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The pyrroloindole ring system characterized of the physostigmine alkaloids is formed in the interrupted indolization between an arylhydrazine and N-protected 2-hydroxy-3-methylpyrrolidine, and it is accomplished in hot HOAc.1
With ligand 1 hydroformylation of 2-alkenes catalyzed by (acac)Rh(CO)2 proceeds via a double bond shift.1 In the presence of an amine the reaction becomes a hydroamination process (amino group introduced at the carbon chain terminus).2
Ligand 2 is for linear hydroformylation of 1-alkenes, in which the amidate groups bring the catalyst into the aqueous phase as the bicarbonate salt is formed.3 Developed for highly linear hydroformylation of 1-alkenes, including allyl cyanides, is a ligand series represented by 3.4
When ligands such as 4 for the Rh catalyst are used the aldehyde products undergo reduction to yield primary alcohols.5 Simpler ligands such as (4-FC6H4)3P can be used in the hydroacylation of enamides to form 1,4-dicarbonyl compounds.6
Homoallylic alcohols form 5-membered cyclic products even if the new CC bond formation is with the internal sp2-carbon atom.7 Double trapping of the homologous aldehyde derived from 4-bromo-1-butene with 2-phenyl-2-aminoethanol leads to a bicyclic heterocycle which is amenable to substitution at the a-carbon to the nitrogen atom.8
Under normal hydroformylation condition but with addition of a secondary amine and 2,2´,6,6´-tetrakis(diphenylphosphinomethyl)biphenyl to the reaction mixture, Schiff bases are formed and then reduced.9
The removal of CO from 2-(2-acylaryl)pyridines by heating with (acac)Rh(CO)2 is of synthetic interests because the ketone substrates are generally more readily accessible.10
Cross-conjugated ketones in which one of the double bonds belongs to a benzofuran nucleus undergo Nazarov cyclization.1 Enolacetylation to create a highly electrophilic moiety for the reaction to proceed is most likely.
These reagents are excellent acyl donors to OH-compounds.1
A review of the acylating capability of 1-acylpyrazoles has been published.1
Alkoxyboranes 1 are useful catalysts for cleavage of 1,3-dicarbonyl compounds such as ß-keto esters and N-acylamides by alcohols under essentially neutral conditions. These boranes perform activation on both reactants.1
Cleavage of the small ring of 3-arylcyclobutanones that is o-substituted by a heteroatom group such as disilane is attended by heterocyclization.
Benzyl cyanoacetates extrude CO2 while the remaining parts recombine to afford 3-arylpropanenitriles. In the case of 2-furylmethyl cyanoacetates the choice of the phosphine ligand affects the recombination step. It can be coaxed toward formation of 2-cyanomethyl-5-methylfurans.2
In the presence of (?3-C3H5)Pd(S4Mo3) the allylation of arylamines can use allyl alcohol. The allyl group is to be attached to C-3 of an indole nucleus.
On treatment with AlCl3, the protecting group of N-mesylindoles migrates to C-7.1
Condensation of ArCHO, MeCN and MeCOAr' to afford ArCH(NHAc)CH2COAr' is observed on treatment with AlCl3 and AcCl. ß-Keto esters undergo a similar reaction.
?,d-Unsaturated ketones cyclize to form a benzene ring in the presence of AlCl3 in dioxane.3
Ethers are split by silyldealkylation of ethers using R3SiCl, with AlCl3 or FeCl3 or BiCl3 as promoter. The other products are RCl.
High-surface AlF3 is able to activate aliphatic C-H bond under very mild conditions (at 40o), and this property can be exploited by deuteration.1
Benzyl and cinnamyl alcohols are easily converted into the corresponding amines with the aid of Al(OTf)3.1 Substitution using other nucleophiles are equally smooth, as exemplified in the construction of an intermediate for a synthesis of mersicarpine.2
The reaction of tri-O-benzylglucal with an alcohol on catalysis by Al(OTf)3 temperature can change the reaction mechanism.3 At 0o Ferrier rearrangement products are formed but at 60o addition to the double bond is favored.
The title reagent is a more bulky analog of ATPH and perhaps more sensitive to steric effects. Its application as catalyst in site-selective condensation such as reaction between crotonic esters and aldehydes to form 5-hydroxy-2-alkenoates has been demonstrated.
The commercially available mesionic "Nitron" has an N-heterocyclic carbene (NHC) tautomer, but its application in directing reactions has yet to be explored.1 Electron properties and stability of imidazole-based mesionic carbenes (imidazol-5-ylidenes) are found to be inversely correlated.2
Imidazolium and imidazolinium bicarbonate salts are air-stable precursors of NHC's.3 1,3-Bis(2,6-dimethoxyphenyl)imidazol-2-ylidene is a typical electron-rich carbene.4 A photoswitchable NHC pair is 2A and 2B, interconverted by uv and visible...
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