Darzens synthesis

The aza-Darzens reaction is analogous to the Darzens synthesis of epoxides (see Section 1.2.3.2) but employs imines in the place of aldehydes (Scheme 1.27). 

Barbier-Wieland degradation Boudroux-Chichibabin synthesis Bouveault aldehyde synthesis Darzens synthesis Friedel-Crafts Reaction Gatterman-Koch reaction Grignard reaction Reformatsky reaction Saytzeff reaction Ullmann coupling reaction Wiirtz coupling reaction Wiirtz-Fittig reaction... 

The Darzens synthesis of glycidic esters by condensation of carbonyl compounds with a-haloesters is an important and useful method" that has been extended in phosphorus chemistry. Unquestionably, the most general and perhaps most widely employed method for the synthesis of dialkyl 1,2-epoxyalkylphosphonates involves the reaction of dialkyl chloromethylphosphonates with carbonyl compounds. These synthetically useful phosphonates are readily obtained by standard alcoholysis of chloromethylphosphonic dichloride under anhydrous conditions. The latter is obtained in up to 67% yield from phosphorus trichloride and paraformaldehyde at 250°C. Several variations on the preparation of dialkyl 1,2-epoxyalkylphosphonates from dialkyl chloromethylphosphonates and different carbonyl partners have been reported. The conditions for generating the a-metallated dialkyl chloromethylphosphonates were found to be critical because of their notorious instability. 

Modified Darzens reaction. The original Darzens synthesis of u./3-unxaturated ketones3 involved the addition of acid chlorides to cyclohexenes in the presence of aluminum chloride or stannic chloride followed by dehydrohalogenation. For example, the addition of acetyl chloride to cyclohexene affords l-acetyl-2-chlorocyclohexane, which on dehydrohalogenation (dimethylaniline) gives methyl cyclohexenyl ketone. 

A procedure has been developed which extends the Darzens synthesis to the preparation of aziridine esters and amides (equation 29). Reaction of benzalaniline (80) and ethyl chloroacetate (in BuKDK/DME) results in the formation of the trans-aziridine (82a) in 29% yield analysis of the crude reaction mixture showed no more than 10% of the isomeric cis adduct (83a). Similarly, condensation of 2-chloro-N,N-diethylacetamide and (80) affords aziridines (82b) and (83b) in 65% yield. However, in this case the cis isomer predominates ( 90 10, cis trans). The formation of (83a R = OEt) as the major product is consistent with the overlap control model suggested by Zimmerman. Apparently, the decreased stability of the amide (81b) enolate relative to the ester (81a) enolate causes ki (cyclization) to become greater than k (addition Scheme 19) it follows that the stereochemical outcome is determined in the initial aldol step, and steric arguments are advanced to explain this outcome. 

Darzens synthesis of glycidic thiol esters. Standard conditions for the Dar-zens reaction of a-halo esters use sodium alkoxides as the base and the corre-... 

Darvon alcohol, 184-186 Darzens synthesis, 258, 340 DATMP, 164-165 Daunomycinone, 456 Debromination, 459 Decahydro-2,4,7-metheno-l 77-cyclo-penta(ajpentaIene-3-ol, 299 Decarboalkylation, 128 Decarbonylation, 91-92 Decarboxylation, 128... 

Cyclization of 2-benzylpent-4-enoic acid (a-benzyl-a-allylacetic acid) and related compounds 1 to corresponding 1,2,3,4-tetrahydronaphthalene (tetralin) derivatives 2, catalyzed by a strong acid, has been called Darzens synthesis of tetralin derivatives. The reaction formally falls into the category of a cycloisomerization reaction of alkenyl-substituted arenes. 

The Darzens synthesis [66-68] involves the condensation of aldehydes or ketones with ethyl chloroacetate in the presence of sodium amide or ethoxide to give a,)9-epoxy esters in one step. Aromatic ketones and aldehydes as well as aliphatic ketones give good yields. Yields from aliphatic aldehydes, however, are poor. 

Dakin oxidation 13, 183 15, 279 Darzens-Glaisen reaction 12, 847 Darzens synthesis of unsatd. ketones 11, 902... 

Aluminum chloride dimethylaniline Darzens synthesis of a,j -ethyleneketones s. 11, 902... 

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