Chiral chelate ligands based on a neopentane framework; Introducing indenyl and fluorenyl donor groups

The neopentane-derived functionalized oxetane O(CH2)(2)C(CH3)(CH2OMs), 1, r eacts with indenyllithium (LiInd) or fluorenyllithium (LiFlu) to produce th e derivatives O(CH2)(2)C(CH3)(CH2R) (R = indenyl, fluorenyl), 2. The oxetan e ring of 2 undergoes nucleophilic ring-opening by reaction with LiPR'(2) t o give the chiral chelate ligands (HOCH2)(CH3)C(CH2R)(CH2PR'(2)) (R = inden yl, fluorenyl), 5. Nucleophilic ring-opening by LiInd or LiFlu is possible too, resulting in the functionalized ansa-Cp ligands (HOCH2)(CH3)C(CH2R)(CH 2R') (R, R' = indenyl, fluorenyl), 12. Electrophilic ring-opening of 2 with HBr to give (HOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, fluorenyl), 3, is als o possible. The alcohol function of 3 may be activated directly, whereas ac tivation of this group in 5 is only possible after BH, protection of the ph osphane function. The mesylates (MsOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, f luorenyl), 4, undergo, under basic conditions, spiro cyclization to produce spirocyclobutane derivatives 9 with the alpha-carbons of the five-membered cycles acting as the spiro centres. Substitution of the mesylate group of 4 by PR2 nucleophiles is therefore not possible. Ansa-Cp derivative (MsOCH2 )(CH3)C(CH(2)Ind)(CH(2)Flu), 12c also reacts with LiPPh2 with spiro cycliza tion to produce 9d, instead of giving the substitution product. Tripodal li gands (CH3)C(CH2R)(CHPPh2)(2) (R = indenyl, fluorenyl), 11, are accessible by the reaction of (MsOCH2)(CH3)C(CH2PPh2)(2) with LiInd or LiFlu. All comp ounds are fully characterized by the usual spectroscopic and analytical tec hniques including single-crystal X-ray analyses in several cases.