2)Npy)Ti{N(tBu)C(=N-2,6-Me2C6H3 )C(=N-2,6-C6H3Me2)}] (2), which was characterized by X-ray crystallography. While unreactive toward bulky arylisocyanides, 2 reacted with a whole seri es of isocyanides R-NC [R = Et, nBu, iPr, Cy, tBu, PhCH2, p-Tol, (R)-CH(CH3 )Ph] to give the iminoketene complexes [(kappa (3)-N(2)Npy)Ti{N(tBu)C[N(2,6 -Me2C6H3)]C(=C=NR)N(2,6-Me2C6H3)]-(R = Et, 3a; nBu, 3b; iPr, Sc; Cy, 3d; tB u, 3e; PhCH2, 3f; p-Tol, 3g; (R)-CH(CH3)Ph, 3h). Single-crystal X-ray struc ture analyses of 3d, 3f, and 3g were carried out, which established the coo rdination of an imidoylketeneimene fragment to the metal center. The reacti on of 1 with alkyl isocyanides bearing H atoms or to the NC group leads to a sequential coupling of 3 molar equiv of the isocyanide with the imido com plex, yielding metal-bonded diaminodihydropyrimidine derivatives [(kappa (3 )-N(2)Npy)Ti{N(tBu)[-C=NCH(R)N(CH2R)CHC . NCH2R}] (R = H, 4a; CH3, 4b; C3H7 , 4C; Ph, 4d) and [(kappa (3)-N(2)Npy)Ti{N(tBu)[-C=NCRR'N(CHRR')CHC-]NCHRR' }] (R,R' = C5H10, 5a; CH3,CH3, 5b; Ph,CH3, 5c). An X-ray diffraction study of 4a unambiguously established the structure of this type of organometalli c complex. These products are thought to be formed in a reaction sequence i nvolving intermediates that are analogous to the stable complexes 2 and 3a- h. The latter are then converted to the N;heterocycles via a diazahexatrien e generated through a 1,5-sigmatropic H-shift and the subsequent cyclizatio n to give the pyrimidine derivatives.