Traditional-Strong-and-Hindered-Bases


Vol. 3, No. 1
Strong and Hindered Bases in Organic Synthesis
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Introduction / Phosphazene Bases / Verkade's Superbases / Traditional bases
Preservation of Reagents / Aldrich Schlenk-Type Glassware

Traditional Strong and Hindered Bases

Not only do we offer you specialized bases, such as the phosphazene or Verkade's bases, but we are also able to offer you our traditional bases, such as DBU, DBN, n-BuLi etc (for an alphabetic list see Table 9, 10 and 11). These traditional strong and/or hindered bases are well known and frequently used tools in organic synthesis. Proton Sponge® (14795) is an interesting example.  This compound is an extremely strong base for a tertiary amine. Protonation releases the strain of the two amines, resulting in a so-called "Proton Sponge". Take a look at Table 8 for the basicity strength for some of our traditional bases.
 

Table 8. Basicity strength of some traditonal bases
Product Number Product Name MeCNpKBH+
90605 1,5,7-Triazabicyclo(4.4.0)dec-5-ene (TBD) 25.98
69440 7-Methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene (MTBD) 25.44
33481, 33482 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) 24.33
33471 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) 23.89
87844 1,1,3,3-Tetramethylguanidine (TMG) 23.3
22709 Quinuclidine 19.51
87900 2,2,6,6-Tetramethylpiperidine (TMP) 18.64
76850 Pempidine (PMP) 18.62
90780 Tributlyamine 18.09
90340 Triethylamine 18.46
33480 1,4-Diazabicyclo[2.2.2]octan (TED) 18.29
27690 Collidine 14.77
62760 2,6-Lutidine (2,6-Dimethylpyridine) 13.92
*Absolute values in acetonitrile. Data obtained from Prof. Dr. Schwesinger, University of Freiburg, Germany
 
The general strength of the traditional lithium bases follows the order:
LDA < MeLi < n-BuLi < sec-BuLi < tert-BuLi

Table 9. Amine-based traditional bases  
27690 Phosphazene base P2-t-Bu solution sym.-Collidine, 2,4,6-Trimethylpyridine, 2,4,6-Collidine puriss. p.a., ≥99.0% (GC)   C8H11N   Mr 121.8   108-75-8   100 ml, 500 ml
20615 2-tert-Butyl-1,1,3,3-tetramethyl-guanidine purum, ≥97.0% (GC)   C9H21N3   Mr 171.3   29166-72-1   5 ml, 25 ml
33482 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) 2,3,4,6,7,8,9,10-Octahydropyrimidol[1,2-a]azepine H. Oediger, et al., Synthesis 1972, 591; N. Ono et al., Bull. Chem. Soc. Jpn. 1978, 51, 2401;
C. G. Rao, Org. Prep. Proc. Intl. 1980, 12, 225; N. Ono et al., Bull. Chem. Soc. Jpn. 1979, 52 , 1716. puriss., ≥99.0% (GC)   C9H16N2   Mr 152.2   [6674-22-2]   50 ml, 250 ml, 1 l
33481 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) 2,3,4,6,7,8,9,10-Octahydropyrimidol[1,2-a]azepine purum, ≥98.0% (GC)   C9H16N2   Mr 152.2   [6674-22-2]   50 ml, 250 ml, 1 l
33471 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) Amidine base used for dehydrohalogenation reactions to olefins: H. Oediger, et al., Synthesis 1972, 591. purum, ≥98.0% (GC)   C7H12N2   Mr 124.2   [3001-72-7]   25 ml, 100 ml, 500 ml
33480 1,4-Diazabicyclo(2.2.2)octane (TED), Dabco, Triethylenediamine purum, ≥95% (NT)   C6H12N2   Mr 112.18   280-57-9   100 g, 500 g
36672 N,N-Dicyclohexylmethylamine purum, ≥97.0% (GC)   C13H25N   Mr 195.35   7560-83-0   250 ml, 1 l
31960 N,N-Diethylaniline, free of mono-compounds puriss. p.a., ≥99.5% (GC)   C10H15N   Mr 149.24   91-66-7   100 ml, 500 ml
38395 N,N-Diisopropyl-2-ethylbutylamine purum, ≥98.0% (GC)   C12H27N   Mr 185.35  200342-33-2   25 ml, 100 ml
38431 N,N-Diisopropylmethylamine purum, ≥98.0% (GC)   C7H17N   Mr 115.22   10342-97-9   10 ml, 50 ml
38438 N,N-Diisopropyl-3-pentylamine purum, ≥99.0% (GC)   C11H25N   Mr 171.33   68714-10-3  1 ml, 5 ml
39430 N,N-Dimethylaniline puriss. p.a., ≥99.5% (GC)   C8H11N   Mr 121.18   121-69-7   100 ml, 500 ml
34775 2,6-Di-tert-butyl-4-methylpyridine
A sterically hindered, non-nucleophilic base which distinguishes between Brvnsted (protonic) and Lewis acids. Enables the direct high-yield conversion of aldehydes and ketones to vinyl triflates. Synthesis 1980, 283; Org. Synth. 1990, 68, 138. Hindered base for the O-alkylation of carbohydrates with alkyl triflates: J. Arnarp, et al., Acta Chem. Scand. Ser. B 32, 4, 1978; J. M. Berry, L. D. Hall, Carbohydr. Res. 1976, 47, 307; M. G. Ambrose, A. W. Binkley, J. Org. Chem. 1983, 48, 674; Base for the conversion of carbonyls in vinyl triflates with triflic anhydrides; P. B. Stang, W. Treptow, Synthesis 1980, 283. M. E. Wright, S.R. Pulley, J. Org. Chem. 1989, 54, 2886; W. J. Scott, et al., Org. Synth. 1990, 68, 116. purum, ≥97.0% (GC)   C14H23N   Mr 205.3   [38222-83-2]   5 g, 25 g
03440 N-Ethyldiisopropylamine solution, H|nig's base, N,N-Diisopropylethylamine, Proton scavenger used in peptide coupling,1 enolboration,2 Pd(0)-catalyzed alkoxycarbonylation of allyl phosphates and acetates,3 and as a catalyst in vinyl sulfone synthesis.4 (1) J. Org. Chem. 1994, 59, 695. (2) ibid. 1993, 58, 7162. (3) ibid. 1993, 58, 1538, Synth. Commun. 1993, 23, 3073. Ref 4. purum, ≥98.0% (GC)  C8H19N   Mr 129.2   [7087-68-5]   50 ml, 250 ml, 1 l
62760 2,6-Lutidine, 2,6-Dimethylpyridine purum, ≥96% (GC)  C7H9N   Mr 107.16   108-48-5   100 ml, 500 ml
69440 7-Methyl-1,5,7-triazabicyclo(4.4.0)dec-5-ene (MTBD) 1,3,4,6,7,8-Hexahydro-1-methyl-2H-pyrimido[1,2-a]pyrimidine purum, ≥98.0% (GC)  C8H15N3   Mr 153.23   84030-20-6   5 ml, 25 ml
76830 3,3,6,9,9-Pentamethyl-2,10-diazabicyclo-(4.4.0)dec-1-ene (PMDBD) 1,2,3,4,4a,5,6,7-Octahydro-2,2,4a,7,7-pentamethylnaphthyridine purum, ≥% (GC)  C13H24N2    Mr 208.35   69340-58-5   1 g
76850 1,2,2,6,6-Pentamethylpiperidine (PMP), pempidine
One of the most strongly basic tertiary amines (sterically hindered and nonquaternizing): H. Z. Sommer et al., J. Org. Chem. 1971, 36, 824. purum, ≥99.0% (GC)   C10H21N   Mr 155.3   [79-55-0]   5 ml, 25 ml
90340 Triethylamine puriss. p.a., ≥99.5% (GC) C6H15N   Mr 101.19   121-44-8   250 ml, 1 l, 2.5 l
87844 1,1,3,3-Tetramethylguanidine (TMG) puriss., ≥99.0% (GC)   C5H13N3  Mr 115.18   80-70-6   50 ml, 250 ml
14795 N,N,N',N'-Tetramethyl-1,8-naphthalenediamine (Proton Sponge)
Very strong base with weak nucleophilic character due to steric effects. J. Chem. Soc., Perkin Trans. 2 1991, 857; R.W. Alder et al., Chem. Commun. 1968, 723; R. L. Benoit et al., Can. J. Chem. 1987, 65, 996. purum, ≥99.0% (NT)  C14H18N2  Mr 214.31  20734-58-1   10 g, 50 g
87900 2,2,6,6-Tetramethylpiperidine (TMP) purum, ≥97.0% (GC) C9H19N   Mr 141.26   768-66-1   10 ml, 50 ml
90603 1,5,7-Triazabicylco(4.4.0)dec-5-ene on polystyrene bound to polystyrene crosslinked with 2% DVB,
Polymer-supported, strong, hindered pentasubstituted guanidine base c(base): ~2.6 mmol/g resin   5 g, 25 g
90605 1,5,7-Triazabicyclo(4.4.0)dec-5-ene, 1,3,4,6,7,8-Hexahydro-2H-pyrimido[1,2-a]pyrimidine (TBD) purum, ≥98.0% (T)  C7H13N3   Mr 139.19   5807-14-7   10 g, 50 g
90780 Tributylamine puriss. p.a., ≥99.0% (GC)  C12H27N  Mr 185.36   102-82-9   100 ml, 500 ml
90850 2,4,6-Tri-tert-butylpyridine purum, ≥98.0% (CHN)  C17H29N   Mr 247.43  20336-15-6   1 g, 5 g
93438 Tris(trimethylsilyl)amine purum, ≥97.0% (GC) C9H27NSi3   Mr 233.58  1586-73-8   5 g, 25 g
22709 Quinuclidine purum, ≥95% (NT) C7H13N   Mr 111.19   100-76-5   5 g, 25 g

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Table 10. Lithium-based traditional bases
20160 Butyllithium solution, n-BuLi techn., ~1.6 M in hexane C4H9Li   Mr 64.06  [109-72-8]  100 ml, 500 ml
20164 Butyllithium solution, n-BuLi techn., ~2.5 M in toluene  C4H9Li  Mr 64.06 [109-72-8]  100 ml, 500 ml
20159 Butyllithium solution, n-BuLi purum, ~2.7 M in heptane C4H9Li   Mr 64.06   [109-72-8]   100 ml, 500 ml
20161 Butyllithium solution, n-BuLi purum, ~10 M in hexane  C4H9Li   Mr 64.06   [109-72-8]  100 ml
20185 sec-Butyllithium solution, sec-BuLi, Lithium-2-butanide purum, ~1.3 M in cyclohexane  C4H9Li   Mr 64.06   [598-30-1]   100 ml, 500 ml
94439 tert-Butyllithium solution, t-BuLi, lithium-2-methyl-2-propanide purum, 1.6-3.2 M in heptane  C4H9Li  Mr 64.06  [594-19-4]  100 ml
20190 tert-Butyllithium solution, t-BuLi, Lithium-2-methyl-2-propanide techn., ~1.5 M in pentane  C4H9Li  Mr 64.06  [594-19-4]  100 ml, 500 ml
53200 Hexyllithium solution purum, ~2.5 M in hexane   [21369-64-2]   100 ml, 500 ml
62491 Lithium diisopropylamide solution, LDA ~2 M in THF/heptane/ethylbenzene, liquid, brown A non-pyrophoric LDA-THF complex. Strong, sterical hindered base used for the formation of carbaniones: Aldrichimica Acta,1984 17, 80. Lithium diisopropylamide as a hydride donor: Majewski M.; Tetrahedron Lett. 1988 29, 4057-60. The "3 + 2 intramolecular cycloaddition reaction of azomethine ylides generated from benzylic N-oxides: Roussi G., Heterocycles 1990, 31, 1445. techn.  C6H14LiN  Mr 107.1  [4111-54-0]  100 ml, 500 ml
67740 Methyllithium solution, MeLi purum, ~5% in diethyl ether (~1.6 M)  CH3Li  Mr 21.98  [917-54-4]  25 ml, 100 ml
67737 Methyllithium solution, MeLi purum, ~1 M in cumene/THF (~1.6 M)  CH3Li  Mr 21.98  [917-54-4]  50 ml, 250 ml $
67741 Methyllithium lithium bromide complex solution
Nucleophilic methylating agent used in the synthesis of other methyl organometallics and in the preparation of methyl lactones from carboxylic acids. J. Am. Chem. Soc. 1979, 101, 1455. Handbook of Reagents for Organic Synthesis: Acidic and Basic Reagents; Reich, H. J., Rigby, J. H., Eds.; John Wiley & Sons: New York, 1999 (Z33,820-6). techn., ~1.5 M in diethyl ether  CH3LiBrLi  Mr 108.8  [917-54-4]  100 ml, 500 ml

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Table 11. Potassium-based traditional bases
60071 Potassium bis(trimethylsilyl)amide solution, Hexamethyldisilazane potassium solution
Sterically hindered base employed in selective cyclization: J. Org. Chem. 1993, 58, 6177, 6874. Also used in the preparation of lanthanide complexes: Organometallics 1993, 12, 2618, ibid. 1992, 11, 2003. ~0.5 M in toluene  C8H18KNSi2   Mr 199.5  [40949-94-8]  100 ml, 500 ml
60066 Potassium bis(trimethylsilyl)amide, Hexamethyldisilazane potassium salt purum, ≥95.0% (T)  C8H18KNSi2  Mr 199.5  [40949-94-8]  25 g, 100 g
60100 Potassium tert-butoxide techn., ≥94% (T)  C4H9KO  Mr 112.2  [865-47-4]  10 g, 100 g, 500 g
60098 Potassium tert-butoxide purum, ≥97.0% (T)  C4H9KO  Mr 112.2  [865-47-4]  100 g, 500 g
60103 Potassium tert-butoxide solution purum, ~1 M in tetrahydrofuran  C4H9KO  Mr 112.2  [865-47-4]  100 ml, 500 ml
60102 Potassium tert-butoxide solution techn., ~1 M in tert-butanol  C4H9KO  Mr 112.2  [865-47-4]  100 ml, 250 ml
71337 Sodium tert-butoxide purum, ≥97.0% (T)  C4H9KO   Mr 112.2  [865-48-5]  10 g, 100 g, 500 g