A wide array of dibenzyl phosphonites are amenable as substrates in this enantioselective dealkylation, furnishing air-and moisture-stable chiral H-phosphinate products that can be purified by silica gel column chromatography (Fig. ). Various para-substituted phenylphosphonites underwent dealkylation with good yield and enantioselectivity (3a-3g), with lower enantioselectivity observed for highly electron-withdrawing substituents (3h-3j). Metasubstituted phenylphosphonites were dealkylated with comparable enantioselectivities to their para-substituted regioisomers (3k-3m). In contrast, steric volume at the ortho position of the phenyl group was deleterious for enantioselectivity-o-fluoro substitution decreased enantioselectivity from 90% (3f) to 73% ee (3n), whereas o-phenyl substitution ablated enantioselectivity (3o). Substrates bearing ortho-fused polyaromatic substituents, however, could be dealkylated with high enantioselectivity (3p and 3q). The method is also compatible with a variety of hetero-and poly-aromatic substituents (3r-3t and 3v), including acid-labile functional groups (N-Boc-protected indole, 3u). Phosphonites with non-aryl substituents such as isopropenyl (3w) and adamantyloxy (3x) underwent dealkylation with moderate levels of enantioselectivity while alkyl substituents such as cyclopropyl and methyl afforded low levels of enantioselectivity at 54% and 30% ee respectively (see Supplementary Materials, Section 3.1). The enantioselective dealkylation of 2a was performed successfully on a gram scale employing only 3 mol % 1g with high enantioselectivity (93% ee), yield (98%), and efficient catalyst recovery (95%). The substituents on the H-phosphinate products obtained through this enantioselective dealkylation are known to exhibit complementary reactivity as the proton and alkoxide groups on phosphorus are prone to substitution by electrophiles and nucleophiles, respectively . To highlight the synthetic utility of enantioenriched H-phosphinates, we explored the reactivity of (R)-benzyl phenylphosphinate 3a as an orthogonally bifunctionalizable P-stereogenic building block. We found it amenable to an array of stereospecific synthetic elaborations of the P-H moiety, followed by secondary derivatization of the P-OBn moiety (Fig. ). Building on established phospha-Mannich reactivity of phosphinates , we found that deprotonation with lithium phenoxide enabled 3a to participate in the Pudovik addition to Eschenmoser's salt , affording 20 α-amino phosphinate 5a. The benzyloxy group of 5a could subsequently be substituted in the presence of methyllithium, preserving enantioenrichment at phosphorus . We also explored a polarity reversal strategy in the context of the Atherton-Todd reaction , in which the nucleophilic P-H moiety was converted to electrophilic P-Cl then trapped with heteroatom-based nucleophiles. In this context, nucleophiles such as benzylamine and tyrosine could be employed to access phosphonate esters and phosphonamidates 7a/b with high yields and enantiospecificities. To investigate phosphoryl-radical-mediated reactivity, we adapted the lithium phenoxide conditions to a previously reported 1,6-coupling between H-phosphinates and benzoquinones , finding that O-phosphoryl hydroquinone derivative 8a was obtained with excellent stereospecificity. This result indicates that the 3a-derived phosphoryl radical possesses sufficient configurational stability in the absence of chiral control elements to engage in stereospecific reactions . Finally, 3a was subjected to a sulfuration-methylation sequence to afford phosphonothioate 9a with excellent enantiospecificity .