2.6- Di-r-butyl-4-methylpyridine

Cp3S03Me, CH2CI2, Pyr, 80°, 2.5 h, 85-90% yield.The use of 2,6-di-r-butyl-4-methylpyridine as a base is also very effective. ... 

Cationic cyclization. A key step in the synthesis of the diterpenes cafestol5 and atractyligenin4 involves a novel cation cyclization of bicyclic cyclopropanes to the tetracyclic systems of the diterpenes (equations I and II). Thus treatment of 1 with a slight excess of triflic anhydride and 2,6-lutidine effects cyclization to the rather unstable pentacycle 2 with the kaurene system. The related conversion of 3 to 4 can be effected with triflic anhydride and 2,6-di-r-butyl-4-methylpyridine in 1-nitropropane. 

Section V contains specific examples of procedures for Inflate synthesis some general comment about these procedures is worthwhile. Triflic anhydride is the reagent of choice for preparing triflates derived from sugars, whereas triflyl chloride is used more often when uucleosides are involved. Triflate formation with triflic anhydride requires addition of a base (usually pyridine) to the reaction mixture to neutralize the triflic acid produced [Eq. (4) 7]. Some triflates are reactive enough that pyridine can function as a nucleophile in the substitution process. In these instances, replacement of pyridine with a non-nucleophilic base, such as 2,6-di-r-butyl-4-methylpyridine, avoids this undesired reaction (Scheme 1) [7]. 

The conditions using 2,4,6-collidine/Tf20 and having the reaction warm from -78 °C to 25 °C were chosen mainly to avoid using more expensive reagents such as 2,6-di-r-butyl-4-methylpyridine or A-phenyl triflimide. (a) Stang, P. J. Hanack, M. C. Subramanian, L. R. Synthesis 1982, 85. (b) McMurray, J. E. Scott, W. J. Tetrahedron Lett. 1983,24,979. 

Di-r-butyl-4-methylpyridine, 141, 485 Di-/-butylmethylsilyl perchlorate, 78 Di-n-butyltin oxide, 141... 

Methylation of carbohydrates. Carbohydrates can be methylated in >80% yield by methyl triflate and a sterically hindered, weak base such as 2,6-di-t-butylpyridine and 2,6-di-r-butyl-4-methylpyridine. The method is useful for sugars that are sensitive to acids or bases. 

In fact, the sensitive disubstituted alkene of 14 turned out to not be stable to the subsequent AlCl, coupling conditions, so the alkene and the secondary alcohol were protected together as the bromoether 15. Condensation of the derived enol ether 16 with the sulfone 2 in the presence of DTBMP (2,6-di-r-butyl-4-methylpyridine) then gave 17. Yamaguchi lactonization followed by regeneration of the alkene by zinc reduction completed the synthesis of 1. 

A synthesis of the tetrahydroquinoline enediyne structure (6) of the antibiotic dynemicin involves condensation of a Co(CO)6-protected propargylic alcohol with an enol. Thus treatment of 4 with triflic anhydride and 2,6-di-r-butyl-4-methylpyridine in CH2CI2/CH3NO2 results in 5 in 52% yield. (Use of nitromethane is crucial for satisfactory results.) This product on decomplexation with iodine provides 6, which undergoes aromatization when heated to form 7. 

Miscellaneous Metal-mediated Reactions. The gallium-catalyzed ortAo-ethynylation of phenols has been achieved with chloro- or (iodoethynyl)trimethylsilane and a variety of phenols. GaUium(ni) chloride (0.10 equiv), n-BuLi (0.30 equiv), and 2,6-di-r-butyl-4-methylpyridine (0.10 equiv) in the presence of haloalkyne and phenol in chlorobenzene at 120°C gave 81-90% yield of a variety of D-(trimethylsilylethynyl)phenols (eq 10). ... 

MID = 1-methylimidazole, DTBP = 2,6-di-r-butylpyridine, DMP dimethylpyridine, DTBMP = 2,6-di-r-butyl-4-methylpyridine. 

Alcohols can be converted to methyl ethers by the use of MeOTf + 2,6-di-f-butylpyridine or 2,6-di-r-butyl-4-methylpyridine. This procedure was initially developed in the carbohydrate field. Me3P04 provides a good polar solvent for this process. A recent application, in the synthesis directed at lonomycin, was to methylation of the complex alcohol (1) without causing retro-aldol cleaveage. ... 

Pyridine can become involved in nucleophilic substitution when very reactive triflates are being synthesized. One approach to minimize this disadvantage is to replace it with ster-ically hindered bases, such as 2,6-di-r-butyl-4-methylpyridine, 2,4,6-trisubstituted pyrimidines, or nonnucleophilic aliphatic amines (usually N,(V-diisobutyl-2,4-dimethyl-3-pentylamine). No salt formation appears to take place under these conditions. The triflic anhydride seems to be the direct triflating agent and the base only neutralizes the triflic acid formed. Numerous alkyl triflates have been prepared in the literature by the above method. Some recent examples of triflates prepared from alcohols are illustrated in eqs 2 and 3. As an exception, 2,6-dinitrobenzyl alcohol does not react with Tf20 although similar sulfonyl esters could be prepared. ... 

Other bases such as pyridine, lutidine, EtaN," polymer-bound 2,6-di-r-butyl-4-methylpyridine, - and 2,4,6-trialkyl-substituted pyrimidines were also used. The commercially available Ai,At-diisobutyl-2,4-dimethyl-3-pentylamine is a very convenient base to prepare the vinyl triflates. In the case of non-functionalized ketones, anhydrous Na2C03 has been proved to be very successful. ... 

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