Search results for "Proton"
showing 10 items of 5886 documents
Syntheses with organoboranes. Part 14: Enolization–aldolization of conjugated cyclohexenones via dienolborinates
2002
Abstract Enolization of cyclohex-2-enone ( 1 ), 3-methyl- ( 2 ), 3,5-dimethyl- ( 3 ), 3,5,5-trimethyl- ( 4 ), and 3,4,5,5-tetramethylcyclohex-2-enone ( 5 ) with chlorodicyclohexylborane proceeds by deprotonation at the 6-position. Aldolization of the dienolborinates with benzaldehyde, and acetaldehyde, provides the corresponding anti aldols with 87–95% selectivity. Ketones 4 and 5 undergo competitive deprotonation at the 3-methyl group and aldolization at the 2-position. In contrast, lithium dienolates derived from 4 and 5 gave syn aldols with 95% selectivity.
Mono-, bi- and polynuclear complexes of dimethyldiphenylsilane, diphenylether and biphenyl with Cr, Co and Ru. Synthesis and 1H, 13C, 17O and 29Si NM…
1995
Abstract Mono- and bimetallic transition metal carbonyls of dimethyldiphenylsilane, Ph 2 Si(CH 3 ) 2 (L1), diphenylether, Ph 2 O (L2) and biphenyl, Ph 2 (L3): Ph 2 Si(CH 3 ) 2 Cr(CO) 3 ( 1 ), Ph 2 Si(CH 3 ) 2 [Cr(CO) 3 ] 2 ( 2 ), Ph 2 Si(CH 3 ) 2 Co 4 (CO) 9 ( 3 ), Ph 2 Si(CH 3 ) 2 [Co 4 (CO) 9 ] 2 ( 4 ), Ph 2 Si(CH 3 ) 2 Cr(CO) 3 Co 4 (CO) 9 ( 5 ), Ph 2 OCr(CO) 3 ( 6 ), Ph 2 OCo 4 (CO) 9 ( 7 ), Ph 2 ORu 6 C(CO) 14 ( 8 ), Ph 2 OCr(CO) 3 Co 4 (CO) 9 ( 9 ) and Ph 2 Ru 6 C(CO) 14 ( 10 ) have been prepared and characterized by means of 1 H, 13 C, 17 O and 29 Si NMR spectroscopy. The same order of the shielding effects induced by the transition metal (Co 1 H NMR chemical shifts of the η 6 -coord…
Metalloporphyrins with metalmetal σ-bonds. Synthesis, spectroscopic characterization, and electrochemistry of (P)MRe(CO)5 where P is the dianion of …
1991
Abstract The synthesis, physicochemical properties, and electrochemistry of a new series of metal metal σ-bonded metalloporphyrins are reported. The investigated compounds are represented as (P)MRe(CO)5 where P is the dianion of octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP) and M = Al, Ga, In, or Tl. These compounds provide the first examples of Al and Ga metalloporphyrins with covalent metalmetal bonds as well as give the first series of compounds in which the same metalate anion is covalently bonded to four different group 13 metalloporphyrins. Each synthesized complex was characterized by 1H NMR, IR, and UV-visible spectroscopy as well as by electrochemistry. Graham Δσ and Δπ …
Synthesis of an enantiopure 2-arylcyclohexanols from prochiral enol acetates by an enantioselective protonation/diastereoselective reduction sequence
2003
Abstract The enantioselective protonation with 2-sulfinyl alcohols of lithium enolates of 2-arylcyclohexanones with different substituents on the phenyl group takes place with excellent enantioselectivities (89–99%). Chiral 2-phenylcyclohexanone and 2-arylcyclohexanones carrying electron donor substituents on the aromatic ring are converted into the corresponding trans -2-arylcyclohexanols by diastereoselective reduction with sodium naphthalenide in the presence of acetamide. The stereochemical integrity of the tertiary stereocenter is fully preserved using this reduction procedure. Interestingly, the chiral proton source is not consumed in the synthesis.
PREPARATION AND REACTIONS OF 2-PYRIDYLPLATINUM(II) COMPLEXES [PTCL(C5H4N-C2)(TERTIARY PHOSPHINE)2] - COMPOUNDS WITH A MARKEDLY NUCLEOPHILIC PYRIDINE …
1989
Abstract The 2-pyridyl complex trans -[PtCl(C 5 H 4 N- C 2 )(PPh 3 ) 2 ] (I) can be prepared in high yield by oxidative addition of 2-chloropyridine to [Pt(PPh 3 ) 4 ]. The reaction of I with 1,2-bis(diphenylphosphino)ethane yields the cis derivative [PtCl(C 4 5 H 4 N- C 2 )(dppe)] (II). In polar solvents, the latter rearranges to the binuclear cationic complex [Pt(μ-C 5 H 4 N- C 2 , N )(dppe)] 2 Cl 2 . The reaction of I with [PdCl(η 3 -2-MeC 3 H 4 )] 2 (1/0.5 molar ratio) gives the products [PtCl(μ-C 5 H 4 N- C 2 , N )(PPh 3 )] 2 (IV) and [PdCl(η 3 -2-MeC 3 H 4 )(PPh 3 )]. 31 P NMR monitoring of the reaction suggests that PPh 3 transfer occurs in a binuclear platinum/palladium intermediate…
"Table 4" of "Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets …
2013
Figure 2-a. Expected limit +1sigma.
"Table 9" of "Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets …
2013
Figure 2-b. Observed limit -1sigma-th.
"Table 7" of "Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets …
2013
Figure 2-b. Observed limit +1sigma-th.
"Table 2" of "Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets …
2013
Figure 2-a. Observed limit.
"Table 10" of "Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets…
2013
Figure 2-b. Expected limit +1sigma.