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Hünlich's base modification has resulted in introducing a series of versatile Λ-shaped building blocks presented in this work. The methods are optimized to provide convenient approaches in the quicker production of these new building blocks in low-cost and low-risk. [ABSTRACT FROM AUTHOR]

A route to the oxabicyclic cores of the HIV cytoprotective quinolone alkaloids, waltheriones C and D, is described. The approach relies on a stereospecific transannular bromoetherification followed by reductive debromination. The route can also be rendered enantioselective via enzymatic reduction of a key intermediate (>99:1 er). [ABSTRACT FROM AUTHOR]

In 2014, more than 80% of the marketed drugs in the US contained heterocyclic compounds, which play a major role in the drugdiscovery process, as one of the primary components. Benzoxazole, consisting of an oxazole ring fused with a benzene ring, has shown profound impact in drug discovery research owing to its important bioactivity. This moiety has also shown important properties in material science. The synthesis of this privileged scaffold from readily available chemicals remains a primary focus for the synthetic chemistry community. In this review, efforts have been made to focus on the latest information available on the different synthetic strategies such as solution phase, multicomponent, green and solid phase chemistry and applications of different benzoxazole derivatives. Furthermore, the updated synthetic information incorporated in this review article will help to improve future synthesis of this scaffold. 1 Introduction 2 Solution-Phase Synthetic Approach to Substituted Benzoxazoles 2.1 Condensation of o-Aminophenol with Carboxylic Acids 2.2 Condensation of o-Aminophenol with Aldehydes 2.3 Condensation of o-Aminophenol with Orthoesters, ortho-Haloamides, or 1,1-Dihaloalkenes 2.4 Synthesis of Benzoxazoles from Schiff Bases 2.5 Miscellaneous 3 Multicomponent Synthetic Approach to Substituted Benzoxazoles 4 Solid-Phase Synthetic Approach to Substituted Benzoxazoles 5 Green Synthetic Approach to Substituted Benzoxazoles 5.1 Condensation of o-Aminophenol with Aldehydes 5.2 Condensation of o-Aminophenol with ortho-Substituted Benzamides 5.3 Condensation of o-Aminophenol with Carboxylic Acid and its Derivatives 5.4 Condensation of o-Aminophenol with Alcohols or Amines 5.5 Miscellaneous 6 Bioactive Derivatives of Benzoxazoles 7 Conclusion and Outlook. [ABSTRACT FROM AUTHOR]

Toward the total synthesis of acremoxanthone A, a model study has revealed a convergent approach to construct the ABCDE ring system. The key steps include: (1) an effective construction of the bicyclo[ 3.2.2]nonane skeleton, (2) protocol for generating the bridgehead anion and trapping, and (3) 1,3-dipolar cycloaddition of a nitrile oxide to the internal alkene. [ABSTRACT FROM AUTHOR]

The reduction of bicyclic tetramates can be achieved with high levels of diastereocontrol, but small changes in the substitution of the bicyclic lactam system can lead to changes in the steric bias of the concave/convex system. The tetramates and pyroglutamates prepared in this work exhibited limited antibacterial activity. [ABSTRACT FROM AUTHOR]

A facile approach for the stereoselective synthesis of a- and b-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid is described. Substrate- controlled α-carboxylation of norbonene monoester delivered the asymmetric diester intermediate with high diastereoselectivity (up to 35:1). Sequential chemoselective ester cleavage, Curtius rearrangement, and hydrolysis gave the a- and b-isomers of 2-aminobicyclo[ 2.2.1]heptane-2-carboxylic acid, respectively. [ABSTRACT FROM AUTHOR]

Bicyclo[3.2.1]octane systems carrying an (R)-carvone core were successfully constructed by 5-exo-cyclization between a β-keto ester function and a 3,3-dimethylallyl group under oxidative radical conditions. [ABSTRACT FROM AUTHOR]

The copper-catalyzed hydro- and carboboration of strained alkenes is presented. The reaction is highly diastereoselective and affords boronic ester derivatives many of which are difficult to synthesize by known methods. Competition experiments with different alkenes show that high levels of chemoselectivity can be achieved. Density functional theory calculations are in agreement with the observed chemoselectivity. [ABSTRACT FROM AUTHOR]

This account summarizes our recent work on palladacycles in organic synthesis and describes some unique catalytic properties of palladacycles as transition-metal catalysts for some useful transformations. Asymmetric induction has been realized by using chiral palladacycles as transition-metal catalysts. The influence of the C-Pd bond of palladacycles on their catalytic activity has been revealed. The reaction selectivity can be switched by appropriate choice of an sp2- or sp3-hybridized CP-palladacycle catalyst. 1 Introduction 2 The Discovery of the Use of Palladacycles as Transition-Metal Catalysts and Their Applications in Asymmetric Catalysis 3 Switch Between Addition and Ring Opening in the Reaction of Oxabicyclic Alkenes with Terminal Alkynes by Catalysis with sp2-CP- or sp3-C,P-Palladacycles 4 Synthesis of Polysubstituted Furans, Methylenecyclopropanes, and Polycyclic 5H-Benzo[b]azepines through Catalysis by Palladacycles 5 Conclusions [ABSTRACT FROM AUTHOR]

An approach to a model compound for polycyclic polyprenylated acylphloroglucinols is developed using a ring-closing metathesis approach to give a substituted cyclooctene. This undergoes cyclization via an intramolecular acylation leading to a substituted bicyclo[3.3.1]nonan-9-one related to hyperforin, nemorosone, clusianone, garsubellin A and other members of the polyprenylated acylphloroglucinol. [ABSTRACT FROM AUTHOR]

This account describes the developments on the synthesis and reactivity of functionalized 2,8-diheterobicyclo[3.2.1]octanes. The continued interest in the chemistry of these compounds is mainly due to their abundance in Nature, being at the core of numerous families of biologically active natural products, and also as a result of their versatile reactivity, which makes them very useful building blocks with considerable impact in modern organic synthesis. The present article is aimed toward providing a comprehensive coverage of the literature on these heterocyclic scaffolds, including our own contributions, and has been organized according to the nature of the heteroatom embedded in the 2,8-bicyclo[3.2.1]octane framework. [ABSTRACT FROM AUTHOR]

N-(1,7-Dioxotetrahydropyrazolo[1,2-a]pyrazol-2-yl)- benzamide derivatives, a novel class of compounds, were synthesized by 1,3-dipolar cycloaddition of azomethine imines with azlactones and subsequent rearrangement. The reaction can be completed rapidly under mild conditions without a catalyst. [ABSTRACT FROM AUTHOR]

N-(3-Hydroxypropyl)-2-nitro-N-(ω-phenylalkyl)acetamides underwent intramolecular cyclization in triflic acid to afford the corresponding hydroxyimino six- to nine-membered benzofused lactams. The six-membered derivative slowly transformed into 2- (3-hydroxypropyl)isoquinolin-3-one. NMR spectroscopic analysis in situ provided information on the cationic species involved in the reaction, permitting a mechanism to be postulated. This reaction provides a novel and simple route to benzofused lactams. [ABSTRACT FROM AUTHOR]

Functionalized octahydroindoles were synthesized from (±)-cyclohex-2-en-1-ol as potential intermediates for convergent syntheses of several alkaloids from plants of the Daphnyphyllum genus. [ABSTRACT FROM AUTHOR]

A highly stereoselective annulation reaction of 2-cyano-2-cycloalkenones with the Nazarov reagent catalyzed by 1,8-diazabicyclo[ 5.4.0]undec-7-ene (DBU), leading to densely functionalized bicyclic systems, is developed. [ABSTRACT FROM AUTHOR]

A scalable synthesis was developed of 3,5-methanonipecotic acid (3-azabicyclo[3.1.1]heptane-1-carboxylic acid), a rare example of a conformationally constrained nonchiral β-amino acid, potentially useful in peptide engineering and peptidomimetic drug design. A retrosynthetic strategy based on disconnections exclusively within the symmetry planes of the target and the intermediate molecules was found to be useful and might deliver expedite syntheses in other similar cases. [ABSTRACT FROM AUTHOR]

One of the main challenges that organic chemists face is the development of new ways to obtain novel compounds in a fast, clean, and efficient manner. Among the strategies developed to achieve this goal are multicomponent and tandem reactions, which offer the opportunity of building up complex molecules from simple starting materials in a single synthetic operation. Alkynol derivatives are one example of these simple starting materials which, combined with other appropriate reagents, are easily transformed into interesting final products. The explosion of research that has occurred in recent years in the field of gold catalysis has served to further raise the value of alkynol derivatives as useful materials for multicomponent and cascade reactions. This account describes our recent work in this area and shows how simple reagents can be catalytically converted into complex molecules containing interesting motifs, such as eight-membered rings, [3.3.1]- and [3.2.1]-bicyclic compounds, quinolines, and spiroacetals. In addition, the application of the methods developed is shown in the total syntheses of some natural products, such as berkelic acid. [ABSTRACT FROM AUTHOR]

A sugar aldehyde with silyl protection at C1, readily prepared from methyl α-D-glucopyranoside, reacted with allylborate or allylchromium reagents to afford the corresponding (anti) adducts, which were selectively converted into either E- or Z-diene. Deprotection of the anomeric position with TBAF proceeded in excellent yield, and further functionalization of the resulting hemiacetal led to the formation of complex bicyclic products such as highly functionalized oxazolidines. [ABSTRACT FROM AUTHOR]

An efficient tandem [3+2] cycloaddition-elimination cascade sequence has been developed enabling assembly of the pharmacologically relevant pyrrolo-[3,4-c]pyrrole-1,3-dione chemotype. The strategy involves simple mixing of readily accessible oxazolin-2-ones and pyrrole-2,5-diones in the presence of base under mild conditions, rendering the title compounds in typically excellent yields. Of note, this route allows for installation of three points of diversity and is ideal for combinatorial applications and parallel synthesis production campaigns. [ABSTRACT FROM AUTHOR]

Octahydropentalene 2,5-disulfonic acid was prepared in five steps as a single stereoisomer from the corresponding bicyclic diketone. The latter was first reduced followed by activation of the secondary-alcohol functions and nucleophilic substitution with thioacetate. The thioester moieties were oxidatively degraded to the bischlorosulfonyl derivative. On this stage the configuration was established by a X-ray single-crystal analysis. Hydrolysis gave the target compound as the trihydrate. [ABSTRACT FROM AUTHOR]

A facile method of synthesis of 4H-pyrazino[1,2-a]- pyrimidine-4,9(8H)-diones and imidazo[1,2-a]pyrazin-8(7H)-ones from the corresponding 3-amino-2(1H)-pyrazinones is described. [ABSTRACT FROM AUTHOR]

A method to derive functionalized biquinoline- and quinoline- bearing chromene bicyclic systems through aryl-aryl bond formation in a one-pot synthesis is described. The X-ray structure analysis provides insight into the mode of orientation of the molecules and opens the way to the synthesis of various hybrid molecules by making use of suitable substituents at R1, R2, and R3. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed cyclization of cyclopropylsubstituted 1,6-enynes proceeded in two ways depending on the presence or absence of a leaving group. In the presence of the leaving group, 5.7-bicyclic trienes were obtained as the sole products; in the absence of the leaving group, monocyclic trienes were isolated. [ABSTRACT FROM AUTHOR]

In this account we have systematically described the acid-promoted intramolecular cycloadditions of activated cyclo­propanes, which were conceptually classified into intramolecular cross-cycloadditions (IMCC) and intramolecular parallel-cyclo­additions. The IMCC provided a general and efficient strategy for construction of structurally complex and diverse bridged bicyclic skeletons. The potential of this strategy has been demonstrated by the synthesis of natural products.1 Introduction2 [3+2]IMCC of Cyclopropane 1,1-Diester with C=O3 [3+2]IMCC of Cyclopropane 1,1-Diester with C=N4 [3+2]IMCC of Cyclopropane 1,1-Diester with C=C5 [3+3]IMCC of Cyclopropane 1,1-Diester with Nitrones6 [3+2]IMCC of Mono-donor/Mono-acceptor Cyclopropane with C=O7 Lewis Acid Regulated Domino Cycloisomerization/[4+2]IMCC or [3+2]IMCC of Alkynylcyclopropane Ketone with C=O and C=N8 Conclusions and Outlook [ABSTRACT FROM AUTHOR]

An operationally simple and highly effective annulation process, making use of ZnCl2-catalyzed Michael addition and K2CO3/NaI-induced cyclization as key manipulations, has been developed to construct various bicyclic systems with a high level of functionalization valuable for further synthetic elaboration. [ABSTRACT FROM AUTHOR]

The preparation of 5-substituted 2,3-methanopyrrolidines by the stereoselective cyclization of zincated α-amino nitriles derived from enantiopure α-branched homoallylamines has been investigated. The formation of trans adducts in excellent diastereoselectivities (up to >98:2) and good yields (up to 71%) is observed. The absolute configuration and enantiomeric excess are dependent on the nitrogen protecting group. [ABSTRACT FROM AUTHOR]

An array of tetrasubstituted saturated fused pyrimidines has been synthesized through two-sequential, simple, and efficient one-pot operations. The strategic utilization of the N-PMB group proved critical in the ability to construct a broad range of N-vinyl tertiary enamide starting materials. This stands as a flexible approach to functionalized pyrimidines with the capability of manipulating either ketone, acid chloride, or nitrile reaction partners. [ABSTRACT FROM AUTHOR]

A copper(II)-catalyzed reaction of α-azido-N-allylamide synthetic under an oxygen atmosphere resulted in the formation of 2-formyl pyrazinones. The present transformation was characterized by the following steps: 1) 1,3-dipolar cycloaddition of the azido part onto the intramolecular alkene to give bicyclic aziridine intermediates; 2) further copper(II)-catalyzed oxygenation-oxidation of the aziridines to give 2-formyl pyrazinones. [ABSTRACT FROM AUTHOR]

An improved two-step synthetic approach towards 3-(2-chloroethyl)cyclobutanone is described and used in the synthesis of a class of 2-alkyl-2-azabicyclo[3.1.1]heptane-1-carbonitriles. The key step consists of a reversible addition of hydrogen cyanide onto the in situ generated imines, followed by an intramolecular nucleophilic substitution, thereby leading to the bicyclic skeleton in moderate to good yields (47-92%). These bicyclic compounds are stable, and the incorporated cyano group can be easily reduced to the corresponding aminomethyl group in high yields (93-99%), using lithium aluminum hydride. [ABSTRACT FROM AUTHOR]

Cycloaddition and cycloisomerization based on the interaction between an allene and another multiple bond, such as an alkyne, alkene, or additional allene, enabled us to build a variety of useful cyclic structures. This account describes our research on allene cycloaddition and cycloisomerization, categorizing the reactions by the proper reaction mode and the cyclic framework of the product. 1 Introduction 2 Construction of Bicyclo[m.3.0] Skeletons via Carbonylative [2+2+1] Cycloaddition 2.1 From Allene-Ynes and Aza Analogues 2.2 From Allene-Enes 2.3 From Bis-allenes 3 Construction of Bicyclo[m.2.0] Skeletons via [2+2] Cyclo�addition 3.1 From Allene-Ynes 3.2 From Bis-allenes 4 Construction of Bicyclo[4.4.0] Skeletons via 6π-Electrocyclization/[4+2] Cycloaddition 5 Construction of Monocyclic Polyenes via Cycloisomerization 5.1 From Allene-Ynes 5.2 From Allene-Enes 5.3 From Bis-allenes 6 Construction of Bicyclo[5.m.0] Skeletons via [5+2] Cyclo�addition 7 Conclusions and Outlook [ABSTRACT FROM AUTHOR]

A chemoselective Dieckmann ring closure using an oxazolidine derived from serine may be used to generate a tetramic acid, the further manipulation of which by reduction and ring closure leads to the bicyclic core of isatisine; depending on the nature of the ring closing electrophile, different diastereomers are obtained. None of the compounds from this sequence exhibited activity against S. aureus but several showed activity against E. coli. [ABSTRACT FROM AUTHOR]

A novel rearrangement pathway of 3-alkoxycarbonyl-4-carbamoylisoxazolidines, leading to 1H-pyrrole-2,5-diones by treatment with TBAF, is reported. DFT quantum chemical calculations support the reaction route, controlled by ring strain, which proceeds through the opening of a bicyclic intermediate, with aldehyde extrusion. [ABSTRACT FROM AUTHOR]

A simple and efficient copper-catalyzed method has been developed for synthesis of bicyclic pyrimidinones containing six-, seven-, eight-membered rings under mild conditions. The protocol uses readily available 2-bromocycloalk-1-enecarboxylic acids, amidines, and guanidines as the starting materials, copper-catalyzed cascade couplings provide the corresponding bicyclic ?pyrimidinones without addition of any ligand or additive, and the method is of economical and practical advantages. [ABSTRACT FROM AUTHOR]

Michael-type addition of enamino esters to 3,4,6-tri- O-benzyl-2-nitro- D-glucal under solvent-free conditions formed C-glycosides in excellent yields with high stereoselectivity. Reduction of the nitro group afforded the corresponding bicyclic 2-amino C-glycosides. [ABSTRACT FROM AUTHOR]

Recent work on synthetic applications of bicyclic al�kenes is reviewed, including synthesis of substituted bicyclic al�kenes, 1,3-dipolar cycloadditions, ruthenium-catalyzed [2+2] cycloadditions, ruthenium-catalyzed cyclizations and isomerizations, rhodium-catalyzed dimerizations, ruthenium- and rhodium-catalyzed ring-opening reactions. 1 Introduction 2 Synthesis of Substituted Norbornadienes and Norbornenes 2.1 Synthesis of 2- and 2,3-Disubstituted Norbornadienes by Double Lithium-Halide Exchange 2.2 Synthesis of Norbornadiene-2,3-diynes by Palladium-Catalyzed Sonogashira Coupling Reactions 2.3 Synthesis of 2,3-Diarylnorbornadienes by Palladium-Catalyzed Suzuki Coupling Reactions 2.4 Synthesis of Substituted Bicyclic Alkenes by Iron-Catalyzed Coupling Reactions 3 1,3-Dipolar Cycloadditions of Bicyclic Alkenes 3.1 Intramolecular 1,3-Dipolar Cycloadditions of Norbornadiene-Tethered Nitrile Oxides 3.2 Intramolecular 1,3-Dipolar Cycloadditions of Norbornadiene-Tethered Nitrones 4 Ruthenium-Catalyzed [2+2] Cycloadditions of Bicyclic Alkenes 4.1 Reactivity of the Alkene and the Alkyne Components 4.2 Heteroatom-Substituted Alkynes 4.3 Regioselectivities 4.4 Asymmetric Induction Studies 5 Ruthenium- and Rhodium-Catalyzed Reactions of Heterobicyclic Alkenes 5.1 Ruthenium-Catalyzed Cyclization Reactions of Oxabenzonorbornenes with Propargylic Alcohols 5.2 Ruthenium- and Rhodium-Catalyzed Isomerizations and Dimerizations of Oxabenzonorbornenes 5.3 Ruthenium- and Rhodium-Catalyzed Ring-Opening Reactions of 3-Aza-2-oxabicyclo[2.2.1]hept-5-enes 6 Conclusions [ABSTRACT FROM AUTHOR]

Annulated analogues of 5,6-dihydroxypyrimidine-4-carboxylate ester and 5,6-dihydroxypyrimidine-4-carboxylamide were synthesized. The intermediary homoallylic amines were subjected to a ring-closure reaction under different reaction conditions. A notable pH-dependency of the ring closure leading to regioisomeric tetrahydropyrrolo[1,2-a]pyrimidines was observed. Treatment with dimethyldioxirane and base led to 3-hydroxy-4-oxo-4,6,7,8-tetrahydropyrrolo[1,2-a]pyrimidines while m-chloroperbenzoic acid or NBS afforded 3-hydroxy-2-oxo-2,6,7,8-tetrahydropyrrolo[1,2-a]pyrimidines. [ABSTRACT FROM AUTHOR]

An efficient approach to the synthesis of azaspiro compounds having dissymmetric dienone cores was achieved by IPSO-iodocyclization of ethoxyethyl ether to alkynes. When the linker was an ether or an ester, domino iodocyclizaion/Diels-Alder reaction proceeded to afford the dimer, which can be transformed into the bridgehead-spiro connection ring system by a domino retro-?Diels-Alder/Diels-Alder process. [ABSTRACT FROM AUTHOR]

A reversible donor-acceptor fluorescence redox switch connected by a rigid but redox-adjustable spacer that can be chemically turned ON and OFF through the ring opening and ring closing of a heterobicyclic moiety is demonstrated. A coumarin-based oxazabicyclic derivative was efficiently synthesized as an example for illustration. While the rigid ring-closed oxazabicycle emits moderate fluorescence in toluene, the sodium borohydride induced ring opening of the heterobicyclic moiety results in a distinct decrease in fluorescence. The resulting nonfluorescence ring-opened form can be reverted to the original fluorescence ring-closed form via DDQ or H 2O 2oxidation. [ABSTRACT FROM AUTHOR]

A batchwise, multigram preparation of 2-azabicyclo- [2.1.1]hexane hydrochloride (1·HCl) was developed, delivering a total of 195 grams of material. The key synthetic step involves an intramolecular displacement of a primary alkyl chloride with a tert-butylsulfinamide to forge the [2.1.1]-bicyclic ring system. [ABSTRACT FROM AUTHOR]

The first DABCO-induced [2+2+2]-cycloaddition reaction of ethyl propiolate and aryl aldehydes is reported for selectively constructing 4-aryl-4 H-pyrans in moderate to good yields. [ABSTRACT FROM AUTHOR]

Bi- and tricyclic 9-oxabispidines are smoothly deprotonated at -78 ˚C by s-BuLi at one of the bridgehead carbon atoms to give α-lithio ethers, which were trapped with electrophiles in good yields. Rearrangements to ring-contracted N,O-acetals occurred upon warming in the absence of an electrophile. The α-lithio ether intermediates are presumably stabilized by negative hyperconjugation. [ABSTRACT FROM AUTHOR]

A formal total synthesis of (-)-didemniserinolipid B from L-(+)-tartaric acid is presented. Key features of the synthesis include construction of the bicyclic acetal core from bisdimethyl amide of tartaric acid and further elaboration by cross metathesis. [ABSTRACT FROM AUTHOR]

Synthesis of new thiazolidine-fused five-, six-, and seven-membered heterocycles through vinylogous N-acyliminium ion-cyclization sequence, involving positions 3 and 4 of the thiazolidine ring, is described. The formation of bicyclic products, arising by generally disfavored 5- ENDO-trig cyclization initiated by sulfur atom acting as a nucleophile, indicates the preparative value of this method. [ABSTRACT FROM AUTHOR]

We report the first example of the Claisen rearrangement in the 2-[( Z)-alkenyl]dihydropyran system yielding spiro[4.5]decane in a TRANS fashion. This protocol is useful for the synthesis of TRANS-substituted spiro[4.5]decanes, a potentially useful class of spirocyclic terpenes and alkaloids. [ABSTRACT FROM AUTHOR]

The conjugate addition of activated propargylic alcohols to alkyl propiolates is shown to be catalyst-dependent. Whereas trialkylamines catalyze the expected 1,4-adition of the alcohol on the alkynoate to give the β-alkoxyacrylate derivative, the trialkylphosphine-catalyzed reaction affords densely functionalized bicyclic hexahydrofuro[2,3-b]furan derivatives. A mechanistic proposal for the phosphine-catalyzed addition of alcohols to alkyl propiolates according with these observations is presented. [ABSTRACT FROM AUTHOR]

The use of a commercially available thiazolium salt facilitated an intramolecular Stetter reaction between an aliphatic aldehyde and an acrylate unit, which delivered a TRANS, SYN-fused bicyclic pyranone in high yield as a single diastereomer. The pyranone was used to synthesize a TRANS, SYN, TRANS-fused polycyclic ether array and was ring expanded to give the corresponding oxepanone. [ABSTRACT FROM AUTHOR]

Microwave-assisted, solvent-free condensation of 2-aminopyrimidine with aldehydes and isonitriles gave the desired 3-aminoimidazo[1,2-a]pyrimidine products with good to excellent regioselectivity. A hydrogen zeolite (‘zeolite HY’) was found to be a novel and effective promoter for the reaction, generally leading to clean conversion and also permitting use of the normally unreactive 4,6-dimethyl-2-aminopyrimidine. [ABSTRACT FROM AUTHOR]

The intramolecular nitrile oxide-alkene cycloaddition has been studied in an enediyne system. It has been shown to be an efficient method for one-step synthesis of isoxazoline-fused bicyclic enediynes. The thermal reactivity of these enediynes is similar to the isoxazolidine-fused counterparts, thus ruling out any significant effect by the bridgehead double bond. [ABSTRACT FROM AUTHOR]

Upon treatment with DAST (diethylaminosulfur trifluoride) enantiopure 2-hydroxyalkylazetidines rearrange into 3-fluoropyrrolidines. The reaction is stereospecific and involves a bicyclic 1-azoniabicyclo[2.1.0]pentane intermediate which is regioselectively opened by a fluoride anion. [ABSTRACT FROM AUTHOR]

3-Bromo-2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl was reacted with several C-nucleophiles to give novel bicyclic pyrrolidine nitroxides through partial Favorskii rearrangement. Further reduction with sodium borohydride gave spin probes with free hydroxyl groups and under harsh reduction conditions allowed the Favorskii rearrangement to proceed to completion. [ABSTRACT FROM AUTHOR]