Substituted triazines and pyrimidines from 1,3,5-triazine and a lithium amidinate, alkyl- or 1-azaallyl

Treatment of 1,3,5-triazine 1 with an alkyllithium LiR [R=a Me, b Bu-n, c B u-t, d Ph, e CH2TMS, f CH(TMS)(2) or g Si(TMS)(3)(THF)(3)] yielded the appr opriate 1:1 addition product 2a-2g, which upon hydrolysis gave the correspo nding mono-substituted dihydro-1,3,5-triazine H=NC(H)NC(H)(R)NCH 3a-3g. H-1 NMR spectral data showed that the 1,4-dihydrotriazine 3f in toluene-d(8) w as in equilibrium with its 1,2-dihydro tautomer. Heating 3f with EtOH or H2 O in an acidic medium led to the facile cleavage of a C-Si bond and the for mation of EtOTMS or (TMS)(2)O, respectively. The C-13 and N-15 NMR spectral data are compared with those obtained by B3LYP/6-31+G* computations on the model compound NC(H)NCH2NCH. Treatment of 1 with the lithium amidinate [Li {N(TMS)C(Ph)NTMS}](2) or with 1-azaallyllithium [Li{N(TMS)C(Ph)C(H)TMS}(tme n)], [Li{N(TMS)C(Bu-t)C(H)TMS}](2) or [Li{N(TMS)C(Ph)C(TMS)(2)}(THF)(2)] yi elded 2-phenyltriazine 5, 4-phenylpyrimidine 6, 4-tert-butylpyrimidine 9 or , in poor yield, the new 4-phenyl-5-trimethylsilylpyrimidine 7, respectivel y. In the case of 1 and [Li{N(TMS)C(Bu-t)C(H)TMS}](2) an intermediate was i solated-the thermally unstable [Li{N(TMS)C(H)NC(H)NC(H)C(H)C(Bu-t)NTMS}](n) 8. A pathway is proposed involving the 1,4-addition of the lithium compoun d to 1,3,5-triazine 1, followed by a 1,3-trimethylsilyl shift, ring-opening and the formation of a new C-C or C-N bond to form the appropriate aromati c heterocycle.