Electrophilic cyclization of (E,E)-2-farnesylthiophene

Conclusions The electrophilic cyclization of (E, E)-2-farnesylthiophene has been studied for the first time, and it has been shown that the allylic thienyl group acts as a specific terminator which leads to the formation of a tetra cyclic molecule with a cis-hydrindane fragment.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1359–1362, June, 1981.Deceased.     

Copper iodide-catalyzed cyclization of (Z)-chalcogenoenynes

We present here our results of the efficient copper-catalyzed cyclizations of chalcogenoenynes and establish a route to obtain 3-substituted chalcogenophenes in good to excellent yields. In addition, the obtained chalcogenophenes were readily transformed to more complex products using the palladium-catalyzed cross-coupling reactions with boronic acids to give Suzuki-type products in good yields.     

A novel cyclization/oxidation strategy for a two-step synthesis of (Z)-aurone

An efficient and facile two-step strategy for the synthesis of (Z)-aurone from arylacetylenes and salicyladehydes, via silver(I) nitrate mediated cyclization/oxidation in the presence of potassium carbonate has been developed. The key feature of our method was delicate cascade reaction, to provide the corresponding (Z)-aurone in high yield and good regio- and stereo selectivity.     

Highly stereoselective synthesis of (Z)-3-methoxy-1-methyleneisoindoles via DMAP catalyzed cyclization of methyl 2-alkynylbenzimidates

A DMAP (4-dimethylaminopyridine) catalyzed cyclization of methyl 2-alkynylbenzimidates has been developed, which affords 3-methoxy-1-methyleneisoindoles with excellent Z-stereoselectivity under mild and transition-metal-free conditions. The (Z)-3-methoxy-1-methyleneisoindole products can be converted to corresponding 3-amino-1-methyleneisoindoles, 3-methoxy-isoindoles, 3-methyleneisoindolinones and isoindolinones with high efficiency.     

(Z,Z)-6,9-nonadecadien-3-one and (Z,Z,Z)-3,6,9-nonadecatriene: identification and synthesis of sex pheromone components of peribatodes rhomboidaria.

(Z,Z)-6,9-Nonadecadien-3-one and (Z,Z,Z)-3,6,9-nonadecatriene were identified by GC-EAD and GC-MS in ovipositor extracts of $\text{P}$. $\text{rhomboidaria}$; the synthetic mixture is attractive to males of the species in the field.     

Electrophilic cyclization of regular α-monoterpenols catalyzed by BF3 etherate

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 227–228, January, 1990.     

One-pot regioselective synthesis of chromanyl(phenyl)-lambda(3)-iodanes: tandem oxidative cyclization and lambda(3)-iodanation of 3-phenylpropanols

Reaction of 3-phenylpropanol with an activated iodosylbenzene-18-crown-6 complex [PhI(OH)BF4-18C6] in dichloromethane in the presence of BF3-Et2O afforded directly the 6-chromanyl(phenyl)-lambda3-iodane-18C6 complex through tandem oxidative intramolecular cyclization yielding chroman and its regioselective phenyl-lambda3-iodanation.     

Electrophilic cyclization of α- and β-geranyl acetates by mercury(II) trifluoroacetate

Electrophilic cyclization of β-geranyl acetate promoted by mercury(II) trifluoroacetate leads to mixtures of α- and γ-5αH-cyclogeranyl acetate derivatives and 6α-hydroxy-5αH-and 6α-hydroxy-5βH-cyclogeranyl acetate derivatives mercurated at the C-3 atom. The ratio of the unsaturated and hydroxymercurated products depends on the reaction conditions. α-Geranyl acetate reacts with mercury(II) trifluoroacetate to give a mixture of 6α-hydroxy-5αH-and 6α-hydroxy-5βH-geranyl acetates, mercurated at C-9, with an equatorial mercurated methylene group at C-4. The mercury-containing groups in mercurated cyclogeranyl derivatives can easily be reduced or replaced by an oxygen-containing functional group; this constitutes a convenient route to polyfunctional cyclogeranyl derivatives that are difficult to obtain. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1320–1324, July, 1997.     

Di(propargyl)nitramine: synthesis and reactivity

An improved synthesis of (propargyl)nitramine and its pioneering conversion to di(propargyl)nitramine involve the alkylation of NH nitramines with propargyl halides or tosylate as the key steps. The standard (p° = 0.1 MPa) molar enthalpy of formation at 298.15 K for di(propargyl)nitramine was determined from the experimental standard molar energy of combustion in oxygen, measured by static bomb combustion calorimetry. Propargyl nitramines are suitable substrates for 1,3-dipolar cycloaddition reactions with azides, nitrile oxides and diazo compounds.     

Electrophilic cyclization of 3-alkynyl-4-chalcogen-2-H-chromenes: synthesis of 3-halo-chalcogenophene[3,2-c]chromene derivatives

An efficient synthesis of 3-halo-chalcogenophene[3,2-c]chromene has been accomplished via electrophilic cyclization reaction of 3-alkynyl-4-chalcogen-2H-chromene using I₂, PhSeBr, and BuTeBr₃ as electrophilic sources. The cyclization reaction proceeded cleanly under mild reaction conditions, and 3-halochalcogen-chromenes were formed in good yields. In addition, the obtained 3-iodo-chalcogenophene-chromenes were readily transformed to more complex products using a metal-halogen exchange reaction with n-BuLi and trapping the lithium-intermediate formed with aldehyde, furnishing the desired secondary alcohol in good yield. Conversely, using the palladium catalyzed cross-coupling reactions with terminal alkynes and boronic acid, we were able to obtain the Sonogashira and Suzuki type products in good yields.     

Electrophilic reactivity of the dienyl ring in carbonylnitrosyl(cyclohexadienyl)manganese cations

A kinetic study is reported for the addition of phosphorus and nitrogen donor nucleophiles to the ring in (cyclohexadienyl)Mn(CO)(NO)L⁺ complexes (2, L = CO, PPh₃) to give cyclohexadiene complexes. It is shown that (i) the Mn(CO)(NO)L⁺ moiety is electronically equivalent to Fe(CO)₂L⁺ for activating a cyclohexadienyl ring and (ii) that a substituent (Me, Ph, CN) at the C(6)-saturated carbon in 2 produces a large steric retardation of the rate of nucleophile addition.     

Electrophilic reactivity of the dienyl ring in carbonylnitrosyl(cycloheptadienyl)manganese cations

A kinetic study is reported for the addition of phosphorus and nitrogen donor nucleophiles to the cycloheptadienyl ring in (C₇H₈R)Mn(CO)(NO)L⁺ complexes (3, R = H, Ph; L = CO, PBu₃) to give cycloheptadiene complexes (4). A substituent at the C(6) carbon in 3 does not produce any detectable steric effect, and the relative nucleophilic reactivities closely parallel those observed with other electrophilic organometallic and organic systems. The reaction 3 → 4 is the second step in the manganese-mediated conversion of a cycloheptatriene to a difunctionalized cycloheptadiene.     

Stereocontrolled synthesis of 3-alkylindolines from (Z)-2-hydroxyindolenines

Summary A convenient process for the synthesis of 3-alkylindolines2 and their transformation intocis-fused tricyclic -lactones3 from allylic alcohols1, mediated by aGrignard reagent, is described. This process proceeds with high stereocontrol at the two newly formed contiguous stereogenic centres. By oxidation with chromium oxide, 2-oxindole derivatives4 are obtained from 3-alkylindolines2.

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Stereokontrollierte Synthese von 3-Alkylindolinen aus (Z)-2-Hydroxyindoleninen

Zusammenfassung Eine einfache Methode zur Herstellung der 3-Alkylindoline2 und deren Umsetzung zu dencis-kondensierten tricyclischen -Lactonen3 aus den Allylalkoholen1 mittels einerGrignard-Verbindung wird beschrieben. Die Reaktion verläuft unter hoher Stereoselektivität bezüglich der zwei neu gebildeten Asymmetriezentren. Durch Oxidation mit Chromtrioxid erhält man aus den 3-Alkylindolinen2 die 2-Oxindolderivate4.

     

Gold-catalyzed cyclization of (Z)-2-en-4-yn-1-ols: highly efficient synthesis of fully substituted dihydrofurans and furans

[reaction: see text] The gold-catalyzed cyclization of (Z)-enynols offers an efficient and straightforward route to stereodefined (Z)-5-ylidene-2,5-dihydrofurans and fully substituted furans under extremely mild reaction conditions. Importantly, the results indicated that both the oxyauration and the proto-demetalation steps are highly stereoselective.     

Alpha-N-acetylmannosamine (ManNAc) synthesis via rhodium(II)-catalyzed oxidative cyclization of glucal 3-carbamates

[reaction: see text] Glucal 3-carbamates 1 and 7 underwent oxidative cyclization with iodobenzene diacetate or iodosobenzene in the presence of Rh2(OAc)4, providing mannosamine 2-N,3-O-oxazolidinones. With iodosobenzene, incorporation of 4-penten-1-ol provided a readily separable anomeric mixture of n-pentenyl glycosides, with the anomers exhibiting pronounced differences in reactivity as glycosyl donors. N-acylation of the sugar oxazolidinones led to alpha-selective glycosyl donors for the elaboration of various 2-mannosamine frameworks. Alternatively, the anomeric n-pentenyl glycosides of N-Cbz 2-mannosamine oxazolidinones were converted separately to oxazolidinone-opened derivatives 28alpha and 28beta. These served as stereoconvergent glycosyl donors, and the alpha-linked products were readily advanced to a variety of N-acetylmannosamine (ManNAc) frameworks, using an intramolecular O-->N acetyl transfer as the final step.     

1,3,4-Thiadiazines: Methods of synthesis and reactivity (review)

The synthetic methods for 1,3,4-thiadiazines and their intramolecular rearrangement reactions are reviewed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 435–448, April, 1991.     

Electrophilic cyclization of α-series monoterpene ω-derivatives

New information is discussed concerning the protic and Lewis acid-initiated electrophilic cyclization reaction of -monoterpenols and their acetates; the distinguishing feature of these reactions is their termination by isopropenyl residues in these molecules. The reactions have been found to be general in nature, given additional functionalization of the terminator by chloro-, sulfonyl, sulfonylmethyl, or ester substituents. Cyclization of these linear substrates has also been shown to provide a convenient method for the synthesis of dimethylvinylcyclohexene derivatives and related cyclohexanediols, which are not readily available by other methods.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1361–1367, June, 1990.     

Revisit to (Z)-civetone synthesis

The synthesis of (Z)-civetone (1) is described starting from oleic acid (5) via a series of reactions, intermolecular olefin self-metathesis, bromination/dehydrobromination into acetylene, semi-hydrogenation and intramolecular Dieckmann macrocyclization.     

Silver technology for stabilization of simple (Z)-enethiols: stereoselective synthesis and reaction of silver (Z)-enethiolates

Reported here for the first time are the stereoselective synthesis and reaction of simple silver (Z)-enethiolates, which serve as stabilized (Z)-enethiol storage. In contrast to labile enethiols, silver (Z)-enethiolates are stable even in solutions, and their isolation and purification are very simple. The method for synthesis of silver (Z)-enethiolates involves an unusual vinylic SN2 reaction of (E)-vinyl-lambda3-iodanes with thiobenzamides yielding the inverted (Z)-S-vinylthioimidonium salts, followed by their regioselective C-S bond cleavage with silver acetate. Alkylation, arylation, and Michael addition of silver (Z)-enethiolates yielding (Z)-vinyl sulfides were dramatically accelerated by the addition of Bu4NI (LiI), which probably generates reactive ammonium (Z)-enethiolates with an increased nucleophilicity.     

Gold(I)-catalyzed divergence in the reactivity of 3-silyloxy 1,6-enynes: pinacol-terminated vs claisen-terminated cyclization cascades

On activation with catalytic amounts of gold(I) complexes, 3-silyloxy 1,6-enynes can react through two alternative pathways. In one, a cascade reaction consisting of carbocyclization and subsequent pinacol rearrangement takes place. In the second pathway, a heterocyclization is followed by a Claisen rearrangement. The reaction outcome differs depending on the substitution pattern of the 3-silyloxy 1,6-enynes and, more importantly, the electronic properties of the gold-bound phosphane ligand.