Convenient Preparation of 1,3-Bis(dimethylamino)trimethinium Perchlorate, Tetrafluoroborate and Hexafluorophosphate

Arnold, Z.; Dvořák, Dalimil; Havránek, M.

doi:10.1135/cccc19961637

Cited by 9 publications

(9 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…24 Both the perchlorate and hexafluorophosphate salts of compound 23 were readily synthesized and isolated as light yellow crystals. 25 Screening the counterion, solvent, and concentration revealed that a 15 mM solution of hexafluorophosphate salt 23b in 70% aqueous ethylene glycol possessed a UV spectrum aligned with our needs (Figure 1). To filter light in our flow apparatus, the glycol solution of 23b was pumped through the inner lamp-jacket of the Hanovia apparatus (see the Supporting Information for details) from an external reservoir precooled to −78 °C.…”

Section: ■ Results and Discussionsupporting

confidence: 65%

See 1 more Smart Citation

Photorearrangement of [8]-2,6-Pyridinophane N-Oxide

et al. 2020

View full text Add to dashboard Cite

Reaction pathways operative when pyridinophane N-oxides are photoirradiated have been studied using time course analyses and careful isolation of photolabile intermediates with support from DFT calculations. Based on the data and the isolation of two previously unknown heterocyclophanes, we outline a unified mechanistic scheme that explains competing processes under varying photochemical conditions.

show abstract

Section: ■ Results and Discussionsupporting

confidence: 65%

“…Fortunately, published spectra of vinamidinium perchlorate ( 23a ) suggested it could serve as a solution filter with transmissive character in the region around 240 nm . Both the perchlorate and hexafluorophosphate salts of compound 23 were readily synthesized and isolated as light yellow crystals …”

Section: Resultsmentioning

confidence: 99%

Photorearrangement of [8]-2,6-Pyridinophane N-Oxide

et al. 2020

View full text Add to dashboard Cite

show abstract

“…It has also to be isolated by crystallization from a viscous solution in aque-ous DMF at -10 to -35°C. Other salts of related vinamidinium cations previously described and used by Arnold and others include tetrafluoroborates, [7][8][9] and hexafluorophosphates. 9…”

Section: Figurementioning

confidence: 99%

Valuable Synthetic Building Blocks: Useful 2-Substituted 5-Aminopyrimidines from a Stable Precursor

Dousson¹,

Heron²,

Hill³

2005

Synthesis

View full text Add to dashboard Cite

-S u b s t i t u t e d 5 -A m i n o p y r i m i d i n e s f r o m a S t a b l e P r e c u r s o rAbstract: An efficient large-scale synthesis of 5-aminopyrimidine derivatives is described. The dihexafluorophosphate salt of a vinamidinium cation important in 5-aminopyrimidine synthesis has been prepared as a stable, easily purified intermediate. It has been used to prepare several 2-functionalized aminopyrimidines, valuable as synthetic building blocks.2,5-Disubstituted pyrimidines with have been widely synthesized. However, very few methods are available for the preparation of otherwise unsubstituted 2-functionalized 5-aminopyrimidines 1 or related 2 compounds. Nevertheless, such compounds are valuable synthetic building blocks. Present syntheses are unsuitable for large-scale chemistry, as they use hazardous precursors such as potentially explosive nitromalonaldehyde 3 or vinamidinium salts. Key compounds derived from the latter include 2, accessed by Arnold et al. 4 via the vinamidinium diperchlorate 3a 5 ( Figure 1). Figure 1Recently, we required access to a wide variety of 2-functionalized 5-aminopyrimidines. Some of these were used in the preparation of potential anti-cancer compounds or their precursors, by reaction with 4-chloroquinazolines as described in our recent patent application 6 and as exemplified in the conversion of 4 to 5 (Scheme 1).The likely thermal-and proven shock-sensitivity of vinamidinium perchlorate salts 7 made the salt 3a unsuitable for use by us as a large scale intermediate. It has also to be isolated by crystallization from a viscous solution in aqueous DMF at -10 to -35°C. Other salts of related vinamidinium cations previously described and used by Arnold and others include tetrafluoroborates, 7-9 and hexafluorophosphates. 9 Scheme 1We were unable to isolate the ditetrafluoroborate salt 3b usefully owing to its high solubility, and therefore turned our attention to the dihexafluorophosphate. 10 Hexafluorophosphate salts of amines and similar compounds are more easily isolated and less water-soluble than most other salts, for instance as diazonium salts in the Balz-Schiemann reaction; 11 also, widely used reagents such as HATU are commonly supplied as stable non-hygroscopic hexafluorophosphate salts.We have prepared the vinamidinium species as its dihexafluorophosphate salt 3c and have shown it to be an easily isolated, stable salt. The vinamidinium species was prepared, using a modification of Arnold's conditions, 5 from glycine hydrochloride in DMF and phosphorus oxychloride (see safety note 12 ). Research into improved preparations of similar salts from other less volatile formamides is ongoing.In our hands Arnold's original reaction conditions of 125°C for two hours gave, in addition to the product 3c, significant amounts of a by-product (Scheme 2) that formed a hexafluorophosphate salt inseparable from 3c; data from NMR and mass spectroscopy suggested this impurity was the previously undescribed salt 6. This presumably forms by attack on the product by dimethylamine generated ...

show abstract

“…However, increasing the concentration of the nucleophile by the addition of 1 equiv of KI restored the yield to acceptable levels. The N , N -dimethyl analogue 3c has previously been prepared from propargyl alcohol or ethyl vinyl ether . The 1,4-diazepinium hexafluorophosphate salt 1e (entry 5) was also reduced under these conditions.…”

mentioning

confidence: 99%

“…The N,N-dimethyl analogue 3c has previously been prepared from propargyl alcohol or ethyl vinyl ether. 13 The 1,4-diazepinium hexafluorophosphate salt 1e (entry 5) was also reduced under these conditions.…”

mentioning

confidence: 99%