Regioselectivity in addition of atomic fluorine to alkenes

Irradiation of N₂F₄(NF₂) with propene and with 1,1-difluoroethene in the gas phase atroom temperature leads to the addition of F and NF₂ across the double bond. The ratioof terminal to internal addition of F to propene was found to be 1.4:1 after correctingfor the decomposition of vibrationally excited intermediates. In the case of 1,1-difluoroethene,the corrected ratio of F addition is 5:1 with addition at the methylene sitepredominating. The difference in selectivity of F addition to propene and to 1,1-difluoroethenecorrelates with spin density difference in the π-π* triplet state of the alkeneand with the difference in the HOMO coefficients of the substrate alkene, i.e. the patternof selectivity is that predicted by the State Correlation Diagram model of Shaik andCanadell.     

Regioselectivity and mechanism of dihalocarbene addition to benzocyclopropene

Dihalocarbenes add regioselectively to aryl-substituted benzocyclopropenes to produce dihalobenzocyclobutenes. The regioselectivity of addition is not due to steric effects but depends on the electronic donor or acceptor ability of the substituent. B3LYP/6-31G* calculations show preferential :CCl2 addition to substituted benzocyclopropene through electrophilic attack on the benzocyclopropene pi-system (Ea = 1.1-2.4 kcal/mol) rather than C-C sigma-bond insertion into the cyclopropenyl moiety (Ea = 5-24 kcal/mol). pi-Addition proceeds regioselectively through a single transition state to xylylene intermediates or directly to benzocyclobutene products.     

Regioselectivity in intramolecular addition of allylsilanes to conjugated dienones

The intramolecular addition of allylsilanes to conjugated dienones shows a divergence of regioselectivity as a function of reagent and substrate structure. The creation of 5-5, 6-5, 5-7, and 6-7 bicyclic ring systems is reported.     

Michael addition of indoles to electron deficient olefins in water catalysed by potassium bisulfate

The Michael addition of indoles to various electron deficient olefins was performed in water using potassium hydrogen sulphate as catalyst at room temperature.     

Palladium-catalyzed addition reaction of polyhaloalkanes to olefins

Pd(OAc)₂ combined with phosphines catalyzes homolytic cleavage of the C—Cl bond of CCl₄ and CCl₃CO₂CH₃ leading to facile addition to olefins under mild conditions. BrCCl₃ also reacts with olefins to give 1,1,1-trichloro-3-bromoalkanes. The reaction is accelerated under CO atmosphere, and the presence of bases such as NaOAc or K₂CO₃ is essential to attain high yields of the adducts.     

Rongalite-initiated addition of perfluoroalkyl iodides to olefins

Perfluoroalkyl iodides reacted with olefins in aqueous acetonitrile in the presence of Rongalite-sodium bicarbonate under mild conditions to give the corresponding 1:1 adducts in moderate to high yields. The formation of these products and the orientation of the addition seemed to show that radicals took part in the reaction. This provides a convenient method for perfluoroalkylation.     

Electrocatalytic addition of thiols to activated olefins

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 260–261, January, 1991.     

The electrophilic addition of selenenyl thiocyanates to olefins

Benzeneselenenyl thiocyanate in methanol reacts with olefins to give adducts; kinetic data for attack upon styrenes are presented.     

Photoinduced addition and addition–elimination reactions of perfluoroalkyl iodides to electron-deficient olefins

Photoinduced radical perfluoroalkylation of various simple electron-deficient olefins was achieved in the presence of an aqueous Na₂S₂O₃ solution. The reactions proceeded smoothly to give addition or addition–elimination products. The ability of the products to be used as radical precursors or Michael acceptors was also demonstrated.     

Rare-earth-catalyzed C-H bond addition of pyridines to olefins

An efficient and general protocol for the ortho-alkylation of pyridines via C-H addition to olefins has been developed, using cationic half-sandwich rare-earth catalysts, which provides an atom-economical method for the synthesis of alkylated pyridine derivatives. A wide range of pyridine and olefin substrates including α-olefins, styrenes, and conjugated dienes are compatible with the catalysts.     

Molecular mechanism of hydrogen bromide addition to olefins

Experimental results on the products and the kinetics of the hydrogen bromide addition to alkenes-1 in non-polar solvents and on complex formation in hydrogen bromide-olefin-solvent systems are reviewed. Theoretical calculations concerning hydrogen bromide-olefin complexes are used along with the experimental evidence to suggest a molecular mechanism of addition involving intermediate cyclic structures.     

Kinetics and mechanism of ozone addition to olefins and dienes

The mechanism of the initial stage of the ozonolysis of a series of olefins and trans-1,3-butadoiene has been investigated by the B3LYP density functional theory (DFT) method, B2PLYP double hybrid method based on DFT and the MP2 approximation, and CCSD coupled cluster method. Two possible butadiene and olefin ozonolysis mechanisms are considered: concerted 1,3-cycloaddition, which yields a primary ozonide (Criegee mechanism) and stepwise ozone addition via a biradical transition state (DeMore mechanism). The geometries of the initial and transition states and the energies of the elementary steps of the reaction have been determined. The geometric structures of the stationary states determining the rate constant of the reaction have been completely optimized using the above methods and the aug-cc-pVDZ basis set. The rate constants for both reaction pathways have been calculated. For butadiene, the contribution from nonconcerted addition can reaches 25%. According to the MRMP2 method, the overall rate constant (which includes both reaction pathways) is 1778 L mol^–1 s^–1; according to B2PLYP, 1640 L mol^–1 s^–1; according to CCSD, 1424 L mol^–1 s^–1 (aug-cc-pVDZ basis set). These results are in good agreement with experimental data (k = 3 × 10³ L mol^–1 s^–1 and with earlier calculations. The data calculated for olefins are also in agreement with experimental data.     

Regioselectivity in the palladium-catalyzed addition of carbon nucleophiles to carbocyclic derivatives.

The regioselectivity of Pd-catalyzed malonate additions and arylations to cycloalkenyl esters can be predicted by completing a stereochemical analysis of the Pd-pi-allyl complex. The Pd-catalyzed malonate additions which have the greatest degree of regioselectivity are in which substituents have a steric influence in blocking the incoming nucleophile. Cyclopentenyl substrates displayed lower regioselectivity than the cyclohexyl counterparts presumably due to increased planarity of the system. Arylations using tin and hypervalent silicon reagents were compared.     

Acyclic diastereoselection in prochiral radical addition to prochiral olefins

The stereochemical preference (syn or anti) when prochiral radicals add to prochiral acceptors is of fundamental interest. The primary focus of this research was to determine which factors influence the relative stereochemistry between the beta and gamma chiral centers when these are formed concurrently. While moderate diastereoselectivity was found for addition of alkyl (6a-d) and alpha-alkoxy radicals (16a-c) (< or =6:1 syn) to acceptors 4, 7, 8, 10, and 14, consistently high selectivity was observed with less reactive halogenated radicals (6f,g) (>15:1 anti). Steric influence in alkyl radical additions was difficult to evaluate due to decreased reactivity when using bulky reaction partners; however, more reactive alpha-alkoxy radicals, it was found that increasing steric bulk leads to moderate increases in selectivity. In addition, higher selectivity was observed when employing lanthanide Lewis acids whose environment (reactivity) was modified using achiral additives, suggesting a potentially simple means for selectivity enhancements in radical reactions. Overall these results indicate that significant stereoelectronic effects are necessary to achieve high levels of selectivity in prochiral radical additions to prochiral acceptors.     

Sulfoximidoyl radical. Homolytic addition of n-halosulfoximides to olefins

Homolytic addition reaction of N-halosulfoximides, i.e., diphenyl-N-chloro sulfoximide($\text{1}$), diphenyl-bromosulfoximide($\text{2}$), and methylphenyl-N-chloro-sulfoximide($\text{3}$), to such olefins as tert-butylethylene and cyclohexene was found to afford the corresponding N-alkylated sulfoximides, which are presumed to be formed via the initial addition of the sulfoximidoyl radical.     

Dodecacarbonyltriruthenium catalyzed one-to-one addition of N-substituted formamide to olefins

Dodecacarbonyltriruthenium (Ru₃(CO)₁₂) showed high catalytic activity for the first one-to-one addition of N-substituted formamides to both terminal and internal olefins at 180-200°C under a carbon monoxide pressure of 20 kg cm⁻². The addition of N-metylformamide to cyclopentene afforded N-methylcyclopentanecarboxamide in 90% yield.     

Molecular thermodynamics: Allowance for momentum and structural equilibrium

The possibility and the value of updating the theoretical base of classical thermodynamics were demonstrated. The energy of particles is divided between kinetic and potential energy. Universal coordinates are introduced to take account of the motion and the interaction of particles (with each other or with an external field). The theoretical potential and the application range of the formulated thermodynamics (called molecular thermodynamics) are substantially extended. The new criteria of structural and momentum equilibrium and their repercussions are introduced and illustrated, and statistical analogs are established. The mutual convexity and other unexpected characteristics of the thermodynamic functions are exposed. The applications of the theory are extended to classical and nonequilibrium systems.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 6, pp. 339–350, November–December, 1995.