Tetramethylguanidinium

Cleavage of this group is achieved with tetramethylguanidinium syn-2-pyridinecarboxaldoxime. Tris(hexafluoro-2-propyl) phosphites are sufficiently reactive to undergo transesterification with alcohols in a stepwise fashion. ... 

Several 5,6-disubstituted-3-azido[l,2,4]triazine-l-oxides 1021 were prepared (77JHC1221) by treatment of 1020 with nitrous acid. 3-Azido[l, 2,4]-triazine-2-oxide 1023 was prepared by reacting the corresponding 3-bromo derivative 1022 with either tetramethylguanidinium azide in chloroform or sodium azide in aqueous acetone. These azido derivatives were proven to exist in the open-chain form by H- and l3C-NMR and 1R spectra (77JHC1221) (Scheme 191). 

Tetramethylguanidinium azide, an azide salt that is readily soluble in halogenated solvents, is a useful source of azide ions in the preparation of azides from reactive halides such as a-haloketones, a-haloamides, and glycosyl halides.74... 

Trisubstituted imidazoles have been synthesized from 1,2-diketones or a-hydroxyketones with ammonium acetate in very short reaction times with excellent yields in the presence of l,l,3,3-VAr V ,(V -tetramethylguanidinium trifluoroacetate as an ionic liquid <06SC65>. Iodine acted as an efficient catalyst in the synthesis of 1,2,4,5-tetraarylimidazoles 93 using benzoin 91,... 

N-Proteetkm of amino acids (3, 36). r-Bulyloxycarbonyl (BOC) amino acids (2) can be prepared in 80-l(K)% yield by the reaction of 1,1,3,3-tetramethylguanidinium salts of amino acids (I) with r-butyl azidoformatc in DMF. ... 

Optically active a-azido acids as versatile a-amino acid synthons are obtained by diaste-reoselective halogenation of chiral auxiliary-based enols or enolatest followed by stereospecific azide displacement by A(A(A, A -tetramethylguanidinium azide or alternatively... 

The reaction of acid chlorides with tetramethylguanidinium azide also proceeds under very mild con-ditions. Using this technique even r-alkyl azidoformates may be prepared (Scheme 38). Quantitative yields of acyl azides (in solution) are reported for the interaction of acid chlorides in toluene with HNs/pyridine at 0 °C. Even sterically hindered educts are smoothly converted into acyl azides. If tetraalicylammonium azides are used, the use of hazardous hydrazoic acid is avoided. ... 

The base hydrolysis under harsh conditions very often brings about undesired cleavage of phosphates. In contrast, removal of an o- orp-chlorophenyl protecting group by lV ,iV, iV, /V -tetramethylguanidinium ryn-p-nitrobenzaldoxymate (NBO) (108 equation 65) or syn-pyridin-2-aldoxymate (PAO) (109) is achievable at room temperature and no side reaction occurs. The 8-quinolyl phosphate (110 equation 66) is also hydrolyzed under mild conditions with the assistance of a stoichiometric amount of ZnCb or CuCb salt. ... 

In place of sodium azide, which has low solubility in common organic media, use of a mixture of hy-drazoic acid and pyridine, tetrabutylammonium azide or tetramethylguanidinium azide has been recommended. One of the most useful and safe alternatives is trimethylsilyl azide (50), which reacts with various acyl chlorides or anhydrides to give isocyanates directly, under thermal conditions (Scheme... 

Preparation. Sakai and Anselme1 recommend that the reagent be prepared by the reaction of /-butyl chloroformate and tetramethylguanidinium azide (2,403-404) ... 

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