REACTIONS WITH 3-CHLORO-1,2-BENZISOTHIAZOLIUM CHLORIDES: A NEW SYNTHESIS OF 3-AMINO-BENZO [B] THIOPHENES

Abstract

3-Chloro-1,2-benzisothiazolium chlorides 1 react with activated methylene groups of ketones. Via a ring-opened intermediate 2, 2,3-dihydro-3-imino-benzo [b] thiophenes 3 are obtained, which may be cleaved to the 3-amino-benzo [b] thiophenes 4 and 5.     

Synthesis of Organophosphorus Compounds with ‒P˭P≡ and ‒P˭S˭ Units

Abstract

The lithium phosphide tetrahydrofurane complexes 1 react with phosphinic acid chlorides (2) to yield diphosphenes (4), possessing a tri- and a quinquevalent phosphorus atom; the diphosphane oxides 3 are regarded to be intermediate steps of the transformation.     

Unexpected Formation of Cyclic Hydroxamic Acids from O-(2-Aminobenzoyl) Hydroxylamine

Cyclic hydroxamic acids 3 and 4 are the unexpected products in the reaction of 0-(2-aminobenzoyl) hydroxylamine 1 and orthoesters, acid chlorides, ethyl chloroformate.     

1,2- and 1,3-diphosphetanes from alkylidenephosphines

Abstract

Alkyl- or arylbis(trimethylsilyl)phosphines as well as tris(trimethylsilyl)phosphine and the corresponding arsines react with acyl chlorides to give [1-(trimethylsiloxy)alkylidene]phosphines 1 and -arsines 2; most of their 2,2-dimethylpropylidene derivatives are thermally stable at room temperature. With the same class of phosphines as starting compounds and carbon disulfide [bis(trimethylsilylsulfano)methylidene]phosphines 3 are formed, whereas [(dialkylamino)methylidene]-4 and [diarylmethylidene]phosphines 5 or the corresponding arsines 6 and 7 can be obtained from acyl amides or ketones.¹     

A Simple and Efficient New Glycal Synthesis

Abstract

Potassium-graphite laminate (C₈K) in oxolane almost instantaneously converts O-alkyl and O-aUcylidene pyranosyl and furanosyl chlorides under extremely mild conditions and in high yields into pyranoid and furanoid glycals, which in the presence of an additional mole of C₈K, are efficiently O-alkylated or O-silylated In easily conducted one-pot reactions.     

CHLOROSULFONATION OF N-PHENYLMORPHOLINE,BENZOTHIAZOLE, 2-METHYL BENZOTHIAZOLE AND TRIPHENYLOXAZOLE

Abstract

N-Phenylmorpholine (1) reacted with chlorosulfonic acid to give the p-sulfonyl chloride (2), which was characterized as the sulfonamides (3–5). Benzothiazole (6) was converted into the sulfonyl chloride (7) by sequential treatment with hot chlorosulfonic acid and thionyl chloride. Reaction of (7) with amines afforded the derivatives (8–10); NMR spectral analysis of the dimethylamide (8) indicated that it was a mixture of the 4- and 7-isomers. Chlorosulfonation of 2-methylbenzothiazole (11) was achieved by heating with chlorosulfonic acid with or without thionyl chloride. The chloride (12) was converted into amides (13–19). Study of the NMR spectra indicated that mixtures of the 5- and 6-isomers were formed. 2,4,5-Triphenyloxazole (20) reacted with chlorosulfonic acid to give either the mono-(21), bis (23) or bis-tris sulfonylchlorides (23, 34); these were converted into 14 sulfonamides. 2-(p-Nitrophenyl)-4,5-diphenyloxazole (41) reacted with hot chlorosulfonic acid to give the bis-sulfonyl chloride (42), characterized as the dimethylsulfonamide (43). Attempts to form the pure monosulfonyl chloride and to mono nitrate 2,4,5-triphenyloxazole (20) were unsuccessful.     

REACTIONS OF DITHIOLETHIONES WITH N,N-DICHLOROAMIDES

Abstract

Dependent on the starting materials and the reaction conditions N,N-dichloroamides Cl₂N-X (X = COaryl, CO₂alkyl, SO₂aryl, SO₂N(alkyl)₂) react with dithiolethiones 1 and 5 to N-(dithiolyliden)amides 2, 6, S-(dithiolylidene)sulfimides 3, thionoxides 7 and dithiolones 4, 8. The mechanisms have been studied.     

Reaction Pathways upon Interaction of Allenic Phosphonates with Selenyl Chlorides

Abstract

Studies were performed on the reaction between alkyl- and arylselenyl chlorides with esters of allenic phosphonic acids, variously substituted at their terminal C-atom. With the esters of the C-3 diasubstituted acids the reaction is highly regioselective and only oxaphosphol heterocyclization occurs to 2,5-dihydro-1,2-oxaphosphols 21-e. With the esters of the propadiene phosphonic acid the reaction is regio- and (Z)-stereoselective: only the 2,3-adducts 3a-b are formed, where the (Z)-isomer and the allenic phosphonates 4a-b are prevalent, as a result of 1,3-sigmatropic isomerization of 3a-b. With the esters of the C-3 monosubstituted acids, complex reaction mixtures are formed. From them were isolated: (E)- and (Z)-isomers of 2,5-dihydro-1,2-oxaphosphols 2f-j; (E)-and (Z)-isomers of the 2,3-adducts 3c-h; (E)-and (Z)-isomers of 4c-f; and (E)-and (Z)-isomers of the 1,2-adducts 5a-d. The reaction partially loses its regioselectivity, but the (Z)-stereoselectivity is preserved:     

SYNTHÉSE DE THIOÉTHERS D'ACIDES PROPYLBORONIQUES S - BENZYLÉS

The protection of the hydroxy group of p-cresol 1 by o-silylation gives derivatives 2 and 3 , the methyl group of which can be brominated by NBS. The phase transfer catalysis applied to 4 and 5 is a good way which permits the mild introduction of the allylthio group ( 6 and 7 ). Hydroboration applied to silylated compounds 8 and 9 , followed by methanolysis and hydrolysis leads to target acids 10 and 11 in a good yield.

La protection du groupement hydroxy du p-crésol 1 par o-silylation donne les dérivés 2 et 3 ce qui permet de bromer le substituant méthyle par le N-bromosuccinimide (NBS). La catalyse par transfert de phase (CTP) appliquée aux produits 4 et 5 est une bonne méthode pour introduire un groupement allylthio (composés 6 , 7 ). L'hydroboration des composés silylés 8 et 9 , suivie d'une méthanolyse et d'une hydrolyse permet d'accéder aux acides cibles 10 et 11 avec de bons rendements.     

Syntheses of α-Amino Phosphinic Acids via Oxo-iminium Salts

Nitrones 2a , 2b obtained from the aldehydes 1a , 1b , are used for the syntheses of the N-ethoxy iminium salts 4a and 4b . In the following procedure 4a and 4b react to several esters of phosphinic acids 6a - 6d .     

Synthesis of the Oligosaccharide Moieties of Musettamycin,Marcellomycin and Aclacinomycin A,Antitumor Antibiotics

Abstract

Condensation of benzyl 2,3,6-trideoxy-3-trifluoroacetamido-α-L-lyxo-hexopyranoside (5) with 4-O-acetyl-3-O-benzyl-2,6-dideoxy-α-L-lyxo-hexopyranosyl bromide (10) carried out under Koenigs-Knorr conditions gave 12. Total deprotection of 12 and N-dimethylation at C-3 led to 17 while selective removal of the 4-O-acetyl group led to 13, a synthetic intermediate for preparing 24 and 33. Condensation of 13 with di-O-acetyl-L-fucal (18) or 4-O-acetyl-L-amicetal (25) in the presence of N-iodosuccinimide followed by hydrogenolysis of the C-2-I bond gave 20 and 27 respectively. The trisaccharide 24 then was obtained from 20 by the same sequence of reactions used to convert 12 into 17. After deacetylation and oxidation, this set of reactions also transformed 27 into 33.     

Accessibility of D-Mannopyranoside Glycosylating Synthons by Acetolysis for Preparations of Oligosaccharide Moieties of N-Linked Glycoproteins

Abstract

Selective acetolysis of methyl 2, 3, 4, 6-tetra-O-benzyl-α-D-manno-pyranoside (2) allows for easy preparation of 1-acetates of 2, 3,4, 6-tetra-O-benzyl (5), 6-O-acetyl-2, 3, 4, tri-O-benzyl-(6), 4, 6-di-O-acetyl-2,3-di-O-benzyl-(7), 3, 4, 6-tri-O-acetyl-2-O-benzyl-(8), and 2, 4, 6-tri-O-acetyl-3-O-benzyl-D-mannopyranoside (9). 8 and 9 formed are separated by preparative HPLC in 30-60g scale. The time course of previously described acetolyses of 3, 4, 6-tri-O-benzyl- 1, 2-O-(1-methoxyethyidene)-β-D-mannopyranose (3), and methyl 2, 3-dt-O-benzyl-4, 6-O-benzylldene-α-D-mannopyranoside (4) giving 9, 1, 2, 6-tri-O-acetyl-3, 4-di-O-benzyl-(10), and 1, 2-di-O-acetyl-3, 4, 6-tri-O-benzyl-(11) α-D-mannopyranose as well 7 have been studied.     

A THEORETICAL TREATMENT OF THE SULFUR-CONTAINING ANALOGS OF CYCLOBUTADIENE,CYCLOOCTATETRAENE, BUTALENE,AND OCTALENE

Abstract

Several coordination complexes of cyclobutadiene (I) have been prepared (e.g., cyclobutadiene iron tricarbonyl [1]) and cyclooctatetraene (II) is a well-known compound (for a potentially planar form of cyclooctatetraene, see [2]). Although butalene [3] (III) has not been synthesized so far, octalene (IV) has been obtained by Vogel and co-workers [4,5]. Recently we have carried out a theoretical study of the physical and chemical properties of butalene (III) and octalene (IV), and of the various annelated butalenes and octalenes [6,7] using the HMO and SCF-MO (PPP) quantum-chemical methods as well as the structure-resonance theory and graph theoretical methods. Numerous theoretical data are available in the literature on cyclobutadiene (I) and cyclooctatetraene (II).     

Synthesis of C-Glycosyl α-Glycines

Abstract

A scheme of asymmetric synthesis of C-glycosyl α-glycines is described. Reductive hydrolysis of 2-deoxy-3,5-di-O-p-toluoyl-β D-erythropentofuranose 1-cyanide (4) in the presence of N,N-diphenylethylenediamine gave the imidazolidine 5, which was converted to 2,5-anhydro-3-deoxy-4,6-di-O-p-toluoyl-β-D-allose (3)by acid hydrolysis. The aldehyde (3), chiralamine, benzoic acid and t-butyl isocyanide four component condensation afforded in good yield two diastereomeric adducts (6a and 6b), which were separated by column chromatography and deblocked to furnish 2-deoxy-β-D-erythropentofuranosyl R and S-glycines (1a) and (1b).     

An Improved Synthesis of 2′-Hydroxy-3′,4′,6′-trimethoxyacylophenones

A wide variety of 2′-hydroxypolymethoxyacetophenones and propiophenones, e.g. 1a and 1b are used in the synthesis of flavone and ehromone natural products.¹ Repeated attempts to prepare 1a and 1b by reacting 1,2,3,5-tetramethoxybenzene 2 with acetyl or propionyl chlorides and AlCl₃ in ether² gave products which were difficult to purify.³ We traced the problem to ring-ethoxy contaminants which were isolated and tentatively identified as 3a and 3b.     

1,1-DIANIONS OF ALKYL PHENYL SULPHONES AS SYNTHETIC INTERMEDIATES IN CYCLIZATION REACTIONS

Abstract

α-Sulphonyl carbanions are known to be good nucleophiles both in intermolecular and in intramolecular reactions¹. In the same way gem-dimetalloderivatives of alkyl phenyl sulphones I a,b readily add to aldehydes and ketones to give the (β-hydroxy compounds II in the case of dilithioderivatives Ia, while from dimagnesioderivatives Ib α, β-unsaturated sulphones III are also obtained².     

Synthesis and Structure Elucidation of 8-Methyl- and 9-Methyl-exo-2-carbomethoxy-endo-tricyclo[5.2.1.02,6]deca-3,8-dien-5-ones

A mixture of 1-methyl- and 2-methyl-1,4,4a,8a,-tetrahydro-endo-1,4-methano-naphthalene-5,8-diones ( 2 & 3 ) was chemically transformed into separable methyl substituted tricyclo[5.2.1.0^2,6]decadienones 7 , 8 & 9 . The structure of 8 & 9 were elucidated via Cope rearrangement of their corresponding allylic alcohols ( 10 & 11 ) to furnish 12 & 13 respectively.     

Six-Membered Nitrogen Heterocycles from Xylaramide and Ribaramide

Abstract

N,N'-Diacetyl-tri-O-acetylxylaramide (8) and N,N'-diacetyl-tri-O-acetylribaramide (20) were directly converted to the nitrogen heterocycle 6-acetamido-2,6-diacetyloxy-aza-1,4-cyclohexadlen-3-one (9) with sodium acetate in acetic anhydride. Treatment of tri-O-acetylxylaramide (7) or tri-O-acetylribaramide (19) with the same solvent-base combination gave the highly crystalline 2,3,5,6-tetraacetyloxypyridlne (30) as the principal product. Mechanistic considerations for the formation of these nitrogen heterocycles are presented.     

Phospha-alkynes - Useful Building Blocks in Organic Chemistry1

Abstract

The syntheses of phospholes (7, [3+2]-cycloaddition), bicyclophosphaalkenes (17, [4+2]-cycloaddition), and phosphabenzenes (15, [4+2]-cycloaddition followed by an extrusion process) starting from the phosphaalkynes (4) are described. The 2–Dewar phosphabenzene 18, obtained from the cyclobutadiene 21 and 4 (R =^tBu), is the starting material for the synthesis of the valency isomers 19, 20, 22, and 23.     

Synthesis and Reactivity of Benzyl 2-O-Trifluoromethyl-Sulfonyl- and Benzyl 3-O-Trifluoromethylsulfonyl-β-D-Ribofuranoside - The first Evidence of Trifluoromethyl-Sulfonyl (Triflyl) Migration in Carbohydrates

Abstract

Benzyl 2,5-di-O-(tert-bstvldimethvl)silvl-3-O-triflvl-β-D-ribofsranoside (13) underwent triflyl migration upon O-desilylation with triethylammonium hydrogen fluoride in tetrahydrofuran affording benzyl 2-O-triflyl-β-D-ribo-furanoside (7) in ca. 5% yield, together with three other products, benzyl 3-O-triflyl-β-D-ribofuranoside (17), benzyl 2-O-(tert-butyldimethyl)silvl-3-O-triflyl-β-D-ribo-furanoside (18) and benzyl 3-deoxy-β-D-glvceropento-furanos-2-uloside (16). In order to confirm the triflyl migration, a series of reactions were performed.