Synthese eines Doppel-Carbodiphosphorans und seiner Vorstufen / Synthesis of a Double-Carbodiphosphorane and its Precursors
Abstract The reaction of 1,4-dibromobutane with bis(diphenylphospliino)methane (1) yields two products, one of which is identified as butane-1,4-bis[diphenyl(diphenylphosphinomethyl)-phosphonium bromide] (3 a). Transylidation of this bis-phosphonium salt using two equiv-alents of (CH3)3P = CH2 affords the bis-ylide [CH2CH2P(C6H5)2 = CH-P(C6H5)2]2 (4) in high yields. This conversion can be reversed on treatment of 4 with etheral HCl (to give 3b). Methylation of 4 with CH3I occurs at phosphorus, however, and produces the bis-semiylide salt (5), [CH2CH2P(C6H5)2CHP(C6H5)2CH3]22⊕ 2I⊖. Transylidation of 5 (again with (CH3)3P = CH2) leads to the bis-carbodiphosphorane (6), [CH2CH2P(C6H5)2 = C = P(C6H5)2CH3]2. All compounds were characterized by elemental and detailed NMR analyses. The second product of the above quaternisation reaction is a cyclic bis-phosphonium salt (2) with a seven-membered ring structure.