Verkade S Bases

Strong and Hindered Bases in Organic Synthesis

Verkade's bases

Verkade's bases, football-shaped proazaphosphatrane molecules of type 1, are very strong bases due to the extraordinary stability of 2 when 1 reacts with a proton.

Due to the stability of the protonated form 2, Verkade's bases are about eight orders of magnitude stronger as a Lewis base than any amine known, including the prominently used DBU, DBN and Proton Sponge. (14795).

Applications: Verkade's bases have been successfully applied in a variety of organic reactions, such as alkylations, dehydrohalogenations, acylations,^[1] a variety of condensation and organometallic reactions for carbon-carbon bond formation.^[2] A second characteristic of the novel cage molecules of type 1 is their ability to act as a superior catalyst for a continuously widening range of reactions^[3-6] such as protecting alcohol groups with various silyl groups during multistep syntheses,^[4] trimerizing isocyanates to isocyanurates^[5] and the synthesis of alpha, beta-unsaturated nitriles.^[6].

Table 7. Verkade's bases
55,695-5	2,8,9-Triisopropyl-2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane 2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane,2,8,9-tris(1-methylethyl)] C15H33N4P Mr 304.3 [175845-21-3] 1g, 5g
56,588-1	2,8,9-Triisobutyl-2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane Purity ~97% C18H39N4P Mr 342.51 [331465-71-5] 1g, 5g

References

1. Arumugam S, McLeod D, Verkade JG. 1998. Use of the Nonionic Superbase P(MeNCH2CH2)3N in the Selective Monoalkylation of Active-Methylene Compounds. J. Org. Chem.. 63(11):3677-3679. https://doi.org/10.1021/jo972350i

2. D'Sa BA, Kisanga P, Verkade JG. 1998. Direct Synthesis of ?,?-Unsaturated Nitriles Catalyzed by Nonionic Superbases. J. Org. Chem.. 63(12):3961-3967. https://doi.org/10.1021/jo972343u

3. Kisanga P, D'S B, Verkade J. 1998. P(RNCH2CH2)3N-Catalyzed ?,?-Dimerization of Unsaturated Nitriles:  Formation of 2-Alkylidene-3-alkylglutaronitriles. J. Org. Chem.. 63(26):10057-10059. https://doi.org/10.1021/jo981513f

4. D'S BA, Verkade JG. 1996. P(MeNCH2CH2)3N:  An Efficient Silylation Catalyst. J. Am. Chem. Soc.. 118(50):12832-12833. https://doi.org/10.1021/ja961010w

5. Tang J, Verkade JG. 1993. [P(MeNCH2CH2)3N] as a Superior Catalyst for the Conversion of Isocyanates to Isocyanurates. Angew. Chem. Int. Ed. Engl.. 32(6):896-898. https://doi.org/10.1002/anie.199308961

6. Kisanga PB, Verkade JG. 1999. P(RNCH2CH2)3N:  An Efficient Promoter for the Nitroaldol (Henry) Reaction. J. Org. Chem.. 64(12):4298-4303. https://doi.org/10.1021/jo9818733