Amides to Esters

Although the aminolysis of esters to amides is auseful synthetic operation, usually it presents some disadvantages in terms of drastic reaction conditions, long reaction times or strong alkali metal as catalyst, which are usually not compatible with other functional groups in the molecule [6]. For this reason, enzymatic aminolysis of carboxylic acid derivatives offers a clean and ecological way for the preparation of different kind of amines and amides in a regio-, chemo-, and enantioselective manner. 

Tin reagents such as Sn[N(TMS)2]2 in the presence of an amine can also be use to convert an ester to an amide. This reagent can also be used to convert p-amino esters to P-lactams. The ester-to-amide conversion has also been accomplished electrochemically, by passing electric current in the cathodic compartment. 

CONVERSION OF ESTERS TO AMIDES WITH DIMETHYLALUMINUM AMIDES N,JV-I>IMETHYLCYCLOHEXANECARBOXAMIDE... 

Another method for converting esters to amides involves aluminum amides, which can be prepared from trimethylaluminum and the amine. These reagents convert esters directly to amides at room temperature.142... 

Ethyl diphenylphosphinite, 131 Thionyl chloride, 297 to anhydrides Tetracyanoethylene, 289 of esters to amides... 

AmidesThese reagents are prepared by reaction of A1(CH3)3 in tolugne with I lie hydrochloride salts of NH3, H2NCH3, and HN(CH3)2. They are easier to prepare Ihun dimethylaluminum amides (8, 182), but they are equally suitable for conversion of esters to amides. 

A [3+2] cycloaddition of fV-3-thymine-substituted enamine 64 with ethoxycarbonyl nitrile oxide, generated in situ from ethyl chloro(hydroxyimino)acetate, gave the dihydroisoxazole 65. Subsequent aromatization and ester-to-amide... 

Yang D, Kwon M, Jang Y et al (2010) A convenient and efficient synthesis of C-carbamoyl-1,2,3-triazoles from alkyl bromide by a one-pot sequential addition conversion of ester to amide using Zr(Ot-Bu)4. Tetrahedron Lett 51 3691-3695... 

These have been prepared by various combinations of straightforward steps including ester to amide conversion, alcohol protection, direct reduction of the ester or amide to the aldehyde group, and reduction of the ester to the alcohol followed by reoxidation to the aldehyde. The sensitivity of the (5)-propanals to epimeriza-tion has been of paramount concern. One of the best procedures which avoids racemization and has been run on a preparative scale is noted (eq 2). ... 

D1BAL-H-HNR R -HC1 complexes for efficient conversion of lactones and esters to amides. Tetrahedron Lett. 2001 42 73. 

The conversion of carboxylic esters to amides is a useful reaction, and unsubstituted, A-substituted, and A,A-disubstituted amides can be prepared this way from the appropriate amine.Both R and R can be alkyl or aryl, but an especially... 

Levin, J. i., Turos, E., Weinreb, S. M. An aiternative procedure for the aiuminum-mediated conversion of esters to amides. Synth. Common. 1982, 12, 989-993. 

Smith, L. A., Wang, W. B., Barneii-Curty, C., Roskamp, E, J. Conversion of esters to amides with amino halo stannylenes. Syn/eff 1993, 850-852. 

Huang, P.-Q., Zheng, X., Deng, X.-M. DIBAL-H-H2NR and DIBAL-H-HNR R HCI complexes for efficient conversion of lactones and esters to amides. Tetrahedron Lett. 2001,42, 9039-9041. 

Conversions of Esters to Amides 442 ArC02R —> ArCONH2 Carboxylic Acids Amides to Acids 415 ArCONR2 -> ArC02H and Derivatives ... 

Amides. Conversion of esters to amides in a solvent-free process uses microwave heating with solid t-BuOK. Oxidative decyanation of a-aminonitriles derived from aldehydes with r-BuOK in DMSO also afford amides. ... 

Amides and lactams. Conversion of acids and esters to amides is quite easy in the presence of [(Me3Si)2N]2Sn. This method is also applicable to ring closure of fi-amino esters to give /3-lactams. ... 

The change from ester to amide (procaine — procainamide) has already been illustrated above as an example of classical isosterism. Similarly the lactone ring of the muscarinic agonist pilocarpine was changed into various, still active... 

You should by now understand weU that the reaction goes from ester to amide rather than the other way round, because NH3 is a better nucleophile than MeOH and NHj is a worse leaving group than MeO". 

Draw the tetrahedral intermediate expected when ethoxide reacts with N, AT-dimethylbutanamide and then draw the tetrahedral intermediate formed when dimethylamide (MegN ) reacts with ethyl butanoate. Compare these structures and suggest which reaction is likely to proceed to amide to ester, or ester to amide. 

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