COMMUNICATIONS stein-Leopoldshafen (Germany), on quoting the depository number CSD-406925. Space group I4,/ucd, u = b = 1505.2(1), c = 4747.4(6) pm, V = 10756(2) A', Z = 8, pCDLEd =1.044 gcm-', 193 K, 5173 measured reflections, 2363 unique reflections, [R,,, = 0.0261, 1855 with FO>40(F,), 210 parameters,

A wide structural variety of S-allylic thiocarbamates 2 can be prepared in good yields by the rearrangement of O-allylic thiocarbamates 1 under three different conditions: thermal activation (neat, 120—150 °C), palladium(0) (25—65 °C), and palladium(II) catalysis (25—65 °C). Of the two possible regioisomers of unsymmetrical S-allylic thiocarbamates 2, those of higher thermodynamic stability can be prepared in high purity under either thermal activation or palladium(0) catalysis. Although the thermodynamically less stable regioisomers of 2 are, in general, hard to be prepared in high purity, some of them (e.g., 2d and 2h′) can be obtained with an exclusive or high selectivity by the catalysis of palladium(II). The stereoisomeric pair of 2j and 2j′ can be prepared selectively by the palladium(0)-catalyzed rearrangement of 1j and 1k, respectively. These reactions proceed with retention of configuration at the allylic stereocenters. S-Allylic (2) and S-alkyl thiocarbamates (7) undergo fragmentation to generate thiolates in the presence of inorganic bases (e.g., K2CO3, K2CO3·Et4N+I−) by heating in an aprotic solvent; the thus-formed thiolates react with aromatic iodides and vinyl bromides in the presence of palladium(0) complexes to furnish aryl and vinyl sulfides, respectively. A wide variety of aryl sulfides can be prepared in good yields irrespective of the kind of substituents and their substitution positions (o-, m-, p-) under conditions B [Pd(OAc)2, PPh3, K2CO3·Et4N+I−, dioxane, 100 °C]. Under conditions E [Pd(OAc)2, PPh3, Cs2CO3, dioxane, 100 °C], better yields result specifically for the sulfenylation of aromatic iodides bearing substituents having large Hammett σ constants.

No abstract

The thiocarbonyl group of monothiomaleimide 1 serves as a more reactive dienophile than the electron-deficient C=C double bond in the same molecule for the Diels-Alder reaction with dienes 2c-g and provides ortho-endo products 3 exclusively or predominantly over the other possible adducts 4-10.

Pd(II)-catalyzed intramolecular aminocarbonylation of olefins bearing many types of nitrogen nucleophiles has been examined under two typical conditions: acidic conditions [conditions A, typically PdCl(2) (0.1 equiv) and CuCl(2) (3.0 equiv) under 1 atm of CO at room temperature in methanol] and buffered conditions [conditions B, typically PdCl(2) (0.1 equiv) and CuCl(2) (2.3 equiv) under 1 atm of CO at 30 degrees C in trimethyl orthoacetate]. Among nitrogen nucleophiles, endo-carbamates 7 display distinctive reactivity: endo-carbamates 7a-k smoothly undergo intramolecular aminocarbonylation under conditions B to furnish 4-[(methoxycarbonyl)methyl]-2-oxazolidinones 8a-k in good yields, while they would not undergo the expected reaction under conditions A. Other nitrogen nucleophiles (exo-ureas 1, endo-ureas 3, exo-carbamates 5, and exo-tosylamides 9), on the other hand, satisfactorily undergo aminocarbonylation only under conditions A to give rise to 2, 4, 6, and 10, respectively, in good yields. Under conditions B, they are unreactive and provide either the expected products in poor yields or intractable mixtures of products. On the basis of this contrasting reactivity between endo-carbamates and other nitrogen nucleophiles, the chemoselective aminocarbonylation of 7l-o has been achieved; aminocarbonylation takes place at the endo-carbamate moieties to furnish 8l-o exclusively under conditions B, and aminocarbonylation occurs at the exo-carbamate, exo-urea, and exo-tosylamide moieties to yield 13a-d exclusively under conditions A.