4- one 1-oxide

Derivatives of 3-oxo-l,2,4-triazine 1-oxide undergo alkylation with various alkylating agents. Thus the reaction of 3-methoxy-l,2,4-triazine 1-oxide 20 with 2,3,5-tii-(9-benzoyl-/3-D-ribofuranosyl bromide, followed by the removal of the benzoyl protection with sodium methoxide, leads to an abnormal nucleoside 4-(/3-D-iibofuranosyl)-l,2,4-triazin-3(4//)-one 1-oxide 21 (73JOC3277). 

The reaction of the sodium salts of pyrido[2,3-e]-l,2,4-triazin-3(4//)-one 1-oxide 22 (Y = N) or l,2,4-benzotriazin-3(4//)-one 1-oxide 23 with acetobro-moglucose results in tetra-(9-acetyl derivatives of /3-D-glucopyranosides 24, 25 deacetylation of 25 gives nucleosides 26 (82JHC497). 

Methyl-1,2,4-benzotriazm-3(4//)-one 1-oxide 122 can be obtained in good yield by the diazotization of 121 to give 3-diazo-7-methyl-l,2,4-benzotriazine 1-oxide followed by the substitution of the diazo group with water (82JHC497). 

The photochemical behavior of a number of substituted derivatives of thiochroman-4-one 1-oxides has been examined by Still and coworkers192-194. These authors also report that rearrangement to cyclic sulfenates, with subsequent reaction by homolysis of the S—O bond, appears to be a particularly favorable process. For example, ultraviolet irradiation of a solution of 8-methylthiochroman-4-one 1-oxide (133) in benzene for 24h afforded a single crystalline product which was assigned the disulfide structure 134 (equation 54). More recently, Kobayashi and Mutai195 have also suggested a sulfoxide-sulfenate rearrangement for the photochemical conversion of 2,5-diphenyl-l,4-dithiin 1-oxide (135) to the 1,3-dithiole derivatives 136 and 137 (equation 55). 

Chemical shifts and coupling constants have been reported for ( )-3-benzylidenethiochroman-4-one 1-oxide and 1,1-dioxide (Figure 39). The 2-methylene unit appears as an AB system in the 1-oxide with J= 12.5 Hz but as a singlet in the 1,1-dioxide <1994T13113>. 

Figure 39 Chemical shift data for ( )-3-benzylidenethiochroman-4-one 1 -oxide and 1,1 -dioxide.

Thiochroman-4-one 1-oxide also fragments by a rDA reaction though now with the loss of ethene to afford a putative ketene sulfine 227. It is likely that a second fragmentation pathway of the molecular ion operates to afford the base peak, mlz 136 which subsequently eliminates CO to give mlz 108 (28%) rather than the direct loss of an oxygen atom from 227 (Scheme 16) <2002CH400>. 

The resolution of 3,4-dihydro-2/f-l-benzothiopyran-4-one 1-oxide has been achieved by capillary electrophoresis using heptakis-6-sulfato-/3-cyclodextrin or, better, its 2,3-diacetyl derivative as the chiral selector the i -sulfoxide migrated before the A-enantiomer <2001JSS766>. It has also been noted that (R)-thiochroman 1-oxide is eluted before the (d )-enantiomer from a Chiralcel cellulose tribenzoate column <2001TA1551> and a Daicel Chiralpak AD-H column using hexane/APrOH 90 10 has been used to resolve the (3.y,l. R) 249 and (3/ ,l A) 250 enantiomers of the substituted tetrahydrothiopyran-4-one <20050BC84>. 

The experimental IR and VCD spectra of thiochroman 1-oxide in CCI4 and CS2 solutions are in good agreement with DFT calculations, which predict population of the three conformations (Figure 55). Similarly, the two predicted conformations for thiochroman-4-one 1-oxide are present in the experimental spectra (Figure 56) <2002PCA10510>. 

The enantiomers of thiochroman 1-oxide have been obtained by oxidation of thiochroman in the presence of (R,R)-l,2-diphenylethane-l,2-diol (DPED) or L-diethyl tartrate. In the case of the enantioselective oxidation of thiochroman-4-one, (R,R)-DPED and (V,V)-DPED were used as the chiral inducers <2002CH400>. Fligh yields of both (—)-(R)-thiochroman 1-oxide and (—)-(R)-thiochroman-4-one 1-oxide and with enantioselectivities of 98% and 96%, respectively result from the reaction of H202 with the heterocycles when significant amounts of chloroperox-idase are used as catalyst <1998CH246>. 

H- and C-nmr spectral data tor the traii.s isomers of 1-phenyl-2,5-dimethylphosphorinan-4-one 1-oxide, 1-sulphide,... 

The ms of ais- and trans-1-phenyl-2,5-dimethylphosphorinan-4--one 1-oxide and 1-sulphide and 2,2-dimethyl-1-phenylphos-phorinan-4-one 1-oxide and 1-sulphide have been determined. 

The hydrolysis of 4-acetamido-1,1-dimethoxy-2,6-diphenyl--X -phosphorin gives 2,6-diphenyl-1-methoxy-1,2,3,4-tetra-hydro-X -phosphorin-4-one 1-oxide and 1,4-dihydro-2,6--diphenyl-1-methoxy-X -phosphorin-4-one 1-oxide, which can be converted into 2,6-diphenyl-1,1,4-trimethoxy-X --phosphorin and characterized as the stable crystalline tricarbonylchromium complex (32) (Dimroth and M. Liickoff, Ber., 1980, 113, 3313). 

Reaction of 8 with triethyloxonium tetrafluoroborate furnishes 3-ethoxy-1 -phenyl-1,2,4-thiadi-azin-5(4//)-one 1-oxide (9). Treatment of 9 with silver(I) nitrate in alkaline solution affords the silver salt of 9 which reacts with iodoethane to yield 3,5-diethoxy-l-phenyl- l H-, 2,4-thiadi-azine 1-oxide (10).21... 

As expected, treatment of l,5-diphenyl-U , 2,4-thiadiazin-3(4//)-one 1-oxide (122) with phosphorus oxychloride yields the 3-chloro derivative (123) (Scheme 14) which under aqueous alkaline conditions reverts to the 3(4//)-one <90JCS(Pi)447>. 

Taylor has also shown that treatment of 3-methoxycarbonylthian-4-one 1-oxide with acetic anhydride under reflux furnishes a product in which P-carbon oxidation and ring contraction have taken place (Scheme 4.68). 

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