Silver(I)-Catalyzed Aminocyclization of 2,3-Butadienyl and 3,4-Pentadienyl Carbamates: An Efficient and Stereoselective Synthesis of 4-Vinyl-2-oxazolidinones and 4-Vinyltetrahydro-2H-1,3-oxazin-2-ones
Silver(I) salts catalyze an aminocyclization of O-(2,3-butadienyl) N-tosyl-carbamates to provide mixtures of cis and trans-5-substituted N-tosyl-4-vinyl-2-oxazolidinones, the trans-isomers predominantly or exclusively.
Palladium-Catalyzed Stereoselective Allylaminocyclization and 1,3-Butadien-2-ylaminocyclization of Allenyl Tosylcarbamates
作者:Masanari Kimura、Shuji Tanaka、Yoshinao Tamaru
DOI:10.1021/jo00117a031
日期:1995.6
Palladium [PdCl2(PhCN)(2) or Pd-2(dba)(3) . CHCl3 (dba = dibenzylideneacetone)], in the presence of a base (Et(3)N or K2CO3) in THF at room temperature, catalyzes an allylaminocyclization of 2,3-butadienyl tosylcarbamates 1 with allylic chlorides to selectively provide trans-4,5-disubstituted 2-oxazolidinones 2 in good yields. Under similar conditions, Pd(PPh(3))(4) catalyzes an N-allylation of 1 to give 3. A limited number of 3,4-pentadienyl tosylcarbamates 5 undergo the allylaminocyclization to provide tetrahydro-1,3-oxazin-2-ones 6. In the absence of an allylic chloride, Pd(PPh(3))(4) and PdCl2(PhCN)(2) catalyze a formal dimerization of 1 to provide C-4-triene-substituted 2-oxazolidinones 4 in moderate to good yields.
Iodocyclization of the (tolylsulfonyl)- and (trichloroacetyl)carbamates of secondary .alpha.-allenic alcohols. Highly diastereoselective synthesis of syn-1,2-amino alcohols and trans-5-alkyl-1-oxo-2-oxazolidine-4-carboxylic acids
作者:Richard W. Friesen、Aleksandra E. Kolaczewska
DOI:10.1021/jo00016a016
日期:1991.8
The iodocyclization of tosyl- and (trichloroacetyl)carbamates 9 and 10, respectively, of secondary alpha-allenic alcohols is described. The cyclofunctionalization reactions are highly diastereoselective, providing trans-5-alkyl-4-(1-iodoethylene)-2-oxazolidinones 11 and 12 as the major diastereomers in ratios of 6.3:1 to > 99: < 1. The mechanism of cyclization involves the initial formation of diiodides resulting from the addition of I2 to the terminal olefin of the allene moiety, followed by a kinetically controlled intramolecular SN2' displacement of iodide. Hydrolysis and acetylation of the N-tosyloxazolidinones 11 provide syn-1,2-amino alcohol derivatives 15. Alternatively, ozonolysis of the vinyl iodides derived from the cyclization of the (trichloroacetyl)carbamates 12 provides a novel, efficient, and highly diastereoselective route to trans-5-alkyl-2-oxazolidinone-4-carboxylic acids 25 and esters 26.
A highly stereoselective conversion of α-allenic alcohols to 1,2-syn amino alcohol derivatives via iodocarbamation
作者:Richard W Friesen
DOI:10.1016/s0040-4039(00)97592-0
日期:1990.1
FRIESEN, RICHARD W., TETRAHEDRON LETT., 31,(1990) N0, C. 4249-4250