Mg-promoted double silylation of trifluoroacetimidoyl chlorides. A new entry to the fluorinated dianion equivalents

[reaction: see text] A Mg(0)/Me(3)SiCl system was found to be effective for the preparation of a novel fluorinated dianion equivalent. A one-pot reaction sequence involving reductive C-F and C-Cl bond cleavage reactions of trifluoroacetimidoyl chlorides afforded bis-silylated difluoroenamines. Subsequent carbon-carbon bond-forming reactions of the bis(silyl)enamines with two kinds of electrophiles gave a variety of difluorinated imines.     

A comparative study of the reactions of fluorinated oxi- and thiiranes with acyl chlorides

The CoCl₂-catalyzed reactions of fluorinated 1,2-oxi- and thiiranes with acyl chlorides were studied. It was found that a regioselective heterocycle opening reaction resulted in two isomers having normal and abnormal structure in a ratio predetermined by the substituents in both the starting heterocycles and acyl chlorides.     

Adamantyl-containing fluorinated 1,3-diketones

A convenient one-step procedure has been developed for the synthesis of fluorine-containing 2-(adamant-l-yl)-1,3-diketones by reaction of fluorinated 1,3-diketones with 1,3-dehydroadamantane. The products can be used as starting compounds for the preparation of new fluorinated adamantyl-containing heterocyclic compounds.     

Chemical Transformations of Tetracyclo[3.3.1.1<Superscript>3,7</Superscript>.0<Superscript>1,3</Superscript>]decane (1,3-Dehydroadamantane): VI. Reactions of 1,3-Dehydroadamantane with Carboxylic Acid Chlorides

1,3-Dehydroadamantane reacted with saturated carboxylic acid chlorides to give the corresponding 1-acyl-3-chloroadmantanes as the major products. In some cases, minor products of insertion into the C^α–H bond of acyl chloride were formed. The reactions of 1,3-dehydroadamantane with aromatic (heteroaromatic) carboxylic acid chlorides selectively afforded aryl (hetaryl) 3-chloroadamantan-1-yl ketones. The described reactions provide a synthetic route to difficultly accessible alkyl (aryl) ketones containing a 3-chloroadamantan- 1-yl group in one step under mild conditions with high yields.     

Fluorinated 2-benzoylcyclohexane-1,3-diones and their vinylogous acyl chlorides in the reactions with primary and secondary amines

The reaction of 5,5-dimethyl-2-[(3-fluoro- and 4-fluoro)benzoyl]cyclohexane-1,3-diones with primary and secondary amines affords their exocyclic enamine derivatives. Under similar conditions 5,5-dimethyl-2-(2-fluorobenzoyl)]cyclohexane-1,3-dione undergoes dehydrofluorination and intramolecular cyclization to give 3,3-dimethyl-2,3,4,9-tetrahydro-1H-xanthene-1,9-dione. The reaction of vinylogous substitution of the enol derivatives of the fluorinated 5,5-dimethyl-2-benzoylcyclohexane-1,3-diones (vinylogous acyl chlorides) with amines results in the formation of the endocyclic enaminoderivatives.     

Palladium catalyzed amination of vinyl chlorides: a new entry to imines, enamines and 2-amino-1,3-butadienes

Vinyl chlorides are employed for the first time in palladium catalyzed cross-coupling reactions with amines to furnish imines and enamines. The new methodology has been applied to the synthesis of 2-amino-1,3-butadienes, that could not be achieved from the corresponding bromides.     

Observation of 1,3-diketones formation in the reaction of bulky acyl chlorides with methyllithium

The formation of 1,3-diketones was observed in the reactions of bulky acyl chlorides with methyllithium. The reaction products depend on the steric hindrance around the carbonyl group of the acyl chloride and the electronic effect of the group(s) linked to the carbonyl. When the steric hindrance around the carbonyl group of the acyl chloride is big enough, the 1,3-diketone is the only product. In the case of the moderate hindrance around the carbonyl group of the acyl chloride, a moderate yield of 1,3-diketone is obtained and some tertiary alcohol is generated. When there is no steric hindrance around the carbonyl group of the acyl chloride, the tertiary alcohol is the only product. When the steric hindrance around the carbonyl group is moderate and an electron-donating group is connected to the carbonyl of the acyl chloride, all three products--ketone, 1,3-diketone and tertiary alcohol--can be isolated from the reaction mixture after long reaction times.     

Substrate-controlled selective proximal and distal C-C bond cleavage via lewis acid mediated O-acylation of 2-(arylmethylene)cyclopropylaldehyde: a stereoselective synthesis of bifunctional methylenecyclobutanes and 1,3-conjugated dienes

ZnCl2-mediated reactions of (E)-2-(arylmethylene)cyclopropylaldehyde 1 with various acyl chlorides provide a novel method for stereoselective synthesis of bifunctional methlylenecyclobutanes via a proximal-bond cleavage process. Nevertheless, when (Z)-1 was employed, the reactions give 1,3-conjugated dienes through distal-bond cleavage.     

Evaluation of Zard trifluoromethylketone synthesis for the preparation of potential bifunctional fluorinated synthons

In the quest for potential bifunctional fluorinated synthons, we examined the behavior of chlorodifluoroacetic and hexafluoroglutaric anhydride in their reaction with acid chlorides in the presence of pyridine under the conditions of Zard trifluoromethylketone synthesis. Chlorodifluoroacetic anhydride led easily to the expected chlorodifluoromethyl ketones in the case of relatively non-encumbered primary acid chlorides. In the case of hexafluoroglutaric anhydride we observed the unexpected formation of α substituted hexafluorocyclohexane-1,3-dione derivatives among with the corresponding fluorinated 3-chloro-cyclohexenones.     

The syntheses of fluorinated alkanesulfonamides and poly-(fluorinated alkanesulfonamides)

In order to synthesize poly-(fluorinated alkanesulfonamides) a series of model experiments were carried out: (1) reactions of fluorinated alkanesulfonyl fluorides with amines, (2) reactions of fluorinated alkanesulfonyl chloride with amines and (3) reactions of sodium salts of fluorinated alkanesulfonamides with alkyl iodides of fluorinated alkanesulfonic acid esters. Seventeen new fluorinated alkanesulfonamides were prepared in good yields, namely: R_FO(CF₂)₂SO₂NR¹R² (1a-h), R¹R²NSO₂R_FSO₂NR¹R² (2a-h) and [Cl (CF₂)₄O(CF₂)₂SO₂NH(CH₂)₃]₂ (3). Reaction of R_FSO₂NH₂ with equivalent amount of NaOCH₃ and methyl iodide was shown to give both the N-mono- and N,N-di-substituted amides. Consequently the N-monosubstituted alkanesulfonamides were chosen as monomers for syntheses of the poly-(fluorinated alkanesulfonamides) and two new polymers were synthesized. The effect of the condition of the polycondensation on M?_n of the polymers were discussed and elemental composition, ¹⁹F NMR, IR, M?_n, Tg, tensile strength, thermal and chemical stabilities of the polymers were measured. Several new perfluoroalkanesulfonyl chlorides CISO₂R_FSO₂Cl (4a-c) and fluorinated alkanesulfonic acid esters (6a-d) were synthesized. However, reaction of CFCl₂CF₂O(CF₂)₂SO₂F with AlCl₃ was found to give Cl₃CCF₂O(CF₂)₂SO₂F (5) instead of the expected sulfonyl chloride.     

Stereoselective synthesis of fluorinated 1,3-cis-diaminocyclopentanes

Several fluorinated 1,3-diaminocyclopentanes, previously reported to be useful RNA structural probes, can be prepared in a diastereoselective manner from a single bicyclic hydrazine precursor, in 3 to 9 steps.     

Halogenation of fluorinated cyclic 1,3-dicarbonyl compounds: new aspects of synthetic application

In order to elaborate on an approach towards 2-(fluoroacyl)phenols being the superior alternative to the conventional Fries-rearrangement based methodology, the behaviour of cyclic fluorinated 1,3-dicarbonyls in reactions with halogenating agents was examined. The synthetic relevance of the polyhalogenated compounds obtained was demonstrated by the synthesis of several new heterocycles. An aromatization via a halogenation-dehydrohalogenation sequence proved to be a rewarding synthetic route to 2-(fluoroacyl)phenols and previously unknown 3-(fluoroacyl)thiochromones. The structure of one of the synthesized compounds was confirmed by X-ray diffraction analysis.     

New fluorinated 1,3-vinylogous amidines as versatile intermediates: synthesis of fluorinated pyrimidin-2(1H)-ones

The condensation of the azaenolates derived from readily available ketimines with fluorinated nitriles offers an efficient and straightforward entry to new fluorinated 1,3-vinylogous amidines. These versatile compounds, in turn, react with triphosgene to yield new fluorinated pyrimidin-2(1H)-ones in high yields.     

A novel one-pot, two-step synthesis of N-acyl-1,3-thiazolidines and N-acyl-1,3-oxazolidines as potential double prodrugs of formaldehyde

A convenient and general one-pot, two-step protocol to prepare both N-acyl-1,3-thiazolidines and N-acyl-1,3-oxazolidines from formaldehyde, fatty acyl chlorides, and natural α-amino acids has been performed for the peculiar case of formaldehyde. In the presence of triethylamine to promote both the ring-forming process and the amide bond formation, subsequent addition of the acyl donor proved to be efficient to trap the preformed stable formaldehyde-derived 1,3-thiazolidine or the transient 1,3-oxazolidine using an appropriate ratio of formaldehyde.     

Partially fluorinated naphthalene derivatives from 1,4-dilithio-1,3-dienes and C6F6

Multi-substituted partially fluorinated aromatic compounds, such as naphthalene derivatives could be readily prepared by the reaction of 1,4-dilithio-1,3-dienes with hexafluorobenzene via double nucleophilic substitution. When these dilithium reagents were treated with hexachlorobenzene, chloropentafluorobenzene or bromopentafluorobenzene, chlorine-lithium or bromine-lithium exchange reactions, instead of nucleophilic substitution, took place.     

Fluorine-containing heterocycles: XVIII. Monofluoro derivatives of quinazolines and 1,3-benzothiazin-4-ones

5- and 7-Fluoro-substituted quinazolines and 1,3-benzothiazin-4-ones were synthesized starting from 2-amino-6-fluorobenzonitrile and mono- and difluoro-substituted benzoic acid derivatives. The reactivities of di- and tetrafluoro-substituted benzoyl chlorides and benzoyl isothiocyanates in cyclocondensations leading to fluorinated quinazolines and 1,3-benzothiazines were compared.     

几个烯胺的邻硝基苯甲酰化和在酸水解中发生的重排

为了了解芳酰基化的效率和双酰基衍生物的形成, 对几个典型醛和酮的吗啉烯胺进行了邻硝基苯甲酰化的探索。丁醛和异丁醛吗啉烯胺的酰化正常, 水解分别生成55%的2-(邻硝基苯甲酰基)丁醛(2)和40%的2-(邻硝基苯甲酰基)异丁醛(3)。3-戊酮和1, 3-二甲氧基丙酮的吗啉烯胺在酰化和水解时分别生成37%和14.8%相应的β-二酮的烯醇邻硝基苯甲酸酯(4)和(5)。4和5的酸水解发生意外的1, 5-和1,3-酰基转位, 分别生成3, 5-二甲基-2, 6-双(邻硝基苯基)吡喃-4-酮(6)和2-甲氧基-2-甲氧乙酰基-1, 3-双(邻硝基苯基)-1, 3-丙二酮(7)。环戊酮和环已酮吗啉烯胺的酰化分别产生9%和34%的双酰基烯胺(9a)和(9b),逐次酸水解得到2-(邻硝基苯甲酰基)环戊酮(11a)和-环已酮(11b)。在总酰化产物的直接水解中, 11a的产率可以达到81%, 而11b只有35%。对双酰化进行了一些讨论。     

Fluorocontaining 1,3-Dicarbonyl Compounds in the Synthesis of Pyrimidine Derivatives

Hexafluoroacetylacetone reacts with urea (thiourea) to yield respectively 4,6-bis(hydroxy)-4,6-bis(trifluoromethyl)hexahydropyrimidin-2-one(thione). The dehydration of the products and also reaction of nonsymmetrical fluoroalkyl-containing 1,3-diketones with urea (thiourea) afford substituted pyrimidines. The condensation of fluorinated 3-oxoesters and 1,3-diketones with benzaldehyde and urea (thiourea) results in 5-alkoxycarbonyl(acyl)-4-hydroxy-2-oxo(thioxo)-6-phenyl-4-fluoroalkylhexahydropyrimidines that on dehydration furnish 5-alkoxycarbonyl(acyl)-2-oxo(thioxo)-4-phenyl-6-fluoroalkyltetrahydropyrimidines. Ethyl 7-nonafluorobutyl-5-phenyl-2,3-dihydrothiazolo[3,2-a]pyrimidine-6-carboxylate hydrobromide forms in reaction of dibromoethane with ethyl ether of 2-thioxo-4-phenyl-6-nonafluorobutyltetrahydropyrimidine.     

Regioselectively nucleus and/or side-chain fluorinated 2-(Phenanthryl)propionic acids by an effective combination of radical and organometallic chemistry

Regioselectively nucleus and/or side-chain fluorinated 2-(phenanthr-1-yl)- and 2-(phenanthr-2-yl)propionic acids 1-5 were prepared using phenanthren-1(2H)-ones 6a-c as key intermediates. Thus, ethyl 2-(fluorophenanthryl)propionates 11 were obtained in good yields by Reformatsky reaction of 6a-c with ethyl 2-bromopropionate followed by dehydratation and DDQ-promoted aromatization of the resulting beta-hydroxyesters. Side-chain alkyl 2-hydroxy-2-(phenanthr-1-yl)propionates 14 were obtained by bromine/lithium permutation of dihydrophenanthryl bromides 12a-c with butyllithium followed by quenching of the lithiated intermediates with methyl pyruvate or ethyl 3,3,3-trifluoropyruvate and subsequent DDQ-promoted aromatization. The alkyl 2-hydroxy-2-(phenanthr-1-yl)propionates 25 were prepared by reacting 8-bromo-1,3-difluorophenanthrene 24 with butyllithium for 10 seconds at -110 degrees C and subsequent addition of the suitable pyruvate to the lithiated intermediates. Alkyl 2-hydroxy-2-(phenanthr-2-yl)propionates 26 and 29 were suitably obtained by site-selective metalation of 1,3-difluorophenanthrene 28 and the bromophenanthrene 24, respectively, with LDA followed by quenching of the metalated intermediates with the suitable alkyl pyruvate. Fluorination of the above alpha-hydroxypropionates with DAST, followed by the alkaline hydrolysis, allowed the expected 2-(phenanthryl)propionic acids 1-5 to be obtained in satisfactory overall yields.     

1,3-Diradical intermediates in 3H-pyrazole photolyses: 1,4 addition to dienes

The photolyses of pyrazolopyridazines (2a-c) lead to alkenes (4a-c). With added methanol, furan or buta-1,3-diene, intermediates (3a-c) are trapped as compounds (6a-c)–(8a-c) respectively.