The discovery and use of silylated phosphorus reagents in this reaction represented a methodological advance. Selective silyl group transfer occurs in mixed reagents, and cleavage of the resulting silicon-oxygen bonds can often be accomplished hydrolytically, providing access to α-hydroxy derivatives. Alkylation of α-siloxy products provides a convenient route to otherwise difficult to access α-alkoxy phosphorus compounds. They can function as acyl anion equivalents when deprotonated, and give ketones after elimination under basic conditions. Simple ketones and aldehydes readily undergo addition of phosphites at the carbonyl carbon. In one interesting application, addition to ketenes gives products identical to the Arbuzov reaction of acid halides. α,β-Unsaturated ketones and aldehydes also undergo the reaction. Dienyl carbonyl substrates can experience 1,6-addition, as in the example below. Imines can also undergo the reaction (Pudovik reaction), affording α-alkylamino phosphonates. Primary amines can be produced only after acidic hydrolysis of an intermediate "tert"-butylamine; the use of unsubstituted imines requires very harsh conditions and gives low yields. The α-hydroxy alkylphosphonates produced by this method can be used for additional transformations. The original carbonyl carbon is acidified by its proximity to the phosphonate group. Deprotonation at this position generates a masked acyl anion, as the phosphonate functionality can be removed after the anion reacts. Phosphonate anions can undergo alkylation and olefination (the Horner-Wadsworth-Emmons reaction). When α-amino alkylphosphonates are employed in olefination, the resulting enamines can be hydrolyzed to ketones. Addition to unsaturated carbonyl compounds and deprotonation affords homoenolate equivalents. Silylated phosphite reagents are some of the most efficient for the production of α-hydroxyphosphonates. However, a few other methods exist to make these compounds. For instance, the phosphate-phosphonate rearrangement gives α-hydroxyphosphonates via a three-membered cyclic intermediate. Generally, phosphorus addition reactions are operationally simple. Solutions of reagents in polar (acetonitrile, ethanol, "tert"-butanol) and non-polar (benzene) solvents may be used.