2,4-Dichloro-5-(1-o-carboranylmethyl)-6-methylpyrimidine: A Potential Synthon for 5-(1-o-Carboranylmethyl)pyrimidines

The synthesis of 2,4-dichloro-5-(1-o-carboranylmethyl)-6-methylpyrimidine is described. Synthetically, this novel o-carboranyl pyrimidine is approached from ethyl 2-acetyl-4-pentynoate through alkylation of ethyl acetoacetate with propargyl bromide and subsequent condensation with thiourea to yield 6-methyl-5-(2-propynyl)-2-thio-4(1H,3H)-pyrimidinone. Hydrolysis of the 2-thione and chlorination with POCl₃ gives 2,4-dichloro-6-methyl-5-(2-propynyl)pyrimidine. Gentle refluxing of this product with B₁₀H₁₄/CH₃CN in toluene yields the target, 2,4-dichloro-5-(1-o-carboranylmethyl)-6-methylpyrimidine, a potential synthon for a variety of 2,4-substituted 5-(1-o-carboranylmethyl)-6-methylpyrimidines and/or the corresponding nido-undecaborates.