Schwesinger base

O Donnell and coworkers conducted this type of Michael addition with the organic-soluble, Schwesinger bases (BEMP and BTPP) (Scheme 2.16). Generally, the less-basic BEMP proved to be superior and tolerated several representative Michael acceptors [38],... 

Side Note 13.2. Neutral, but Superbaslc Schwesinger Bases ... 

Fig. 13.8. The strongest Schwesinger base metal-free, but as strong as alkali metal amides ...

Monoalkylation of an amino acid on a polymeric support using Schwesinger base (Table 8, entries 18, 19) [472, 473] (This reaction is also suitable for alkylating amino acids bearing an a-alkyl substituent so as to give a dialkylated product. Here, the amino function has to be protected as an aldimine.)... 

In some cases, when Schwesinger base is used in reaction sequences, removal of polymer-associated base may be difficult In such cases, a fivefold wash with CH2CI2/ACOH (4 1, v/v) may be employed. The loss of polymer-bound substrate attached to a Rink linker via amide or amine functions is very minimal during this treatment. 

The power of column-like reactors for continuous flow processes lies in the possibility to sequentially link them up in order to carry out multistep syntheses in solution in one run (see also Schemes 1 and 2). Lectka and coworkers utilized conventional fritted and jacketed columns for this purpose. These columns were filled with conventional functionalized polymeric beads [47]. The continuous flow was forced by gravity. En route to / -lactams polymer beads functionalized with the Schwesinger base 17, a cinchona alkaloid derivative 18 as a chiral catalyst, and a primary amine 19 were sequentially employed. They first guaranteed the generation of phenyl ketene from phenyl... 

Preparation of Phosphines from Metallated Phosphines. - Alkali metal-free phosphide anions have been shown to be formed under synthetically useful conditions in the equilibria between primary or secondary phosphines with the Schwesinger bases (23). Techniques have been developed for the preparation of alkali metal diphenylphosphide reagents in high purity, as evidenced by P nmr studies. The same paper reports a study of the course of the reactions between potassium diphenylphosphide and a series of aryl-, n-alkyl- and neopentyl-halides. The results provide the first evidence of the involvement of single electron transfer (SET) processes in the reactions of alkyl halides. This pathway is dominant in the case of neopentyl-type iodides, but plays only a minor role in the related reactions of neopentyl-type bromides and chlorides. No evidence was adduced of the involvement of SET processes in the reactions of unhindered... 

A similar strategy has also been used for t-Bu-P4 (Schwesinger base) ... 

Scheme 2.18 Domino Michael-iV-acyliminium cyclisation reaction catalysed by a combination of a chiral phosphoric acid and a polymer supported Schwesinger base.

In 2012, Pietruszka et al. reported a remarkable DKR of allg l 2,3-dihy-drobenzo[b]furan-3-carbo ylates achieved by using a combination of lipase Novozym 435 with the Schwesinger base, tert-butylimino-2-diethylamino-l,3-dimethylperhydro-l,2,3-diazaphosphorine (BEMP), immobilised on polystyrene to induce racemisation of the ester. The application of a basic... 

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