Sequential Allenylidene/Vinylidene Cyclization for Stereoselective Construction of Bicyclic Carbocycles from Propargyl Alcohol

Consecutive cyclization reactions of phenyl propargyl alcohols 1 and 2 are catalyzed by [Ru]NCCH3+ ([Ru] = Cp(PPh3)2Ru) in cosolvent CHCl3/MeOH at 60 °C, to afford the fused cyclic compounds 11a (R = Me) and 10a (R = Me), respectively

Sequential Allenylidene/Vinylidene Cyclization for Stereoselective Construction of Bicyclic Carbocycles from Propargyl Alcohol

Consecutive cyclization reactions of phenyl propargyl alcohols <b>1</b> and <b>2</b> are catalyzed by [Ru]NCCH₃⁺ ([Ru] = Cp(PPh₃)₂Ru) in cosolvent CHCl₃/MeOH at 60 °C, to afford the fused cyclic compounds <b>11a</b> (R = Me) and <b>10a</b> (R = Me), respectively

Carbon−Carbon Bond Formation between Furyl and Triphenylphosphine Ligands in Ruthenium Complexes

The η3-allylic complex 8 was obtained from thermolysis of the neutral ruthenium furyl complex 7 with an unsaturated carbon chain on the furyl ligand. Protonation of complex 8c with HBF4 generates complex 9c with an oxygen atom and an olefin group coordinated to the ruthenium metal

Carbon−Carbon Bond Formation between Furyl and Triphenylphosphine Ligands in Ruthenium Complexes

The η3-allylic complex 8 was obtained from thermolysis of the neutral ruthenium furyl complex 7 with an unsaturated carbon chain on the furyl ligand. Protonation of complex 8c with HBF4 generates complex 9c with an oxygen atom and an olefin group coordinated to the ruthenium metal

Syntheses, Reactivity, and Stereochemistry of η³-Allyl Dithio-Molybdenum Complexes: Crystal Structures of <i>e</i><i>ndo</i>-[Mo(η³-C₃H₅)(η²-S₂CNC₄H₈)(CO)(η²-dppe)], <i>e</i><i>ndo</i>-[Mo(η³-C₃H₅){η²-S₂P(OEt)₂}(CO)(η²-dppe)]<i>, </i><i>e</i><i>xo</i>-, <i>e</i><i>ndo</i>-[Mo(η³-C₃H₅)(η²-S₂CNC₄H₈)(CO)(η²-dppm)], and <i>e</i><i>ndo</i>-[Mo(η³-C₃H₅){η²-S₂P(OEt)₂}(CO)(η²-dppm)]

The reactions of η3-allyldicarbonyldithiomolybdenum(II) compounds [Mo(η3-C3H5)(CO)2(η2-L2)(X)] (L2, X = S2CNC4H8 (1a); S2CNEt2 (1b); S2P(OEt)2, CH3CN (1c)) with diphos in refluxing acetonitrile give a mixture of endo and exo complexes [Mo(η3-C3H5)(η2-L2)(CO)( η2-diphos)] (diphos:  dppe = {1,2-bis(diphenylphosphino)ethane} (2−4); dppm = {bis(diphenylphosphino)methane} (5−7); dppa = {bis(diphenylphosphino)amine} (8−10)). The orientations of endo and exo are defined for the open face of the allyl group and carbonyl group in the same direction in the former and opposite directions in the latter. In solution, both the endo and the exo isomers are present in dithiocarbamate Mo complexes, whereas only the endo conformer is present in dithiophosphate dppe and dppa Mo complexes. The variable-temperature 1H and 31P{1H} NMR experiments and X-ray crystal structures of endo-[Mo(η3-C3H5)(η2-S2CNC4H8)(CO)(η2-dppe)] (2), endo-[Mo(η3-C3H5){η2-S2P(OEt)2}(CO)(η2-dppe)] (4), exo- and endo-[Mo(η3-C3H5)(η2-S2CNC4H8)(CO)(η2-dppm)] (5), and endo-[Mo(η3-C3H5){η2-S2P(OEt)2}(CO)(η2-dppm)] (7) are used to elucidate the allyl rotation mechanism and the two orientations. The activation barriers of interconversion were determined to be 61.5 ± 0.4 (3) and 65.1 ± 0.4 kJ mol-1 (5). X-ray analysis on 5 shows that the unit cell contains two independent molecules, endo and exo, which differ mainly by the orientation of the allyl group with respect to the carbonyl group. This is the first example of such a conformation in the crystal structure of the Mo(η3-C3H5)(η2-L) derivative

Synthesis of Dinuclear and Trinuclear Ruthenium Cyclopropenyl Complexes

Dinuclear ruthenium cyclopropenyl complexes ([Ru] = (η5-C5H5)(PPh3)2Ru, R = CN, 3a; R = CH2CH2, 3b; R = Ph, 3c) are prepared by deprotonation of corresponding vinylidene complexes {[Ru]CC(CH2R)}2C6H42+ (2). For the vinylidene complex 2d (R = CO2Me) with an ester group, the deprotonation reaction leads to formation of the dinuclear bis-furyl complex (5d). Electrophilic addition of TCNQ to both three-membered rings of 3a yields the zwitterionic bis-vinylidene complex {[Ru]CC[CH(TCNQ)CN]}2C6H4 (4a), which, in the presence of MeOH/n-Bu4NOH, gives the methoxy-substituted bis-cyclopropenyl complex (6a). The proton-induced demethoxylation of 6a generates (7a). The reaction of TMSN3 with 3a gives the bis-tetrazolate complex {[Ru](N4C)CH(CH2CN)}2C6H4 (8a). Trinuclear tris-cyclopropenyl complexes (R = CN, 11a; R = CH2CH2, 11b; R = Ph, 11c) are obtained from deprotonation of {1,3,5-{[Ru]CC(CH2R)C6H4C⋮C}3C6H3}3+ (10). Complex 2b is characterized by X-ray diffraction analysis, and other complexes are characterized by spectroscopic methods

Chemistry of Ruthenium Azirinyl Complexes and Reversed Regiospecificity of the Carbonyl Insertion Reaction

The three azirinyl complexes (R = CN, CHCH2, Ph) are obtained from deprotonation of isonitrile complexes. For R = Ph, three isomers including 1H- and 2H-azirinyl complexes are observed at low temperature. Insertion of CO groups of acetone, aldehyde, ester, and amide into the azirinyl ligand follows regiospecificity opposite that in the photochemical-induced insertion of the organic azirine system

Reactions of Ruthenium Acetylide and Vinylidene Complexes Containing a 2-Pyridyl Group

Two ruthenium acetylide complexes [Ru]CC(C5H3RN) (1a, R = H; 1b, R = Me; [Ru] = Cp(PPh3)2Ru) containing 2-pyridyl groups are prepared and their chemical reactivities are explored. Protonation of the ruthenium acetylide complex 1a with HBF4 takes place at both the nitrogen atom and Cβ, giving the dicationic pyridiniumvinylidene complex {[Ru]CC(H)(C5H4NH)}(BF4)2 (3a). Addition of BF3 to 1a yields the Lewis acid/base adduct [Ru]CC(C5H4N→BF3) (4a). In the presence of moisture both complexes 3a and 4a in solution transform into the cationic heterocyclic carbene complex {[Ru]C(O)CH2(C5H4N→BF2)}BF4 (6a), for which the structure is confirmed by X-ray structure determination. The formation of 6a involves the intermediate {[Ru]CC(H)(C5H4N→BF2OH)}BF4 (5a), characterized by spectroscopic methods. DFT calculations show that the Gibbs free energy change of the exothermic transformation of 5a to 6a is −20.59 kcal/mol. N-Alkylation reactions of 1b with two alkyl bromides BrCH2R′ (R′ = CHCHCO2Me and CO2Me) yield two pyridiniumacetylide complexes {[Ru]CC(C5H3MeNCH2R′)}Br (7b, R′ = CHCHCO2Me; 7c, R′ = CO2Me, respectively). Complex 7c, characterized by X-ray structure determination, undergoes further protonation to give the pyridiniumvinylidene complex {[Ru]CC(H)(C5H4NCH2R′)2+ (8c). Interestingly, the acetylide complex 7b undergoes a C−C coupling reaction of the acetylic Cβ with the CC double bond to give the vinylidene complex 9b, characterized also by X-ray structure determination

Reactions of Ruthenium Acetylide and Vinylidene Complexes Containing a 2-Pyridyl Group

Two ruthenium acetylide complexes [Ru]CC(C5H3RN) (1a, R = H; 1b, R = Me; [Ru] = Cp(PPh3)2Ru) containing 2-pyridyl groups are prepared and their chemical reactivities are explored. Protonation of the ruthenium acetylide complex 1a with HBF4 takes place at both the nitrogen atom and Cβ, giving the dicationic pyridiniumvinylidene complex {[Ru]CC(H)(C5H4NH)}(BF4)2 (3a). Addition of BF3 to 1a yields the Lewis acid/base adduct [Ru]CC(C5H4N→BF3) (4a). In the presence of moisture both complexes 3a and 4a in solution transform into the cationic heterocyclic carbene complex {[Ru]C(O)CH2(C5H4N→BF2)}BF4 (6a), for which the structure is confirmed by X-ray structure determination. The formation of 6a involves the intermediate {[Ru]CC(H)(C5H4N→BF2OH)}BF4 (5a), characterized by spectroscopic methods. DFT calculations show that the Gibbs free energy change of the exothermic transformation of 5a to 6a is −20.59 kcal/mol. N-Alkylation reactions of 1b with two alkyl bromides BrCH2R′ (R′ = CHCHCO2Me and CO2Me) yield two pyridiniumacetylide complexes {[Ru]CC(C5H3MeNCH2R′)}Br (7b, R′ = CHCHCO2Me; 7c, R′ = CO2Me, respectively). Complex 7c, characterized by X-ray structure determination, undergoes further protonation to give the pyridiniumvinylidene complex {[Ru]CC(H)(C5H4NCH2R′)2+ (8c). Interestingly, the acetylide complex 7b undergoes a C−C coupling reaction of the acetylic Cβ with the CC double bond to give the vinylidene complex 9b, characterized also by X-ray structure determination

Reactions of Ruthenium Acetylide Complexes with Isothiocyanate

Treatment of Cp(PPh3)[P(OMe)3]RuC⋮CPh (2; Cp = η5-C5H5) with PhNCS at room temperature affords the [2 + 2] cycloaddition (3a), containing a four-membered ring, and the neutral vinylidene phosphonate complex Cp(PPh3)[P(O)(OMe)2]RuCC(Ph)C(SH)NPh (4a) in a 9:1 ratio. Formation of 4a results from an Arbuzov-like dealkylation reaction possibly after addition of PhNCS. The same reaction at 40 °C affords a higher yield of 4a (5a; R = Ph) which results from addition of a second isothiocyanate to the four-membered ring of 3a. The reaction of 2 with PhCH2NCS at room temperature directly affords the six-membered-ring product 5b (R = CH2Ph). Trimerization of phenyl isothiocyanate is catalyzed by Cp(dppe)RuC⋮CPh (1‘; dppe = Ph2PCH2CH2PPh2) in refluxing CH2Cl2. This catalytic reaction proceeds through a pathway in which the first two steps are the same as those observed in the reaction of 2a. An attempt to purify the precursor of the trimerization product gave the cocrystallization of 1‘ and (PhNCS)3 (8). The structures of 3a, 4a, 5b, and the cocrystallization product of 1‘ and 8 have been determined by single-crystal X-ray diffraction analysis