Hypervalent sulfur heterocycles

Figure 10 Typical structural types of hypervalent sulfur heterocycles.

Heterocycles with Hypervalent Sulfur or Selenium at the 5 5 Ring Junction 847... 

Halogen abstraction from hypervalent sulfur halides has also been reported for the imidazol-2-ylidenes (IV) (Scheme 8.22). This reaction gives a nice example of the synthetic utihty of V-heterocyclic carbenes. Indeed, this adduct is the first structurally characterized derivative featuring the chlorosulfite ion (SO2CI ). ... 

The 1,2,4-thiadiazolidine (369) and the 1,2,4-dithiazolidine (370) are interconvertible in the presence of electrophilic nitriles and give the l,2,4-thiadiazoline-5-ones (371) as products (Scheme 61) (91JOC3268). It is suggested that the reaction goes by a consecutive cycloaddition - elimination mechanism via hypervalent sulfur intermediates in which the nitrile approaches in the plane of the heterocycle. 

The nonclassical structure of sulfur heterocycles, including thiepine with hypervalency of sulfur, was investigated by MP2(full)/6-31G and B3LYP/6-31G calculations <1997JOC1766>. It was shown that both MP2 and DFT methods adequately predict the molecular geometries. The thiepine-1-SIV (A4cr2-thiepine) 12 with... 

The reactions of thiadiazolopyrimidines 58 (R = Me, allyl) with ethoxycarbonyl isothiocyanate and CS2 gave heterocycle 59 via thermal decomposition of 1 1 cycloadducts, which have a hypervalent sulfur (Equation 10). The mechanistic and reactivity features of these reactions were described <2004JHC99>. 

Reaction kinetics for the interaction of 5-alkyliminothiatriazoles 52 or 58 with heterocumulenes, nitriles, ketones, imines, or other dipolarophiles a=b show that the decomposition of the thiatriazole is bimolecular, and new heterocyclic five-membered rings 71 are formed (Scheme 15). The term masked 1,3-dipolar cycloaddition was used by L abbe and co-workers for this type of reaction <1978JOC4951>, the thioimidate function being the masked 1,3-dipole. The reaction is thought to involve a thiapentalenic intermediate 70 with hypervalent sulfur. The product 71 is itself a masked dipole and often further reactions take place. 

Keywords Benziodoxoles Hypervalency Hypervalent Hypervalent boron Hypervalent bromine Hypervalent heterocycles Hypervalent iodine Hypervalent silicon Hypervalent sulfur Iodine heterocycles... 

In a more recent work, Kawashima reported the preparation and structural studies of a series of four-membered lO-S-4 and lO-S-5 heterocycles 51—54 (Figure 11) (2011PSS1046). These compounds containing a tetra-coordinated or pentacoordinated hypervalent sulfur atom together with other heteroatoms were isolated as thermally stable products and structurally... 

Figure 11 Four-membered heterocycles with a hypervalent sulfur atom.

Kita Y, Egi M, Okajima A, Ohtsubo M, Takada T, Tohma H (1996) Hypervalent iodine(lll) induced intramolecular cyclization of substituted phenol ethers bearing an alkyl azido side-chain - a novel synthesis of quinone imine ketals. Chem Commun 1491-1492 Kita Y, Egi M, Ohtsubo M, Saiki T, Takada T, Tohma H (1996) Novel and efficient synthesis of sulfur-containing heterocycles using a hypervalent iodine(lll) reagent. Chem Commun 2225-2226... 

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