175223-64-0Relevant academic research and scientific papers
The iso-VAPOL ligand: Synthesis, solid-state structure and its evaluation as a BOROX catalyst
Gupta, Anil K.,Zhang, Xin,Staples, Richard J.,Wulff, William D.
, p. 4406 - 4415 (2015/02/02)
The new vaulted biaryl ligand iso-VAPOL is an isomer of VAPOL but has the chiral pocket of VANOL. The synthesis of iso-VAPOL involves a cycloaddition/electrocyclization cascade (CAEC) similar to one that is used for VAPOL except that the starting material
An examination of VANOL, VAPOL, and VAPOL derivatives as ligands for asymmetric catalytic Diels-Alder reactions
Heller, Douglas P.,Goldberg, Daniel R.,Wu, Hongqiao,Wulff, William D.
, p. 1487 - 1503 (2007/10/03)
Several derivatives of the vaulted biaryl ligand VAPOL were prepared and evaluated as chiral ligands for aluminum Lewis acids in the catalytic asymmetric Diels-Alder reactions of methyl acrylate and methacrolein with cyclopentadiene. The substituents on VAPOL were introduced into the 6- and 6′-positions in an effort to further extend the chiral pocket of the major groove, which contains the phenol functions at the 4- and 4′-positions. The set of four new ligands that have been prepared have the following groups introduced into the 6- and 6′-positions of VAPOL: bromide, methyl, phenyl and 3,5-di-t-butylphenyl. All of these ligands give lower asymmetric inductions than the unsubstituted VAPOL for the Diels-Alder reactions of both methyl acrylate and methacrolein. The positive cooperativity of added carbonyl compounds on the autoinduction in the Diels-Alder reaction of methyl acrylate and cyclopentadiene were also investigated with the VANOL and VAPOL ligands as well as the 6,6′-dibromo and 6,6′-diphenyl derivatives of VAPOL. Only the reaction with VAPOL showed any significant positive cooperativity. The reaction with VANOL was sluggish at -78°C, but at higher temperatures, the reaction did exhibit positive cooperativity that was similar to that of VAPOL. Finally, no positive cooperativity was observed with the VAPOL ligand for the reaction of methacrolein and cyclopentadiene.
New synthesis of vaulted biaryl ligands via the Snieckus phenol synthesis
Yu, Su,Rabalakos, Constantinos,Mitchell, William D.,Wulff, William D.
, p. 367 - 369 (2007/10/03)
(Chemical Equation Presented) In an effort to develop a synthesis of the VAPOL ligand that avoids the use of a chromium carbene complex, a route was examined that involved the annulation of a naphthalene carboxamide via the method of Snieckus. The latter
Synthesis, resolution, and determination of absolute configuration of a vaulted 2,2′-binaphthol and a vaulted 3,3′-biphenanthrol (VAPOL)
Bao, Jianming,Wulff, William D.,Dominy, James B.,Fumo, Michael J.,Grant, Eugene B.,Rob, Alexander C.,Whitcomb, Mark C.,Yeung, Siu-Man,Ostrander, Robert L.,Rheingold, Arnold L.
, p. 3392 - 3405 (2007/10/03)
Two methods for the synthesis of vaulted biaryls were developed involving the reactions of carbene complexes with alkynes and the [2 + 2] cycloaddition of ketenes. The final step in the synthesis of 3,3′-diphenyl-[2,2′-binaphthalene]-1,1′-diol (39) and 2,2′-diphenyl-[3,3′-biphenanthrene]-4,4′-diol (47) (VAPOL) was phenol coupling of the 3-phenyl-1-naphthol (14) and the 2-phenyl-4-phenanthrol (28), respectively. The naphthol 14 could be prepared from the thermolysis of phenylacetyl chloride in the presence of phenylacetylene or from the benzannulation of the pentacarbonyl(phenylmethoxymethylene)chromium(0) (15) with phenylacetylene which upon an acetylative workup gives O-acetyl-4-methoxy-2-phenyl-1-naphthol (16). The reductive cleavage of the acetoxy group in 16 was unexpectedly affected by aluminum chloride and ethanethiol which were used to cleave the methyl ether. In a similar manner, the phenanthrol 28 could either be prepared from the 1-naphthylacetyl chloride (30) or pentacarbonyl-(1-naphthylmethoxymethylene)chromium(0) (21). A new procedure for the preparation of carbene complexes was developed utilizing dimethyl sulfate as methylating agent. Unlike the benzannulation of the phenyl complex 15, the benzannulation of the naphthylcarbene complex 21 with phenylacetylene gave a side product which resulted from the incorporation of 2 equiv of the alkyne. This side product could be minimized by the proper control of the concentration of the alkyne. The phenol coupling of the 3-phenyl-1-naphthol with ferric chloride gave 2,2′-diphenyl-[2,2′-binaphthalene]-4,4′-diol (38) and with air as oxidant gave the of 3,3′-diphenyl-[2,2′-binaphthalene]-1,1′-diol (39). Oxidative coupling of the 2-phenyl-4-phenanthrol (28) with air gave 2,2′-diphenyl-[3,3′-biphenanthrene]-4,4′-diol (47) (VAPOL), but the same coupling with 2-tert-butyl-4-phenanthrol (34) failed. The 2,2′-binaphthol 39 was resolved via its cyclic diester with phosphoric acid by salt formation with (-)-brucine, and the 3,3′-biphenanthrol 47 was resolved via its cyclic deiester with phosphoric acid (49) by salt formation with (-)-cinchonidine. The configuration of (-)-39 was shown to be S from an X-ray analysis of the brucine salt, and the configuration of (+)-47 was shown to be S from an X-ray analysis the amide (S,S)-54 derived from 49 and (S)-α-methylbenzylamine.
