N-azirin-3-yl and N-indol-3-yl azaxylylenes

Flash-vacuum pyrolysis of N-(2,3-diphenylazirin-3-yl)dihydrobenzoxainones leads to transient N-azirinyl- and N-indolylazaxylylenes which give 2-arylindoles (5) and dihydroindoloquinolines (8) respectively. 5H-1,4-Benzodiazepines are implicated as the precursors to the indoles via the methylene nitrile ylides (9) and an alternative route to the latter by flash pyrolysis of N-(2-methylphenyl)benzimidoyl chlorides (10) provides a new, simple route to 2-arylindoles.     

Generation and reactions of a selenoamide dianion

The selective generation of selenoamide monoanion and dianion was achieved by reacting N-benzyl selenobenzamide with BuLi. Alkylation of the dianion with 1 equiv of electrophile took place at the carbon atom adjacent to the nitrogen atom, and subsequent hydrolysis produced functionalized selenoamides in good to high yields. Ring opening of oxiranes using the dianion proceeded with high regio- and stereoselectivity to form N-3-hydroxy-1-phenylalkyl selenobenzamides. The stereochemistry of the major isomer derived from cyclohexene oxide was determined by X-ray molecular structure analysis. [reaction: see text]     

Generation and intermolecular reactions of 3-indolylacyl radicals

The generation of 3-indolylacyl radicals from the corresponding phenyl selenoesters and the scope of their participation in intermolecular addition reactions to carbon-carbon double bonds under both reductive and nonreductive conditions have been studied.     

Generation and reactions of 2-alkyl-3-carboethoxycyclopentadienones

Thermolysis of 6-alkyltricyclo[5.2.1.0^2,6]decadienone esters 3 in DMF produces 2-alkyl-3-carboethoxycyclopentadienones 8 in an efficient [4+2]cycloreversion reaction. These cyclic dienones can be trapped by cyclopentadiene to afford regioselectively tricyclodecadienones 9 in high yields.     

Generation and cycloaddition reactions of indole-2,3-quinodimethanes

N-methyl and N-tert-butoxycarbonylindole-2,3-quinodimethanes ($\text{2}$ and $\text{3}$) have been generated and observed to undergo intermolecular cycloaddition reactions with dienophiles.     

Generation and intermolecular reactions of 2-indolylacyl radicals

The generation of 2-indolylacyl radicals from the corresponding phenyl selenoesters, aldehydes, and alpha-keto carboxylic acids and the scope of their participation in intermolecular addition reactions to carbon-carbon double bonds have been studied. Whereas the phenyl selenoester method has provided easy access to a variety of 1,4-dicarbonyl compounds bearing the 2-acylindole moiety, the glyoxylic acid route has been employed for the preparation of 2-indolyl pyridyl ketones.     

Generation and consumption rates of OH radicals in sonochemical reactions

In this study, a KI aqueous solution or Methyl Orange (MO) aqueous solution was irradiated by an ultrasonic wave under the same experimental condition. The rates of oxidation of KI and MO by OH radicals differed by an order of magnitude. When the consumption of OH radicals by chemical reactions with species other than KI or MO is taken into account, numerical analysis of chemical kinetics model yields the same generation rate of OH radicals by the action of an ultrasonic wave for the experiments of KI and MO solutions.     

Generation and electrophilic substitution reactions of 3-lithio-2-methyleneaziridines

2-Methyleneaziridinyl anions can be produced by selective deprotonation of the parent aziridine at C-3 using sec-BuLi/TMEDA. Subsequent reaction with a wide variety of electrophiles including MeI, ICH₂CH₂CH₂CH₂Cl, PhCH₂Br, allyl bromide, Me₃SiCl, Bu₃SnCl, PhCHO and Ph₂CO provides the corresponding C-3 substituted derivatives in moderate to good yields (43-91%). In the case of homochiral methyleneaziridines bearing an (S)-α-methylbenzyl group on nitrogen, high levels of diastereocontrol (up to 90%de) can be achieved in this lithiation/alkylation sequence.     

Generation and carbonyl addition reactions of Z-dilithiohex-3-ene-1,5-diyne

The reaction of the title dilithio salt with carbonyl compounds leads to products bearing substructures found in recently discovered enediyne antibiotics. The bis condensation product with benzaldehyde undergoes a novel cycloaromatization reaction.     

Generation of model reactions leading to limit cycle behavior

The system of differential equations by Feistel and Ebeling has been generalized. Some new formal kinetic reactions with two internal components, which may exhibit limit cycle behavior have been studied. Based upon the numerical integration of the deterministic models of these reactions the oscillatory character of the systems has been confirmed.

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Generation and reactions of novel oxiranyl ‘Remote’ anions

Deprotonation of an oxiranyl β-proton takes place in a stereoselective manner providing the corresponding oxiranyl ‘remote’ anion. The anion is stabilized by chelation between the lithium and the carbonyl moiety of an ester, lactone, imide, or keto-group in the form of a five-membered cyclic intermediate. Certain ester-stabilized oxiranyl anions are stable and can be left in THF solution at −78°C for several hours. The generated anions undergo a stereoselective alkylation reaction to provide products, which could be useful intermediates in the synthesis of bioactive naturally occurring α-methylene bis-γ-butyrolactones.     

Generation and reactions of oxiranyllithiums by use of a flow microreactor system

A flow microreactor system consisting of micromixers and microtubes provides an effective reactor for the generation and reactions of aryloxiranyllithiums without decomposition by virtue of short residence time and efficient temperature control. The deprotonation of styrene oxides with sBuLi can be conducted by using the flow microreactor system at -78 or -68 °C (whereas much lower temperatures (< -100 °C) are needed for the same reactions conducted under macrobatch conditions). The resulting α-aryloxiranyllithiums were allowed to react with electrophiles in the flow microreactor system at the same temperature. The sequential introduction of various electrophiles onto 2,3-diphenyloxiranes was also achieved by using an integrated flow microreactor, which serves as a powerful system for the stereoselective synthesis of tetrasubstituted epoxides.     

(2-Chlorovinyl)chlorocarbenes: Generation and reactions with alkenes

The treatment of Z-1,1,3-trichloro-4,4-dimethyl-2-pentene (Ia) with t-C₄H₉OK in boiling hexane or benzene gave rise to (Z-2-chloro-3,3-dimethyl-1-butenyl)chlorocarbene (IVa), which reacted with alkenes to give the cyclopropane derivatives (V) in 44–57% yields. Dichloro-(2-chloro-1-alkenyl)methanes (Ib-d), which have a hydrogen atom at the C₃ position of the alkenyl substituent, were also used as carbene precursors under these conditions. These compounds gave rise to mixtures of the cyclopropanes (VI)–(VIII) (obtained in up to 57% yields) and the dienes (IX)–(XI) (yields up to 54%). The reaction of cis-2-butene with (2-chloro-1-cyclopentenyl)chlorocarbene (IVd) was found to be completely stereospecific, indicating that this carbene exists in a singlet ground state.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2552–2558, November, 1991.     

Generation of 1-aryl-3-methoxycarbonylnitrilimines and their reactions with unsaturated hydrocarbons

Thermolysis of 1-(4-methoxyphenyl)- and 1-(4-fluorophenyl)heptamethoxycarbonyl-3a,7a-dihydroindazoles at 135?C140 °C resulted in the elimination of hexamethyl benzenehexacarboxylate and in the generation of 1-aryl-3-methoxycarbonylnitrilimines, which were trapped by alkenes and dienes to give the corresponding (1) pyrazolines via 1,3-dipolar cycloaddition and (2) 2-oxoalken-1-oic acid hydrazones via allylic proton migration to the nitrogen atom. The reaction with tetramethylethene unexpectedly yielded substituted 5-(1-hydroxy-1-methylethyl)- or 5-acetylpyrazolinecarboxylates as the main products. The formation of the latter compounds suggests initial abstraction of the H atom from tetramethylethene and probable participation of a water molecule that supplies one more oxygen atom to the reaction products.