Lithiated amidines

They are very unstable and must be generated at temperatures ranging between —100 and —120 °C, whereas lithiated amidines 683 can be kept in solution at —78 to — 20 °C989. Lithiated isonitriles 684 are also very unstable species990. 

Other reactions involving compounds with [CpM(CO)3] moieties include the reaction of [CpMo(CO)3Na] with [MeN=C(Cl)Ph] in the presence of [NH4PF8] to afford (13), with some of (14) [thought to be a hydride addition product of (13)] as by-product, the reaction of CpMo(CO)3Cl with lithiated amidines to afford products of general formula (15), and the synthesis of [CpMCH(NR)a-... 

No heterocycle containing a C=N bond is as powerful a director as the oxazolines or tetrazoles described above, but their imidazoline analogues 132 direct well if deprotonated to the amidine equivalent 133 of a secondary amide anion (Scheme 61). Pyrazoles 134 also direct lithiation, but need protecting with a bulky Af-substituent to prevent nucleophilic attack by the base (Scheme 62). ... 

Imines (98) may be lithiated66 if (a) they have no other acidic protons a to C=N and (b) they are A-methyl imines or they have other activation towards a-lithiation. The N-allyl amidines 99, for example, give interesting chiral organolithiums 100 with BuLi.67... 

Lithiated cyclic enamines 691 " 5 996 and amidines 692989,997 have been prepared by deprotonation of the corresponding heterocycles with f-BuLi in THF at — 78 °C, being allowed to react with several electrophiles. This methodology has been applied to the synthesis of pyrrolidine and piperidine derived compounds, intermediates 691 and 692 acting in these cases not as acyllithium equivalents. 

Doubly fused imidazoles may be synthesized by trapping the benzyne formed by lithiation and loss of lithium fluoride from the amidine (106.6). By limiting the amount of t-butyllithium used to about two equivalents, monosubstitution of the intermediate with an electrophile (such as water or iodomethane) is possible. 

There have been a few reports on the simple route to enamidines offerred by the Peterson reaction. Lithiation of a-silyl amidines such as 66 with Bu Li and subsequent Peterson reaction with carbonyl compounds gives the corresponding enamidines 67 (Scheme 2.42) [106,107). The enamidines 67 are converted to the amines by treatment with sodium borohydride in ethanol under slightly acidic conditions. These entire homologation processes can be performed without purification of the enamidine intermediates 67. 

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