Aldehydes phosphorus nucleophile-carbonyl

Aminoalkyl and Related Acids. - Further development of the classical three component approach to aminoalkylphosphonates (the Kabachnik-Fields reaction) has been reported. The reaction of aldehydes, hydroxylamines and dimethyltrimethylsilyl phosphite using lithium perchlorate/diethyl ether as a catalyst gives N-trimethylsilyloxy-a-aminophosphonate derivatives. The catalytic activities of various lanthanide triflates as well as indium trichloride have been examined for the Kabachnik-Fields type reactions of aldehydes, amines and the phosphorus nucleophiles HP(0)(0Et)2 and P(OEt)3 in ionic liquids. TaCb-Si02 has been utilized as an efficient Lewis acid catalyst for the coupling of carbonyl compounds, aromatic amines and diethyl phosphite to produce a-... 

The first examples of diastereoselective additions of phosphorus nucleophiles to carbonyl compounds, applied to the synthesis of natural product analogs, involved carbohydrate-derived aldehydes and ketones. The achieved diastereoselectivity depended on the kind of sugar and protective groups used, and for the cyclic ketones usually higher diastereoselectivities were observed. In the aldose... 

The initial step of olefin formation is a nucleophilic addition of the negatively polarized ylide carbon center (see the resonance structure 1 above) to the carbonyl carbon center of an aldehyde or ketone. A betain 8 is thus formed, which can cyclize to give the oxaphosphetane 9 as an intermediate. The latter decomposes to yield a trisubstituted phosphine oxide 4—e.g. triphenylphosphine oxide (with R = Ph) and an alkene 3. The driving force for that reaction is the formation of the strong double bond between phosphorus and oxygen ... 

O The nucleophilic carbon atom of the phosphorus ylide adds to the carbonyl group of a ketone or aldehyde to give an alkoxide ion intermediate. 

This section deals with reactions that correspond to Pathway C, defined earlier (p. 64), that lead to formation of alkenes. The reactions discussed include those of phosphorus-stabilized nucleophiles (Wittig and related reactions), a a-silyl (Peterson reaction) and a-sulfonyl (Julia olefination) with aldehydes and ketones. These important rections can be used to convert a carbonyl group to an alkene by reaction with a carbon nucleophile. In each case, the addition step is followed by an elimination. 

The most useful methods for the formation of C-C bonds are based on the addition of C-nucleophiles to carbonyl compounds. Among the many variations of this basic scheme phosphorus ylides, capable of olefinating aldehydes or ketones in a single step, have proven to be exceedingly valuable reagents in organic synthesis. 

Nucleophilic Reactions of (Silylamino)phosphines. The reactions of (silylamino)phosphines with simple aldehydes and ketones proceed via nucleophilic attack by phosphorus followed by a [1,4] silyl migration from nitrogen to oxygen to yield new N-silylphosphinimines ( 3). With a,B-unsaturated carbonyl compounds, 1,4-addi-... 

Ylids can be isolated, but are usually used in reactions immediately they are formed. They are nucleophilic species that will attack the carbonyl groups of aldehydes or ketones, generating the four-membered ring oxaphosphetane intermediates. Oxaphosphetanes are unstable they undergo elimination to give an alkene (65% yield for this particular example) with a phosphine oxide as a byproduct. The phosphorus-oxygen double bond is extremely strong and it is this that drives the whole reaction forward. 

Phosphorus ylides are very important because of their use in the well-known Wittig reaction (1954) for the synthesis of alkenes. In the Wittig reaction, a phosphorus ylide (1) reacts with an aldehyde or ketone to yield the corresponding alkene (16) (Scheme 7). The reaction involves nucleophilic attack by the ylide (1) on the electrophilic carbonyl carbon atom to yield the betaine intermediate, which then collapses with elimination of the phosphine oxide and formation of the alkene (16). The driving force of the Wittig reaction is the production of the very strong phosphorus-oxygen double bond in the phosphine oxide (Scheme 7). 

Reactive ylides must be produced in the absence of oxygen and moisture, whereas stable ylides can be isolated as solid substances which are relatively insensitive to hydrolysis. Ylides which are stabilized by a carbonyl group generally only react with aldehydes if need be, they can be made to react with ketones under relatively drastic conditions [3]. In these cases, the Horner-Emmons reaction is the method of choice because of the greater nucleophilicity of the phosphonate carbanions in comparison to phosphorus ylides [6] (see Section E). 

This reaction was first reported by Pudovik in 1950. It is a base-promoted nucleophilic addition of organophosphorus anion to alkenes or alkynes and is generally known as the Pudovik reaction. Occasionally, it is also referred to as the Pudovik addition. In addition, since Abramov discovered a similar addition reaction of phosphorus compounds to carbonyl compounds at the same time, the addition of organophosphorus compounds to activated unsaturated systems (e.g., alkenes, alkynes, ketones, aldehydes,and... 

As in the case of the phosphorus ylides, it is believed that d-orbitals on the sulfur participate in bonding, resulting in stabilization of the carbanion site. On reaction with unconjugated ketones and aldehydes, dimethyloxosulfonium methylide gives epoxides. The reaction course involves carbonyl addition, followed by an intramolecular nucleophilic displacement. Several specific examples are given in... 

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