64693-46-5Relevant academic research and scientific papers
Vilsmeier formylation of tert-anilines: Dibenzo[b,f][1,5]diazocines and quinazolinium salts via the 't-amino effect'
Cheng, Ying,Meth-Cohn, Otto,Taylor, David
, p. 1257 - 1262 (1998)
The attempted Vilsmeier ortho-formylation of p-substituted N,N-dimethylanilines 1 with N-formyl-N-alkylarylamides 2 unexpectedly gives dibenzo[b,f][1,5]diazocines 5 in 26-74% yield. This reaction proceeds by Vilsmeier formylation ortho to the dimethylamino group of 1 followed by hydride migration from the N-methyl group to the newly formed iminium =CH group, followed by intramolecular cyclisation, a new example of the 't-amino effect'. Similar formylation of cyclic tert-anilines such as 4-tolyl-pyrrolidines 6a,e,g, -piperidines 6b,f,h, -perhydroazepines 6c,i and -morpholine 6d, however, shows a different chemistry giving diformylated enamines 7 as the major products (12-60%). A small amount of diazocines 8 (1-13%) with a substituted benzyl at the nitrogen and N-formylated diazocines 9 are also isolated in some cases. When N-formyl-1,2,3,4-tetrahydroquinoline is used as the Vilsmeier reagent, normal formylation is observed, while use of aliphatic Vilsmeier reagents such as DMF and W-formylmorpholine give quinazolinium salts 16 and 17, also by way of the 't-amino effect'. The key feature in these formylations is the hydride transfer from the α-position of a tertiary amine to an unsaturated ortho-substituent CH=NR2+, the 't-amino effect'.
Vilsmeier Formylation of para-Substituted tert-Anilines Results in Dibenzodiazocines or Quinazolinium salts: a Remarkable Example of the 't-Amino Effect'
Meth-Cohn, Otto,Taylor, David L.
, p. 1463 - 1464 (1995)
Formylation of para-substituted tert-anilines with various N-formylated sec-anilines in phosphoryl chloride results in ortho-formylation followed by cyclisation of the iminium salt to the adjacent tert-amino α-position by way of the 't-amino effect' giving dibenzodiazocines; in a similar manner, with N-formylated sec-aliphatic amines, quinazolinium salts are formed while bulky formanilides give the expected ortho-formylated tert-aniline.
Interaction of barbituric acids with o-dialkylaminobenzaldehydes
Krasnov, Konstantin A.,Kartsev, Viktor G.,Khrustalev, Victor N.
, p. 52 - 54 (2007/10/03)
Barbituric or 2-thiobarbituric acids interact with o- dialkylaminobenzaldehydes to give 5-o-dialkylaminobenzylidene derivatives, which cyclise into 2,4,6-trioxoperhydropyrimidine-5-spiro-3′-(1′, 2′,3′,4′-tetrahydroquinolines) under mild conditions; the me
Synthesis of 2-substituted benzofurans and indoles using functionalized titanium benzylidene reagents on solid phase
Macleod, Calum,McKiernan, Gordon J.,Guthrie, Emma J.,Farrugia, Louis J.,Hamprecht, Dieter W.,Macritchie, Jackie,Hartley, Richard C.
, p. 387 - 401 (2007/10/03)
Titanium(IV) benzylidenes bearing a masked oxygen or nitrogen nucleophile in the ortho position were generated from thioacetals, using low-valent titanocene complex, Cp2Ti[P(OEt)3]2. Methylene acetal, alkyl ether, silyl ether, fluoro, tertiary amino, and N-alkyl, N-benzyl, N-prenyl, and N-silyl tert-butyl carbamate groups were tolerated in the titanium alkylidene reagents (Schrock carbenes). Aryl-chlorine bonds were stable to the titanium benzylidene functionality, but there was poor chemoselectivity for the reduction of the thioacetal in the presence of an aryl chloride. The titanium benzylidenes converted Merrifield and Wang resin-bound esters into enol ethers. The oxygen nucleophile was masked as a TMS ether, and when the resin-bound enol ethers bearing this ortho substituent were treated with 1% TFA in dichloromethane, benzofurans were released from resin in high yields. The chameleon catch strategy ensured excellent purity. In a similar way, N-alkylated and N-silylated tert-butyl carbamates were used for the synthesis of N-alkyl and N-Boc indoles, respectively. These traceless solid-phase syntheses of heterocycles are believed to involve post-cleavage modification rather than cyclative termination.
