Synthesis of Novel Ferrocenyl Oxindole and Ferrocene Substituted Dispiroheterocycles Through [3+2]Cycloaddition of Azomethine Ylides

Synthesis of novel ferrocenyl oxindoles was successfully achieved, and a series of novel dispiroheterocyclic system has been synthesized by the cycloaddition of azomethine ylides generated by the decarboxylative route from secondary amino acids (sarcosine/proline) and isatin/acenaphthequinone/ninhydrin with the newly synthesized ferrocenyl oxindole. All of the cycloaddition reactions gave ferrocenyl substituted pyrrolidine/pyrrolizidine derivatives with very high regio and stereoselectivity in reasonable yiels.     

Synthesis,Properties, and Special Features of the Fragmentation under Electron Impact of N-Substituted Nicotinoyl Ureas

A convenient preparative synthetic route has been developed and N’-substituted nicotinoyl ureas have been obtained for the first time. Possible directions have been studied for their fragmentation under electron impact.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 705–712, May, 2005.     

Efficient synthesis of methylenetetrahydrofurans and methylenepyrrolidines by formal [3+2] cycloadditions of propargyl substrates

Recent developments concerning the synthesis of methylenetetrahydrofurans and methylenepyrrolidines by one-pot formal [3+2] cycloadditions involving propargylic (and allylic) alcohols and amines with electrophilic alkenes are described. The synthetic methods provide powerful tools to prepare highly functionalized oxygen- and nitrogen-containing five-membered ring systems. The reactions can be effectively promoted by base, base/transition metals, and Lewis acids, depending on the substrates.     

A facile access to ureido sugars. Synthesis of urea-bridged β-cyclodextrins

The preparation of a urea-bridged β-cyclodextrin dimer and of a 6-monodeoxy-6-mono[3-(β-d-glucopyranos-2-yl)ureido]-β-cyclodextrin has been developed, using triphosgene as the isocyanation agent in an aqueous two-phase system. Per-O-acetylated β-d-gluco and mannopyranosylamines and 2-amino-2-deoxy-α- and β-d-glucose were also transformed into the corresponding isocyanates and converted in situ into ureas by coupling with aromatic and aliphatic amines.     

Synthesis of trans‐Fused Oxabicyclo[5.2.0]nonan‐2‐ones via [2+2] Photocycloaddition of Oxepinones to Conjugated Alkenes

On irradiation (350 nm) in the presence of 2,3‐dimethylbuta‐1,3‐diene, benzoxepinone 2 and dioxepinone 3 were converted regio‐ and diastereoselectively to trans‐fused oxabicyclo[5.2.0]nonanones 5 and 9 , respectively.     

[2＋2] Photocycloaddition of [60] Fullerene with Podophyllotoxin Derivative Containing Cyclohexadienone Group

Photochemical [2 2] cycloaddition of C60 with podophyllotoxin derivative containing a cyclohexadienone group in o-dichlorobenzene afforded an isomeric mixture of adducts and a pure adduct of C60-fused podophyllotoxin derivatives. The structures of the products were characterized by MS, NMR and IR spectra.     

Scope and Stereochemistry of [2+2] Photocycloadditions Between Cyclopentenones and 1,2-Dichlorocycloalkenes

Cyclopentenone and dichlorocycloalkenes give [2+2] adducts whose stereochemistry (from modern NMR) is mostly cis, anti, cis; cis, syn, cis minor adducts are also found. Cophotolysis of dichlorocyclohexene and cycloheptanocyclopentenone does not give any adduct.     

A stereocontrolled access to ring-fused piperidines through a formal [2+2+2] process

[reaction: see text] A formal [2+2+2] process has been devised that allows the stereocontrolled formation of ring-fused piperidines from allylsilanes possessing an oxime moiety. The cascade involves an intermolecular radical addition of an alpha-iodoacetate onto an allylsilane double bond, which is followed by a 5-exo-trig cyclization onto an oxime and is completed by the formation of the amide bond by nucleophilic attack of the amine onto the ester function.     

Synthesis of psudoheliotridane via formal [3+2] annulation and ring-closing metathesis

Base-induced coupling/cyclization stepwise [3+2] annulation of α-sulfonylacetamide with (Z)-2-bromoacrylates yielded polysubstituted pyroglutamates with three contiguous chiral centers with trans-trans orientation in a one-pot synthesis. The pyrrolizidine skeleton was obtained via the ring-closing metathesis (RCM) method. This facile strategy was used to synthesize psudoheliotridane.     

Synthesis of Thienyl‐Substituted Dihydrofuran Compounds Promoted by Manganese(III) Acetate

Radical cyclization reactions of both aliphatic 1,3‐diones 1a and 1b and of cyclic 1,3‐diones 1c – 1e with 2‐thienyl‐ and 3‐thienyl‐substituted alkenes 2a – 2d in the presence of manganese(III) acetate were investigated. Thienyl‐substituted dihydrofurans 3 were obtained with moderate to high yields (Table 1–3). Also, the favorable effect of the thienyl substituent on the intermediate carbocation stability was evaluated by comparison with a phenyl substituent.     

A Diastereoselective Synthesis of Functionalized Tetrahydroindeno[2′,1′,3,4]pyrido[2,1‐a]isoquinolines

An effective route to alkyl 9a‐(2,3‐dihydro‐1,3‐dioxo‐1H‐inden‐2‐yl)‐9a,14,14a,14b‐tetrahydro‐14‐oxoindeno[2′,1′:3,4]pyrido[2,1‐a]isoquinoline‐9‐carboxylates via a diastereoselective one‐pot four‐component reaction of isoquinoline and alkyl prop‐2‐ynoates with two equivalents of indane‐1,3‐dione, in aqueous MeOH at room temperature, is described.     

Enantioselective Intramolecular [2+2] Photocycloaddition Reactions of 4‐Substituted Coumarins Catalyzed by a Chiral Lewis Acid

Eight coumarins, which carry a terminal alkene tethered by a CH₂XCH₂ group to their 4‐position (X=CH₂, CMe₂, O, S, NBoc, NZ, NTs, NBn), were synthesized in overall yields of 51–80 %. Starting materials for the syntheses were either commercially available 4‐hydroxycoumarin or 4‐formylcoumarin. The intramolecular [2+2] photocycloaddition of these coumarins gave diastereoselectively products with a tetracyclic 3,3a,4,4a‐tetrahydro‐1H‐cyclopenta[2,3]cyclobuta[1,2‐c]chromen‐5(2H)‐one skeleton. Direct irradiation at λ=300 nm in dichloromethane (c=10 mM ) led to product formation in good yields for most substrates, presumably via a singlet excited state intermediate. Due to the low coumarin absorption at λ >350 nm the photocycloaddition was slow upon irradiation at λ=366 nm. Addition of a chiral oxazaborolidine‐based Lewis acid (50 mol %) increased the reaction rate at λ=366 nm and induced a significant enantioselectivity in the [2+2] photocycloaddition. Six out of eight coumarin substrates (X=CH₂, CMe₂, O, NBoc, NZ, NTs) gave the respective products in yields of 72–96 % and with 74–90 % enantiomeric excess (ee) upon irradiation in dichloromethane (c=20 mM ) at ?75 °C. The Lewis acid presumably acts by coordination to the coumarin carbonyl oxygen atom, which leads to a bathochromic shift (redshift) of the UV absorption and which increases the singlet state lifetime. A second electrostatic interaction of the hydrogen atom at C3 with the oxygen atom of the oxazaborolidine is likely.     

Retrospective View on Recent Developments in Cyclobutane Synthesis via [2+2] Photocycloaddition of Unsaturated Ketones to Acyclic Dienes

This synopsis addresses cyclobutane formation via light‐induced [2+2] cycloaddition from both cyclic and acyclic unsaturated carbonyl compounds, and 2,3‐dimethylbuta‐1,3‐diene