N,N-Diethyl-1-propynylamine1

[4231-35-0]  · C7H13N  · N,N-Diethyl-1-propynylamine  · (MW 111.19)

(for dehydrations;1b,2 synthesis of amino-furans3 and -amides,4 cyclobutadienes,5 cyclobutenes,6 cyclobutanones,7 vinylogous amides8)

Alternate Names: 1-(N,N-diethylamino)propyne; DAP.

Physical Data: colorless liquid; amine odor; bp 130-132 °C.

Solubility: sol MeCN, THF, CH2Cl2, toluene, ether, CCl4.

Preparative Methods: from commercially available 1-diethylamino-2-propyne,9,10 N,N-diethylpropanamide,11,12 miscellaneous methods.1d

Purification: by distillation under reduced pressure (bp 80-85 °C/100 mmHg).

Handling, Storage, and Precautions: reacts with H2O, CO2; slowly oxidizes in air/UV light. This reagent should be used in a fume hood.

Addition Reactions.

N,N-Diethyl-1-propynylamine (1) participates in many types of reactions with alkynes, alkenes, dienes, benzynes, and 1,3-dipoles, giving products that arise either by concerted or polar processes involving zwitterionic intermediates.1 Much of its chemistry may be explained by considering its resonance structures.

Reaction of (1) with electron-deficient alkenes such as a,b-unsaturated sulfones (eq 1),7 a,b-unsaturated nitriles (a-chloroacrylonitrile,13 1-cyanocyclopentene6), and trifluorochloroethylene14 gives cyclobutenes such as (2), (3), and (4) that can be converted into cyclobutanones.

In reactions with 1-alkynyl sulfones, the intermediate cyclobutadienes can be trapped as metal complexes or as Diels-Alder adducts (eq 2).5

A [2 + 2] reaction with a sulfene gives thiete 1,1-dioxide (5).15 Michael addition of (1) to electrophilic isoxazoles yields bicyclic adducts.16

1,3-Oxazin-6-ones and (1) provide pyridine derivatives by an inverse electron demand [4 + 2] cycloaddition-elimination reaction sequence (eq 3).17 Fused-bicyclic oxazinones behave similarly and have been converted into thienopyridines,18 quinolones,19 and quinolines.19 Pyridazinecarboxylates are converted either into 2-aminopyridines or into aniline derivatives with (1), depending on pyridazine ring carboxylate substitution patterns.20 2-Substituted pyrimidines and (1) give azetodiazocines by a series of reactions that include a formal [4 + 2] cycloaddition, 1,3-sigmatropic shift, [2 + 2] cycloaddition, and isomerization.21

Ring Interconversions and Expansions.

N,N-Diethyl-1-propynylamine has been used to convert heterocyclic systems into other heterocyclic or carbocyclic systems. Reactions occur by addition-elimination (eq 4)22 and dipolar addition (eq 5)23a pathways.

6-Oxo-1,3,4-oxadiazines are readily converted into substituted 2-pyrones (eq 6).24 Likewise, pyridines are derived from pyrimidines25 and 1,2,3-triazines.26 Oxathiadiazines give 1,2,6-thiadiazines on addition of (1).27

Many ring expansions have been reported with (1). They generally proceed through dipolar addition mechanisms. Depending on their substitution patterns, 1,2-diacylcyclopropenes give either aminofurans (eq 7) or aminocyclopentadienes.3

Thiophosphonic acid anhydrides and (1) give thiaphosphorinanes (eq 8).28 Thioazetidinones give 1,3-thiazines29 and 1,2-dithioles give thiopyrans on reaction with (1).23

Oxazolidinones and dioxolanones react with (1) via 1,7-dipolar intermediates to produce oxazepinones (eq 9) and dioxepinones.30

Acylation Reactions.

N,N-Diethyl-1-propynylamine reacts with carbonyl and carboxyl groups to give acylated products. The reaction pathway (stepwise or cycloaddition) depends upon substitution patterns and solvent polarity.1 a,b-Epoxy ketones and (1) give vinylogous epoxy amides (eq 10).8 Alkyl and aryl dithioaryl esters form (E)-a,b-unsaturated thioamides on reaction with (1) (eq 11).31 Acyclic and cyclic trithiocarbonates, as well as thiazolthiones, provide similar derivatives in good yields.31-33

Acylation of N-acylhydroxylamines by (1) provides an entry to a-aminoamides after deprotection (eq 12).4 Betaines also react with (1) to give triazinediones34 and pyrimidines.35

Acylations also occur with metal-coordinated thioaldehydes and thioketones to yield thioacrylamides36 and with N-acyl-S-alkyl(aryl)thiobenzimidates to give N-acylaza-1,3-butadienes.37

Reactions with Isocyanates and Ketenes.

Products derived from reactions of isocyanates or ketenes with (1) depend strongly on the electrophile structure. Cycloaddition occurs by oxygen attack on an intermediate ketiminium salt, followed by ring opening.1 Ketene and (1) give an allenecarboxamide (eq 13).38 With silicon-substituted ketenes, silylalkyne (6) is produced via silicon migration from an initially formed allenecarboxamide.39 Similarly, CO2 yields allene dicarboxamide (7) in a reaction with 2 equiv of (1).40 Isothiocyanates and (1) give a-sulfinylamidines via ring-opening of intermediate 1,2-dihydro-1,2-thiazetes.41

Dehydrations.

The title reagent has been used for carboxyl activation in the conversion of acids to anhydrides2 (ynamines are faster than carbodiimides or Ethoxyacetylene),1c acids and amines to amides,2 benzaldoximes to benzonitriles,42 and in peptide synthesis.43 Heterocyclic systems have been prepared by cyclizing o-diheteroaromatics, b-amino alcohols, and 1,2-diamines with (1).44

Miscellaneous Transformations.

Arenesulfenyl chlorides add to (1) to give (E)- and (Z)-2-arylthio-1-chloro-N,N-diethylenamines that can be cyclized to benzothiophenes with Zinc Chloride.45 Phosphinous halides add to N,N-diethyl-l-butynylamine to give phosphirenes.46


1. (a) Ficini, J. T 1976, 32, 1449. (b) Viehe, H. G. In Chemistry of Acetylenes; Viehe, H. G., Ed.; Dekker: New York, 1969; p 861. (c) Viehe, H. G. AG(E) 1967, 6, 767. (d) Sandler, S. R.; Karo, W. In Organic Functional Group Preparations, 2nd ed.; Academic: New York, 1986; Vol. 2, Chapter 5.
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Kenneth C. Caster

Union Carbide Corporation, South Charleston, WV, USA



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