Acyclic a,a-disubstituted b-phosphonyl esters containing chiral alcoholic auxiliaries were efficiently prepared and evaluated for the lithium naphthalenide-mediated asymmetric reductive alkylation. Among which, the best diastereoselectivity was received from the substrates bearing a (-)-phenylmenthyl group in leading to alkylated esters with up to 83:17 dr. The diastereoselectivity is proven to be controlled by the p-facial differentiation created by the chiral ester as well as the geometry of tetrasubstituted enolates generated by the reductive cleavage of C-P bond.Our previous study demonstrated that the cyclic bphosphonyl esters derived from the Diels-Alder reaction of triethyl 2-phosphono-2-alkenoates underwent the facile dephosphonylation by treating with lithium naphthalenide Scheme I Gleason´s approach for asymmetric creation of quaternary carbons 532 www.jccs.wiley-vch.de HRMS-EI m/z [M]+ calcd for C 26 H 43 O 5 P 466.2848, found 466.2857. (1R,2S,5R)-2-(Diethoxy-phosphoryl)-2-methyl-pentanoic acid 2-isopropyl-5-methyl-cyclohexyl ester (2b)From 1b, the typical procedure of preparing 2a was followed by using iodopropane and iodomethane as the alkylating

Treatment of α,α-dialkyl triethyl β-phosphonyl esters with LiAlH 4 in CH 2 Cl 2 -THF caused the one-pot dephosphonylation and reduction to yield the corresponding primary alcohols bearing a controllable β secondary carbon center. Mechanistic study has revealed that the LiAlH 4 -induced dephosphonylation should occur first with the assistance of the carboxylate group, and the hydrogen source of the resultant new C-H bond is LiAlH 4 .The cleavage of a phosphonyl group is an important process in synthetic chemistry. 1 During the previous study on the Diels-Alder reaction of 2-phosphono-2-alkenoates, 2 we serendipitously discovered that treatment of phosphoryl ester 1 derived from the cycloaddition between triethyl 2-phosphonoacrylate and cyclopentadiene with lithium aluminum hydride (LiAlH 4 ) caused the one-pot dephosphonylation-reduction to afford endo-{bicyclo[2.2.1]hept-5-en-2-yl}methanol (2) 3,4 as an useful synthetic intermediate 5 (Scheme 1). This so far undisclosed result attracted our attention because the reactions of phosphonates with LiAlH 4 in ethereal solutions usually produce the corresponding primary phosphines (RPH 2 ). 6 A literature search revealed that the reductive dephosphonylation of the phosphonates bearing a β-carbonyl moiety is rare and difficult to be achieved in practice. 1,7 Among few documented methods, Oh's group once reported a dephosphonylating operation on β-keto phosphonates, which involved treating the metal enolates of these substrates with LiAlH 4 in THF followed by quenching the reaction mixture with aqueous H 2 SO 4 solution to yield dephosphonylated ketones. 8 For this transformation, the results from deuterium-labeled experiments suggest that the cleavage of the P-C bond is not caused by the attack of a hydride on the α-or γ-carbon atoms. However, the detailed mechanism of dephosphonylation has remained to be obscure. Apart from this, Amedjkouh's group reported a related methodology for transferring the cyclic β-iminophosphonates into amines by LiAlH 4 , and the dephosphonylation upon the reduction was proposed to occur via the rearrangement of a lithiated phosphonyl amide intermediate. 9 To our knowledge, the LiAlH 4 -mediated reductive dephosphonylation has never been reported on β-phosphonyl ester system. In this regard, we decided to carry out a close examination on the reaction in Scheme 1 for exploring a mechanistic rationale and a synthetic route to highly substituted primary alcohols.