Generation of 1,3-dipoles containing carbon, nitrogen, sulphur and phosphorus

Zhu, Shuguang (1997) Generation of 1,3-dipoles containing carbon, nitrogen, sulphur and phosphorus. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Most of the known 1,3-dipoles of propargyl-allenyl type (A≡B⁻-C˙) are composed of carbon, nitrogen and oxygen. Very few 1,3-dipoles of this type contain atoms from the third or lower periods. The nitrile sulphide (R-C≡N⁻-S˙), a recently discovered family of 1,3-dipoles, incorporates sulphur in its π manifold. Our attempts to isolate this very reactive intermediate proved that a bulky group, adamantyl (C₁₀H₁₅-), could not appreciably stabilize it. -- Our synthesis of the bis(nitrile sulphides) or their synthetic equivalents started with the adamantyl (1,3-C₁₀H₁₄-) substituent. 1,3-Bis(1’,3’,4’-oxathiazol-2’-one-5'-yl)-adamantane 3-28a, the precursor for the 1,3-bis(nitrile sulphide)-adamantane 3-20a, was prepared and its cycloaddition reactions to DMAD and 1,3-bis(cyano)adamantane were examined. It was found that the bis(nitrile sulphide) 3-20a had a comparable reactivity to that of adamantyl nitrile sulphide 2-6. 1,8-Bis(1’,3’,4'-oxathiazol-2'-one-5’-yl)-octane 3-28b, another precursor for bis(nitrile sulphide) 3-20b, was also prepared but others such as 1,1-bis(1',3',4'-oxathiazoI-2'-one-5'-yl)-methane 3-28c and 1,4-bis(1',3',4'-oxathiazol-2’-one-5’-yl)-benzene 3-28d could not be synthesized from similar reactions of the corresponding amides with CISC(O)CI due to the strong hydrogen bonding existing in the amides. The conjugated phenyl isothiazolyl oxathiazolones 3-41 and 3-42 were synthesized and their cycloaddition reactions to dipolarophiles were examined. The possibility of producing the poly(isothiazoles) from these oxathiazolones will be discussed. -- A novel synthetic route to the precursor, 1,3,4-oxathiazol-2-one, has been discovered. A better starting material, N,O-bis(trimethyIsiIyl)carbonamide 4-7, was used to replace the amide in the reaction to avoid the strong hydrogen bonding. Several oxathiazolones such as 5-methyl-1,3,4-oxathiazol-2-one 4-4a, 5-(4'-biphenyl)-1,3,4-oxathiazol-2-one 4-4c, 1,4-bis(1’,3',4'-oxathiazol-2'-one-5’-yl)-benzene 4-4d and 4,4'-biphenyl-bis(1”,3",4"-oxathiazol-2”-ones) 4-4e were prepared through the new route. -- The reactions of amides 5-21 with C1SC(O)CI were proposed to synthesize the heterocycles 5-22 which were supposed to be the precursors to the new 1,3-dipoles 5-23. The reactions of p-toluenesulfinamide/N,N-bis(trimethylsilyl)-p-toluenesulfinamide 5-24 with CISC(O)CI did not give the expected precursor 5-22 but p-toIuenedisulfide 5-25, p-toluenethiol-p-toluenesulfonate 5-26 and cyanuric acid 5-27. Benzenesulfonamide/p- toluenesulfonamide with CISC(O)CI did not give any product but the amides themselves. A new reaction of adamantyl phosphaalkyne 5-37 with elemental sulphur with or without Et₃N present in toluene was tested for the synthesis of phosphaalkyne sulphide 5-38.

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