Synthesis and Stereochemistry of Novel Dibrominated 1,5-Dioxaspiro[5.5]undecane Derivatives

 The synthesis and stereochemistry of new dibrominated spiro-1,3-dioxane derivatives are reported. Investigations by means of NMR methods and single crystal X-ray diffraction for two compounds revealed the high regio- and diastereoselectivity of the bromination reaction of some new spiro-1,3-dioxanes and the asymmetric induction of the chiral carbon atom located in the spiro skeleton.     

Synthesis and Stereochemistry of Some New Spiro-1,3-perhydrooxazines

Summary.  The synthesis and the stereochemistry of new spiro-1,3-perhydrooxazines are reported. The stereoisomerism of these compounds is discussed considering the data of conformational analysis, the helical chirality of the spiro[5.5]undecane skeleton, and the triligand virtual chiral center belonging to the 1,3-perhydrooxazine ring. Received February 21, 2000. Accepted (revised) April 18, 2000     

Asymmetric synthesis of 1,3-thiazolidine-derived spiro-β-lactams via a Staudinger reaction between chiral ketenes and imines

Enantiomerically pure 1,3-thiazolidine-derived spiro-β-lactams were stereoselectively synthesised by means of a Staudinger ketene–imine reaction starting from optically active N-Boc-1,3-thiazolidine-2-carboxylic acid derivatives and imines. The reactions were stereoselective and afforded spiro-β-lactams with a relative trans-configuration. The absolute configuration of the new stereocentres was assigned on the basis of the well-accepted mechanism and confirmed by means of the X-ray crystal structure analysis. The spiro-β-lactams were transformed into enantiomerically pure chiral monocyclic β-lactams by opening the thiazolidine ring and recovering the chiral auxiliary.     

Synthesis and Stereochemistry of Some New Spiro-1,3-perhydrooxazines

 The synthesis and the stereochemistry of new spiro-1,3-perhydrooxazines are reported. The stereoisomerism of these compounds is discussed considering the data of conformational analysis, the helical chirality of the spiro[5.5]undecane skeleton, and the triligand virtual chiral center belonging to the 1,3-perhydrooxazine ring.     

Chiral spiro-β-lactams from 6-diazopenicillanates

Chiral spiro-β-lactam derivatives have been prepared via stereoselective 1,3-dipolar cycloaddition of 6-diazopenicillanates. Using dipolarophiles such as acrylonitrile, acrylates or methyl vinyl ketone spiro-2-pyrazoline-β-lactams were obtained, whereas the cycloaddition with N-substituted-maleimides afforded spiro-1-pyrazoline-β-lactams. 6-Diazopenicillanates also reacted with electron-deficient alkynes to give the corresponding spiro-3H-pyrazole-β-lactam as single product. The observed stereoselectivity can be explained considering that the major product results from the addition to the less sterically hindered α-side of the β-lactam. Microwave-induced denitrogenation of spiro-1-pyrazoline-β-lactams allowed the stereoselective synthesis of novel spirocyclopropyl-β-lactams. The rationalization of the observed selectivity was supported by electronic structure calculations.     

Synthesis of new polyhedral oligomeric silsesquioxane derivatives as some possible antimicrobial agents

1,3-Dipolar cycloaddition reactions were studied to synthesize Polyhedral oligomeric silsesquioxane (POSS)-based norbornyl imide derivatives containing izoxazoline groups in good yields. And also 1,3-dipolar cycloaddition reactions of azomethine ylides with POSS-based norbornene dipolarophiles for a synthesis of the novel POSS-based norbornane-fused spiro-1,3-indandionolylpyrrolidines are reported. All newly synthesized POSS compounds were structurally characterized by FTIR, ¹H, ¹³C NMR, HRMS and GC/MS analyses.     

ORGANOPHOSPHORUS COMPOUNDS,XXX

Abstract

Fluoroenylidenetriphenylphosphorane (1a) reacts with maleic and phthalic anhydrides to give lactones 2a and 3, respectively. The same reagent (1a) extrudes sulphur from thiophthalic anhydride yielding the spiro-1,3-indandione derivative 4. The infrared and mass spectra of the new products are discussed.     

One-pot electrosynthesis of 2,3-bis(spiro-2-indanyl-1,3-dione)-indeno[1,2-b]furan-4-one

The 2,3-bis(spiro-2-indanyl-1,3-dione)-indeno[1,2-b]furan-4-one has been synthesized by cathodic reduction of 2,2-dibromo-1,3-indandione in dichloromethane-Bu₄NBF₄. In contrast, tris-indanedione was the main product when acetonitrile was used as a solvent. Sunlight exposition of the dispiro compound afforded the tris-indandione in quantitative yield.     

Asymmetric synthesis of multicyclic spiro-1,3-indandiones via a cascade Michael/Michael reaction of curcumins and 2-arylidene-1,3-indandiones

An organocatalytic cascade Michael/Michael reaction between curcumins and 2-arylidene-1,3-indandiones has been studied. Prolinol, chiral thiourea-tertiary amines, and cinchona alkaloids were evaluated as catalysts. Quinine was identified as the best catalyst for the transformation. Multicyclic spiro-1,3-indandiones were prepared in moderate to excellent yields, diastereoselectivities, and enantioselectivities.     

Highly diastereoselective synthesis of dispiro[1,4-dithiane/dithiepane]bisoxindoles via Stevens rearrangement

Synthesis of dispiro[1,4-dithianes/dithiepanes]bisoxindoles from the reaction of 3-diazo-2-oxindoles and spiro-1,3-dithiolaneoxindole or -1,3-dithianeoxindole derivatives in the presence of rhodium(II) acetate dimer as a catalyst was demonstrated under mild conditions in a highly diastereoselective manner. These dispiro-compounds were obtained via intermolecular sulfonium ylides and followed by Stevens rearrangement.     

Synthesis of chiral spiropyrazoline-β-lactams and spirocyclopropyl-β-lactams from 6-alkylidenepenicillanates

Chiral spiropyrazolinepenicillanates were obtained in a stereoselective fashion via 1,3-dipolar cycloaddition reactions of 6-alkylidenepenicillanates with diphenyldiazomethane, phenyldiazomethane, and diazomethane. Microwave-induced ring contraction of spiro-1-pyrazoline-β-lactams leading to chiral spirocyclopropylpenicillanates is also described.     

Synthesis of annulated oxa-triquinanes and oxa-diquinanes via cascade Michael addition-intramolecular alkylation involving α-halodicyclopentadienones

Base Mediated Michael addition of 1,3-dicarbonyl compounds to α-halodicyclopentadienones followed by cyclization of the intermediate Michael adducts leads to novel annulated dihydrofurans as single diastereomers. Such fused dihydrofurans, which are also oxa-triquinanes and oxa-diquinanes, undergo retro-Diels-Alder reaction to give cyclopentadiene-eliminated products in excellent yield. Certain 1,3-dicarbonyl compounds exhibited a different reactivity profile with α-halodicyclopentadienones leading to spiro-cyclopropanes fused to dicyclopentadiene skeleton.     

SYNTHESIS OF SPIRO [1,3-BENZODIOXOLE-2,4′-(3′H) QUINAZOLINES]

Abstract

In the present investigation, the authors could obtain a new series of spiranes (1) through the reaction of the high potential quinone tetrachloro-o-benzoquinone with 2-aryl-3-phenyl-3H-quinazoline-4-thiones. Thus, 2,3-diphenyl- (2a), 2-p-tolyl-3-phenyl- (2b) and 2-p-anisyl-3-phenyl- (2c)-3H-quinazoline-4-thiones react readily with tetrachloro-o-benzoquinone, in boiling toluene, to give the corresponding spiro-1,3-benzodioxole-2,4′-(3′H)-quinazolines (1a-c), respectively.     

A facile microwave assisted synthesis of spiro-1,3-oxazines from N-(2-(cyclohex-1-en-1-yl)ethyl)amides

A mild and efficient methodology has been developed for the synthesis of spiro-1,3-oxazine derivatives by the microwave assisted cyclization of N-2-(1′-cyclohexenyl)ethyl-acetamides/benzamides. The reaction was catalyzed by in situ generated trimethylsilyl iodide and featured by its very short reaction time. The starting materials were easily obtained by the condensation of substituted acetic/benzoic acids with 2-(1′-cyclohexenyl)ethyl amine.     

Photochromic characteristics of spirocyclic organic and coordination compounds

Methods for the structural modification of photochromic spirocyclic systems (derivatives of spirobenzopyrans, spiro-1,3-oxazines, spiropyrimidines, and the bischelate complexes of nontransition metals), optimizing their spectral, kinetic, photochemical, and other characteristics in the direction required for their application as quick-acting chemical memory elements and in optical computers, are examined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 3, pp. 166–180, May–June, 1995.     

1,3-Dipolar Activity in Cycloadditions of an Aliphatic Sulfine(,)(1)

2,2,4,4-Tetramethyl-3-thioxocyclobutanone S-oxide (4) combines with diaryl thioketones at room temperature furnishing spiro-1,2,4-oxadithiolanes 6 in equilibrium reactions. Compound 6a was oxidized to the cis-S,S-dioxide 9, the structure of which was established by X-ray analysis. These are the first unequivocal 1,3-cycloadditions of thione S-oxides (sulfines) which possess an allyl anion type MO; cycloadditions to the C=S bond of sulfines as dipolarophile and dienophile had been described before.     

Synthesis of spiro-1-pyrazolines by the 1,3-dipolar cycloaddition of exocyclic α,β-unsaturated ketones with diazomethane

1,3-Dipolar cycloadditions of exocyclic α,β-unsaturated ketones 1-22 with diazomethane afforded spiro-1-pyrazolines 23-44 in a diastereospecific reaction. The structure and stereochemistry of each compound synthesised has been elucidated by nmr spectroscopic measurements and other analytical techniques. It has been proven that the stereochemistry of the starting α,β-enones was retained in the course of these cycloadditions.     

Synthesis of Some Spirooxazolidinones

In this communication, we wish to report the synthesis of some new spiro-4-oxazolidinones. Treatment of the potassium salt of 2-methyl-cyclohexane-1,3-dione (1) with α-chloroacetanilides (2 a-c) gave 4-aryl-6-methyl-1-oxa-4-aza-spiro [4,5] deca-3,7-diones (3 a-c); and with α-halopropionanilides (2 d,e), the corresponding 4-aryl-2,6-dimethyl-1-oxa-4-aza-spiro [4,5] deca-3,7-diones (3 d, e) were obtained.     

Reactions of polymerization-resistant 1,2-dithiolanes with lithiated oxygen heterocycles

Lithiated furans have been found to cleave the S–S bond of polymerization-resistant 1,2-dithiolanes to give the ring opened products in good yields. In the case of lithiated benzofuran, the excess reagent reacted with the normal product to give a mixture. Lithiated dihydrofuran and dihydropyran gave the corresponding ring-opened products that rearranged to spiro-1,3-dithianes during acidic workup. The reaction was applied to the selective synthesis of substrates for intramolecular Diels-Alder reactions. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:281–287, 1998     

Semiempirical calculation on photochromic process of spirooxazines

Structure effect on photochromic mechanism of 1,3-dimethyl-3,2′-(1,3-propyl-ene)spiro-[indoline-2,3′-[3H]naphtho[2,1-b][1,4]oxazine] (SP1) and 1,2′-(1,3-propylene)-3,3-dimethylspiro[indoline-2,3′[3H]naphtho[2,1-b]-[1,4]oxazine] (SP2) has been studied by AM1 calculation. The colored forms of SP1 and SP2 were fully optimized by AM1 method, and the results support the keto structures. The calculation results on stability of colored forms are agreeable with published experimental results.