Thiophene-fused boracycles as photoactive analogues of diboraanthracenes

The construction of thiophene-fused analogues of diboraanthracenes with different aryl substituents through boron-mercury exchange followed by the nucleophilic replacement of the chlorines of dichlorodiboradithiophene 2 with Grignard reagents is reported....

Solid-Phase Insertion of N-mercaptoalkylglycine Residues into Peptides

N-mercaptoalkylglycine residues were inserted into peptides by reacting N-free amino groups of peptides, which were initially synthesized on 2-chlorotrityl resin (Cltr) using the Fmoc/tBu method, with bromoacetic acid and subsequent nucleophilic replacement of the bromide by reacting with S-4-methoxytrityl- (Mmt)/S-trityl- (Trt) protected aminothiols. The synthesized thiols containing peptide–peptoid hybrids were cleaved from the resin, either protected by treatment with dichloromethane (DCM)/trifluoroethanol (TFE)/acetic acid (AcOH) (7:2:1), or deprotected (fully or partially) by treatment with trifluoroacetic acid (TFA) solution using triethylsilane (TES) as a scavenger.

Substituted pyridopyrimidinones, Part IV: 2-chloro-4h-pyrido[1,2-a]pyrimidin-4-one as a synthone of some new heterotricycles

2-Chloro-4H-pyrido[1,2-a]pyrimidin-4-one (1) was utilized as a synthone precursor to prepare novel heterotricyclic systems. 2-Azido and 2-hydrazino derivatives (2 and 3) were obtained by nucleophilic replacement evolving compound 1. The hydrazine derivative 3 was transformed into the azido derivative 2 by nitrosation. Treatment of compound 3 with [bis(methylthio)methylene] malononitrile afforded 2-pyrazolylpyridopyrimidine 4. When compound 1 was reacted with 5-amino-3-(methylthio)-1H-pyrazole-4-carbonitrile, the same compound 4 was obtained with no evidence for the production of (pyrazolylamino) pyridopyrimidine 5 or pyrazolodipyridopyrimidine 6. Poly-functionalized dipyridopyrimidine 8 was obtained by reaction of compound 1 with 2-[(methylthio)-( phenylamino)methylene]propanedinitrile. Cyanoguanidine was reacted with compound 1 to afford N-pyridopyrimidinylguanidine 9, which was subjected to cyclization reaction, in presence of piperidinium acetate, to give pyridopyrimidopyrimidine 10.

Compounds R1R2EMMe3 (E = P, As; M = Si, Sn) - Convenient and Versatile Reagents for the Syntheses of Tertiary (Fluoroaryl)phosphanes and -arsanes

Synthetic and mechanistic aspects of nucleophilic replacement of fluorine in fluorobenzenes, fluoropyridines and fluoroquinolines by phosphanyl and arsanyl groups via their reactions with R1R2EMMe3 (E = P, As; M = Si, Sn; R1, R2 = Me, i-Pr, t-Bu, Ph, etc.) reagents are considered.

Preparation of Dialkylamino-Substituted Benzenes and Naphthalenes by Nucleophilic Replacement of Fluorine in the Corresponding Perfluoroaromatic Compounds

The reactions between hexafluorobenzene (HFB) and octafluoronaphthalene (OFN) with secondary aliphatic amines (pyrrolidine, dimethylamine and piperidine) and lithium amides (pyrrolidide, dimethylamide and piperidide) have been investigated both experimentally and (in part) theoretically. With amines HFB, depending on the selected conditions, gives either di-substituted products or a complex mixture of di-, tri- and tetrasubstituted compounds. Under similar conditions OFN produces almost exclusively the 2,3,6,7-tetrasubstituted compound. Interaction of HFB with the more nucleophilic lithium amides results in the replacement of four fluorines giving 1,2,4,5-tetrasubstituted difluorobenzenes, while OFN under similar conditions with lithium pyrrolidide produces an inseparable mixture of 1,2,4,5,6,8-hexa- and 1,2,3,4,5,6,8-hepta-substituted derivatives. With lithium dimethylamide, it is possible to substitute six (in dioxane) or seven (in THF) fluorines in OFN. Lithium piperidide in all employed solvents reacts with OFN to give only the 1,2,4,5,6,8-hexasubstituted derivative. Theoretical calculations indicate that with lithium dimethylamide the third fluorine is substituted at position 1, whereas with dimethylamine it is position 3. The basicities of selected hexaand heptakis(dialkylamino)naphthalenes have been measured; they are all stronger bases than 1,8- bis(dimethylamino)naphthalene, although by less than expected.