Identification and Synthesis of New γ-Lactones from Tuberose Absolute (Polianthes tuberosa)

Six unsaturated γ-lactones, (Z)-5-octen-4-olide ( 1 ), (Z)-5-decen-4-olide ( 2 ).(Z)-6-nonen-4-olide ( 3 ), (Z)-6-dodecen-4-olide ( 4 ), (Z, Z)-6,9-dodecadien-4-olide ( 5 ), and tuberolide ( 6 ) have been identified for the first time in tuberose absolute (from Polianthes tuberosa L.). All structures were corroborated by synthesis and all, except 3 and 4 , are new.

1 The name ‘tuberolactone’ has been suggested for (Z, Z)-2,7-decadien-5-olide [1]. We propose the name ‘tuberolide’ for the bicyclic lactone 6 . (IUPAC name (1R*,5S*,Z)-6-(2′-pentenyl)-2-oxabicyclo[3.3.0]octan-3-one).

An improved method for the stereoselective synthesis of (±)-cis-bicyclo [4.3.0]-non-3-en-7-one ( 23 ) by an AlCl₃-catalyzed Diels-Alder reaction is reported.     

Rh(I)-catalyzed mild intramolecular [4+2] cycloaddition reactions of ester-tethered diene-yne compounds

The cationic rhodium(I) species derived from [Rh(COD)Cl]₂ and AgSbF₆ efficiently catalyze intramolecular [4+2] cycloadditions of ester-tethered 1,3-diene-8-yne derivatives such as 2-propynyl penta-2,4-dienoate and 2,4-pentadienyl propiolate derivatives in fluorinated alcohols.     

Addition of mercaptans to acetylenic γ-hydroxy ketones

Conclusions Both the nucleophilic and the free radical addition of n-butyl mercaptan to acetylenic-hydroxy ketones (1,1-disubstituted derivatives of 2-pentyn-1-ol-4-one) lead to the formation of the corresponding 1,1-disubstituted derivatives of 2-butylthio-2-penten-1-ol-4-one in 41–65% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1669–1670, July, 1973.     

Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. X. Synthesis of N,N-disubstituted 6-alkyl-4-amino-3,3-dichloro-3,4-dihydro-2H-pyran-2-ones and of 6-alkyl-4-amino-3-chloro-2H-pyran-2-ones

Cycloaddition of dichloroketene to N,N-disubstituted 1-amino-4-methyl-1-penten-3-ones and 1-amino-4,4-dimethyl-1-penten-3-ones occurred in moderate to fair yield only in the case of aromatic N-substitution to give N,N-disubstituted 6-alkyl-4-amino-3,3-dichloro-3,4-dihydro-2H-pyran-2-ones, which were dehydrochlorinated with DBN to afford in good yield N,N-disubstituted 6-alkyl-4-amino-3-chloro-2H-pyran-2-ones. In the case of aliphatic N,N-disubstitution, cyclo-addition led directly to 6-alkyl-4-dialkylamino-3-chloro-2H-pyran-2-ones only for N,N-disubstituted 1-amino-4,4-dimethyl-1-penten-3-ones. The reaction between 1-dimethylamino-4-methyl-1-penten-3-one and dichloroketene gave 3-chloro-4-dimethylamino-3,6-dihydro-6-isopropylidene-2H-pyran-2-one in low yield.     

Fluorinated 1,3-diketones, 2-trifluoroacetyl phenols and their derivatives: versatile reactants in phosphorus chemistry

The role of fluorinated β-diketones, their tautomers (keto–enols) and their derivatives as reagents towards λ³P compounds is reviewed, including 2-trifluoroacetyl phenols, possessing formally a keto–enol system, and their derivatives. In an ‘insertion’ reaction phosphine and the keto–enol tautomers of 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione furnished primary (S) or (R) α-hydroxy phosphines, whose enol functions probably isomerized the corresponding keto compounds. Further addition and isomerisation furnished 1,3α,5,7β-tetrakis(trifluoromethyl)-2-phospha-6-oxa-9-oxabicyclo[3.3.1]-nonan-3β,7α-diol and 1,7-trifluoromethyl-3,5-methyl-2,4,8-trioxa-6-phophaadamantane, exclusively one diastereomer in each case. The main mechanistic feature of these reactions is a consecutive diastereoselective hemiketal cyclization. 1,1,1,5,5,5-Hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, as well as 2-trifluoroacetyl phenol and its imino derivatives reacted diastereospecifically with phosphonous acid dichlorides, RPCl₂ to give in a concerted mechanism thermally stable tricyclic λ⁵σ⁵P phosphoranes containing two five-membered rings and one six-membered ring. Surprisingly, the two CF₃ groups bonded to an sp³-hybridized carbon were in a cisoid arrangement having closest non-bonding FF distances of 301.4 or 273.5 pm. These findings reflect the ‘through space’ F---F coupling constants of the tricyclic phosphoranes (J_FF=4.0–7.0 Hz), in solution. 4,4,4-Trifluoro-3-hydroxy-1-phenyl-butan-1-one and methyl or phenyl phosphonous acid dichlorides gave similar tricyclic phosphoranes decomposing at ambient temperature to furnish 1,2λ⁵σ⁴-oxaphospholanes and (E)-1,1,1-trifluoro-4-phenyl-but-2-en-4-one. Dialkylphosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione reacted to give either the (Z)-enol phosphonates or the respective γ-ketophosphonates from which in two cases four diastereomeric 2-oxo-2,5-dialkoxy-3,5-bis(trifluoromethyl)-3-hydroxy-1,2λ⁵σ⁴-oxa-phospholanes were obtained. 2-Trifluoroacetyl cyclohexanone, 4,4,4-trifluoro-3-trimethylsiloxy-1-phenylbutan-1-one, 1-benzoyl-2-trifluormethyloxirane, 1-benzoyl-2-trifluoro-methylaziridine, 2-trifluoroacetyl-1-trimethylsiloxybenzene and (trifluoroacetyl-1-phenyl) diethyl phosphate reacted with tris(trimethylsilyl) phosphite to give functionalized α-trimethylsiloxy phosphonates, which could easily be transferred into the respective phosphonic acids. In the case of an oxirane and an aziridine ketone no ring cleavage was observed. For 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone and 1,1′-(2-trimethylsiloxy-5-methyl-m-phenylene)-bis-ethanone benzoxaphospholanes were obtained. Trialkyl phosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione furnished cyclic phosphoranes containing the 3-hydroxy-3,5-bis(trifluoromethyl)-1,2λ⁵σ⁵-oxaphospholene structural element, stable at ambient temperature only in the case of one cyclic phosphite precursor. (E)-1,1,1-Trifluoro-4-phenyl-but-2-en-4-one and trimethylphosphite reacted to form 1,2λ⁵σ⁵-oxaphosphol-4-ene as the sole product. Results similar to the reaction of 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone with diethyltrimethylsilylphosphite were obtained for trimethylphosphite and 2-trifluoroacetyl phenol where a deoxygenated phosphorane was found, easily hydrolyzed to give the respective phosphonic acid. With dialkylisocyanato phosphites and the keto components, 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, 4,4,4-trifluoro-1-phenyl-1,3-butandione, 2-trifluoroacetyl cyclohexanone, 2-trifluoroacetyl phenol and 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone reacted in a ‘double’ cycloaddition to form bicyclic phosphoranes containing the 4,8-dioxa-2-aza-1λ⁵σ⁵-phosphabicyclo[3.3.0]-oct-6-en-3-one ring system; for the imino derivatives of 2-trifluoroacetyl phenol a corresponding 8-oxa-2,4-diaza- system was generated. For (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one however, a cyclic spiroimino phosphorane was obtained which underwent a [2+2] cyclodimerization to form a diazadiphosphetidine. Dimethylpropynyl phosphonite and 1,1,1,5,5,5-hexafluoropentan-2,4-dione yielded diastereoselectively a bisphosphorane, namely 1,4-bis(trifluoromethyl)-3,6-dioxa-2,2,7,7-tetramethoxy-2,7-di(1-propynyl)-2,7-diphosphabicyclo[2.2.1] heptane. When trimethylsilanyl–phosphenimidous acid bis-trimethylsilanyl–amide, Me₃SiN=PN(SiMe₃)₂, was allowed to react with 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one, 2-trifluoroacetyl cyclopentanone, 2-trifluoroacetyl phenol and its imino derivatives, 2-imino-1,2λ⁵σ⁴-oxaphospholenes were found containing two diastereomers in each case, which added hexafluoroacetone across the P=N bond to give 1,3,2λ⁵σ⁵-oxazaphosphetanes.     

Identification of Twenty-one Novel Constituents of Oriental Tobacco Flavour (Nicotiana tabacumL.) including (E)-3-methyl-non-2-en-4-one,pentadecan-15-olide, 8α, 13:9α, 13-diepoxy-15, 16-dinorlabdane, (Z)-octadec-9-en-18-olide,and (E)-2-ethylidene-6, 10, 14-trimethyl-pentadecanal

Investigation by gas liquid chromatography of a small but organoleptically typical subfraction of Oriental tobacco condensate led to the identification of 47 compounds. Of these 21 have hitherto not been reported as Oriental tobacco constituents, and 14 appear to be novel to all tobacco types. The latter are (E)-3-methyl-non-2-en-4-one ( 1 ), (E)-1-(2, 3, 6-trimethylphenyl)-but-2-en-1-one ( 3 ), pentadecan-15-olide ( 12 ), 8α, 13:9α, 13-diepoxy-15, 16-dinorlabdane ( 17 ), (Z)-octadec-9-en-18-olide ( 18 ), (E)-2-ethylidene-6, 10, 14-trimethylpentadecanal ( 21 ), the norlabdanoids 9 , 10 , 11 , 14 , 15 , 16 , tridecan-2-one, and 2-phenylethyl isovalerate. The macrolides 12 and 18 represent the first musk compounds detected in tobacco. Identification were made by direct comparison (MS. and/or ¹ H-NMR./IR.) with the authentic chemicals synthesized whenever necessary.     

Hydrosilylation of 2-(2-Propynyl)-2,3-dihydro-1,2-benzothiazol-3-one 1,1-Dioxide with 1-Alkynyl(dimethyl)- and Bis(1-alkynyl)methylsilanes

Hydrosilylation of 2-(2-propynyl)-2,3-dihydro-1,2-benzothiazol-3-one 1,1-dioxide with 1-alkynyldimethyl- and bis(1-alkynyl)methylsilanes of the general formula Me _n HSi(C=-CR)₃-n (n = 1, 2) in the presence of H₂PtCl₆ (Speier's catalyst) occurs in a nonregioselective but stereoselective fashion, yielding mixtures of the corresponding trans-- and -adducts. The fraction of the latter ranges from 50 to 70%, depending mainly on the substrate nature rather than on the nature of substituent at the triple bond of the reagent.     

Reaction of 6-methyl-6-p-tolyl-4-ethoxy-5,6-dihydro-pyran-2-one1 with perchloric acid

6-Methyl-6-p-tolyl-4-ethoxy-5,6-dihydro-pyran-2-one (1) undergoes decarboxylative elimination with perchloric acid in ether to give 4-p-tolyl-3-penten-2-one (3), the structure of which has been confirmed through an unambiguous synthesis.

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Reaktion von 6-Methyl-6-p-tolyl-4-ethoxy-5, 6-dihydro-pyran-2-on mit PerchlorsäureKurze Mitteilung

Zusammenfassung Die Titelverbindung (1) ergibt mit Perchlorsäure unter decarboxylierender Eliminierung 4-p-Tolyl-3-penten-2-on (3). Die Struktur von3 wurde mittels eines eindeutigen Syntheseweges festgelegt.

     

Ringerweiterung von sechs- zu neungliedrigen Heterocyclen: Umsetzung von 3-(Dimethylamino)-2,2-dimethyl-2H-azirin mit 3,4-Dihydro-2H-1,2,4-benzothiadiazin-3-on-1,1-dioxiden

Ring Enlargement of Six- to Nine-Membered Heterocycles: Reaction of 3-(Dimethylamino)-2,2-dimethyl-2H-azirine with 3,4-Dihydro-2H-1,2,4-benzothiadiazin-3-one 1,1-Dioxides Reaction of 3-(dimethylamino)-2,2-dimethyl-2H-azirine ( 1 ) and N-substituted 3,4-dihydro-2H-1,2,4-benzothiadiazin-3-one 1,1-dioxides ( 4 ) in CHCl₃ yields 3-(dimethylamino)-4,5,6,7-tetrahydro-1,2,5,7-benzothiatriazonin-6-one 1,1-dioxides 5 , a novel nine-membered heterocyclic system, by ring enlargement (Schemes 2 and 4). In refluxing MeOH, the heterocycle 5a rearranges to give the N-[1-methyl-1-(1,1-dioxo-4H-1,2,4-benzothiadiazin-3-yl)ethyl]-N′, N′-dimethylurea 10 . The three isomeric 2-(methylamino)benzenesufonamides 8,9 , and 11 (Scheme 3) are obtained by naBH₄ reduction of 5a and 10 , respectively. Mechanisms for the thermal isomerization 5a → 10 and the NaBH₄ reduction of 5a are proposed in Schemes 5 and 6.     

Synthesis of the Enantiomerically Enriched Macrocyclic Lactones (+)-(S)- and (−)-(R)-Phoracantholide I and (+)-(S)-Tetradecan-13-olide

Synthesis of two naturally occurring macrocyclic lactones is described. (?)-(R)-Phoracantholide I ((?)- 1 ; Scheme 2) was synthesized by asymmetric and chemoselective reduction of the side-chain C?O group of (?)4-(1-nitro-2-oxocyclohexyl)butan-2-one ((?)- 6 ) with (R)-Alpine-Hydride (47% ee). It was shown that the formation of only one diastereoisomer of the hemiacetal 5 , by methylation with (i-PrO)₂TiMe₂ of ketoaldehyde (?)- 2 is thermodynamically controlled. (+)-(S)-Tetradecan-13-olide ((+)- 10 ) was obtained by reduction of diketone (±)- 11 with optically active borohydrides followed by denitration (Scheme 3).     

Butanolide und Butenolide durch intramolekulare En-Reaktion bei der Thermolyse von Propargyl-propiolaten

Butanolides and Butenolides by Intramolecular Ene-Reaction during Thermolysis of Propargyl Propiolates Gas-phase flow thermolysis of 2-butynyl propynoate ( 1 ) and 2-propynyl 2-butynoate ( 2 ) at 550° afforded 3-ethynyl-2-methyl-2-buten-4-olide ( 4 , 85%) and 2-ethynyl-3-methyl-2-buten-4-olide ( 5 , 80%), respectively. Their formation presumably entails an ene reaction between the methylacetylenic and the acetylenic functions of the diyne esters 1 and 2 to give the two methyliden-vinyliden-butanolides 10 and 11 as intermediates, followed by a [1,5]-H shift to 4 and 5 . At 400–450°, the gas phase flow thermolysis of 1 and 2 led to the dimers 16 (77%) and 17 (6%), respectively. These products resulted from the Diels-Alder dimerization of the above mentioned intermediates 10 and 11 . The regioselectivity of this dimerization is determined by a ‘head-to-head’ approach, with the double bond conjugated to the carbonyl group acting as the dienophile in both cases. The low yield of 17 from 2 is probably due to a further Diels-Alder reaction of the dimer 17 with its precursor 11 , yielding a trimer 18 (8% isolated). This process is not possible when starting with 1 , which explains the higher yield of 16 . The gas phase flow thermolysis of 2-butynyl 2-butynoate ( 3 ) at 550° afforded a mixture of four isomeric products, namely the two monocyclic ethynyl-butenolides 6 and 7 and the two bicyclic vinyl-butenolides 8 and 9 . The formations of 6–9 are also rationalizable by initial ene-reactions, in this case two alternative ones, each involving one of the two CH₃ groups of 3 . This leads to two alkylidene-vinylidene-butenolides, namely 12 and 13 . A [1,5]-H shift converts 12 into 6 and 13 into 7 . A competing alternative [1,5]-H shift transforms both 12 and 13 to the triene 14 , which electrocyclizes to the cyclohexadiene 15 . The latter undergoes two alternative [1,5]-H shifts to yield 8 and 9 .     

Synthese von racemischen Aminozuckersäure-lactonen: xylo- und lyxo-2,3-Diacetylamino-5-acetoxypentan-4-olid und -2,3,5-Triacetylaminopentan-4-olid

Synthesis of Racemic Aminosugar Lactones: xylo- and lyxo-2,3-Diacetylamino-5-acetoxypentan-4-olide and -2,3,5-Triacetylaminopentan-4-olide Starting with 5-hydroxy-2-penten-4-olide ( 1 ), the tricyclic intermediate 4 was prepared via the chloride 2 , the acyl azide 3 , and an intramolecular nitrene addition (Scheme 3). Azide ion opened the aziridine ring in 4 at C(α) to give 5 , which was transformed via 7 into one of the title compounds, the triacetylated diamino-hydroxy-lactone 13 (Scheme 4). An alternative conversion of 4 into 13 involved the synthesis of the N-acetylaziridine 10 , the opening of the 3-ring of 10 with N to form 12 , and a final reductive acetylation (Scheme 5). The third N-substituent was introduced at C(δ) of 13 by the following sequence: hydrolysis of the AcO group (→ 14 ), mesylation (→ 15 ), substitution by N (→ 16 ), and reductive acetylation to yield the other title compound, the triacetylated triaminolactone 17 (Scheme 6). Since the ring opening of aziridines by nucleophiles occurs by inversion, the primary products 5a and 12a of the N reactions as well as the substances derived from them, i.e. 6a , 7a , and 13a - 17a , have the xylo-configuration ( a -series). Under some of the reaction conditions, the primary xylo-products suffered a partial epimerization at C(α) to yield mixtures containing the corresponding lyxo-products ( b -series): The equilibrium between the xylo- and lyxo-isomers was estimated for 5a/5b =1:3, 12a/12b =5:2, 13a/13b =3:1, and 16a/16b =2:1. Since the stereoisomers of the a - and the b -series were always separable, the other lyxo-products, i.e. 6b , 7b , could be prepared from 5b and 12b .     

Synthesis of functional derivatives of trifluoromethylpyrimidines from acetylacetone,trifluoroacetonitrile, and aryl isocyanates

1, 1,1-Trifluoro-2-amino-3-acetyl-2-penten-4-one was obtained by the addition of acetylacetone to trifluoroacetonitrile in the presence of catalytic amounts of nickel acetylacetonate. The reaction of 1,1,1-trifluoro-2-amino-3-acetyl-2-penten-4-one with aryl isocyanates gave 1-aryl-5-acetyl-6-methyl-4-trifluoromethyl-1H-pyrimidin-2-ones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2639–2642, November, 1991.     

Convenient synthesis of linear pyrano[3,2-g]-, [2,3-g]- and angular pyrano[3,2-f]coumarins from 4[(1,1-dimethyl-2-propynyl)oxy]phenol

An easy preparation of new 4-alkoxycarbonyl angular and linear pyranocoumarins starting from 4-[(1,1-dimethyl-2-propynyl)oxy]phenol and their transformation to the known coumarins xanthyletin, 8,8-dimethylpyrano[3,2-f]chromen-3(8H)-one and 7,7-dimethylpyrano[2,3-g]chromen-2(7H)-one is described.     

Zur Oxidation von 1,2-Thiazolen: Ein einfacher Zugang zu 1,2-Thiazol-3(2H)-on-1,1-dioxiden

Oxidation of 1,2-Thiazoles; A Convenient Approach to 1,2-Thiazol-3(2H)-one 1,1-Dioxides The 1,2-thiazoles obtained from 3-chloroalk-2-enals and ammonium thiocyanate ( 7 → 9 , Scheme 1) are easily transformed to 1,2-thiazol-3(2H)-one 1,1-dioxidcs 10 on treatment with H₂O₂ in AcOH at 80°. Hydrogenation of 10 in AcOH yields the corresponding saturated 1,2-thiazolidin-3-one 1,1-dioxides 16 (Scheme 3). Cycloalka[c]-1,2-thiazoles 18 are prepared from 2-[(thiocyanato)methyliden]cycloalkan-1-ones and ammonia (Scheme 4). Surprisingly, oxidation of 18a with H₂O₂ in AcOH yields the tricyclic oxaziridine 19.     

Novel Ketones from Roman Camomile Oil

β-Damascenone ( 1 ) has been identified in the fraction of Roman camomile (Anthemis nobilis) oil that contains homologues of carvotanacetone. 5-(3-Furyl)-2-methyl-1-penten-3-one ( 2 ), (E)-1-(2,6-dimethylphenyl)-2-buten-1-one ( 8 ), 4-isopropenylbenzaldehyde ( 4 ), were also identified and synthesized.     

Theoretical Study of 3-Penten-2-one Complexes of Iron and Chromium Subgroup Metals with Various Modes of the Enone Coordination

The calculated parameters of the steric and electronic structure and shielding constants of ²- (3-penten-2-one)Fe(CO)₄, ²-(3-penten-2-one)M(CO)₅, ⁴-(3-penten-2-one)Fe(CO)₃, and ⁴-(3-penten-2-one) ·M (CO)₄ (M = Cr, Mo, W) nicely agree with the experiment. Coordination of the -enone with transition metals significantly distorts the conjugation between the C = C and C = O bonds.     

Synthesis of 4-β-D-arabinofuranosyl-5,6-dihydro-2H-1,2,4-thiadiazin-3-one 1,1-dioxide and x-ray diffraction analysis of its 2′,3-anhydro precursor

Reaction of 2-amino-3′,5′-bis(O-tert-butyldimethylsilyl)-β- D -arabinofuran[1′,2′:4,5]-2-oxazoline with 2-chloroethylsulfonyl chloride in the presence of sodium bicarbonate followed by removal of the protecting groups gave 2′,3-anhydro-4-β- D -arabinofuranosyl-5,6-dihydro-2H-1,2,4-thiadiazin-3-one 1,1-dioxide ( 5 ), which by treatment with ammonia was converted to 4-β- D -arabinofuranosyl-5,6-dihydro-2H-1,2,4-thiadiazin-3-one 1,1-dioxide ( 6 ). The structure of compound 5 was unequivocally established by means of an x-ray diffraction analysis. The compound crystallized in the space group P2₁2₁2₁ with unit cell dimensions a = 5.883(3), b = 9.352(2), c = 18.769(7) Å, Z = 4. Its structure was established by direct multisolution techniques and refined by the full matrix least squares method to a final R value of 0.058 for the 1515 reflections observed.     

Regioselectivity in the diels-alder reactions of α-pyrones with alkynes

4-Ethyl-5-methyl-6-methylthio-2(H)-pyranone (4) undergoes Diels-Alder reactions with ethyl hexynoate (5), 3-heptyn-2-one (6), ethyl propiolate (7), and 3-butyn-2-one (8) to afford substituted benzenes with high regioselectivity upon extrusion of CO₂. 4-Ethyl-5,6-dimethyl-(1), 4-ethyl-3,6-dimethyl-(2) and 4-ethyl-5-methyl-(2H)-pyranone (3) gave excellant to good regioselectivity with internal alkynes 5 and 6 and poor regioselectivity with terminal alkynes 7 and 8. MNDO calculations have been carried out on the pyrones and alkynes and qualitative FMO analysis correctly predicts the major products.     

Synthesis of 2H-1,4-thiazin-3(4H)-one 1-oxide and 2H-1,4-thiazin-3-(4H)-one 1,1-dioxide,structural analogs of uracil

The synthesis of 1,4-thiazine 1-oxide and 1,1-dioxide analogs of the antibiotic emimycin is described. Reaction of methylthioglycolate with 1-bromo-2,2-diethoxyethane gave methyl (2,2-diethoxyethylthio)acetate ( 2 ). Treatment of 2 with methanolic ammonia followed by cyclization furnished 2H-1,4-thiazin-3(4H)-one ( 5 ). Oxidation of 5 with m-chloroperoxybenzoic acid converted it to 2H-1,4-thiazin-3(4H)-one 1-oxide ( 6 ). Oxidation of 2 with potassium permanganate, followed by treatment with methanolic ammonia, and cyclization gave 2H-1,4-thiazin-3(4H)-one 1,1-dioxide.