Dihydrothiophene dioxides, reactions

Dihydrodithiin sulphoxides, synthesis of 243 Dihydrothiophene dioxides, reactions of 653 /(,/( -Dihydroxyketones 619 Dimerization, photochemical 877, 884 Dimethyl sulphoxide anion of - see Dimsyl anion hydrogen bonding with alcohols and phenols 546-552 oxidation of 981, 988 photolysis of 873, 874, 988 radiolysis of 890-909, 1054, 1055 self-association of 544-546 Dimsyl anion... 

Extrusion of sulfur dioxide from a ring-fused dihydiothiophene derivative provides an exceptionally easy method for the preparation of heterocyclic o-dimethylene compounds. These compounds are valuable intermediates in intermolecular Diels-Alder reactions. This extrusion method was used to prepare the o-dimethylene compounds 44-46 <95CC1349> as well as quinolinone derivative 47 <95TL5983>. TTie dihydrothiophene dioxide moiety also played an important role in the formation of the intramolecular Diels-Alder reaction of N-substituted pyrrole 48 <95CC807>. 

Another cheletropic reaction is the addition of sulphur dioxide under pressure to the hexa-2,4-dienes (134 and 136) to give the dihydrothiophen dioxides (135 and 137 respectively).129 These reactions are easily reversible simply by heating... 

Cycloaddition reactions of 1,3-dienes with sulfur dioxide, unlike its mono and bis imino derivatives, usually produce five-membered ring 2,5-dihydrothiophene dioxides rather than Diels-Alder adducts [Eq. (36)]. 

Hogeveen and Heldeweg found a rare example of a Diels-Alder reaction with sulfur dioxide where the [4 + 2] adduct is reasonably stable. Addition of sulfur dioxide to diene 76 at low temperature yielded [4 -I- 2] adduct 77 as the kinetic product. At temperatures above 2(J C products resulting from the dihydrothiophene dioxide 78 were observed (Scheme 1-XVI). 

Addition of SO 2 to hexadienes This reaction carried out under pressure gives dihydrothiophene dioxides or thermal explosion ofS02. ... 

Reaction with 2,5-Dihydrothiophene 1,1-Dioxide. 2,5-Dihydrothiophene 1,1-dioxides are known to be converted into 1,3-dienes after thermal displacement of sulfur dioxide. Reaction in situ with Fe2(CO)9 offers a general preparation of highly functionalized tricarbonyl(Ti -buta-l,3-diene)iron(0) complexes (50) (eq 31). ... 

Production. Sulfolane is produced domestically by the Phillips Chemical Company (Borger, Texas). Industrially, sulfolane is synthesized by hydrogenating 3-sulfolene [77-79-2] (2,5-dihydrothiophene-l,1-dioxide) (2), the reaction product of butadiene and sulfur dioxide ... 

This category is represented in the facile reaction of o-phenylenediamine (408) with 4-benzoyl-5-phenyl-2,3-dihydro-2,3-thiophenedione (409) (in toluene at 20°C for 30 min) to afford 3-(a-benzoyl-p-mercaptostyryl)-2(l//)-qumoxalinone (410) in 98% yield " also in the complicated reaction of 3-methyl-2,2,4-trinitro-2,5-dihydrothiophene 1,1-dioxide (411) with 2 equiv of ethyl 4-aminobenzoate (412) (in acetonitrile but no further details) to give ethyl 2-(p-ethoxycarbonylphenyl)-3-(l-methyl-2-nitrovinyl)-6-quinoxalinecarboxylate (413) in 51% yield.Several... 

Dihydrothiophene-1,1-dioxides (42) and 2,17-dihydrothiepin-1,1-dioxides (43) undergo analogous 1,4 and 1,6 eliminations, respectively (see also 17-38). These are concerted reactions and, as predicted by the orbital-symmetry rules (p. 1067), the former is a suprafacial process and the latter an antarafacial process. The rules also predict that elimination of SO2 from episulfones cannot take place by a concerted mechanism (except antarafacially, which is unlikely for such a small ring), and the evidence shows that this reaction occurs by a non-concerted pathway.The eliminations of SO2 from 42 and 43 are examples of cheletropic reactions, which are defined as reactions in which two a bonds that terminate at a single atom (in this case the sulfur atom) are made or broken in concert. 

Under certain basic conditions 2,5-dihydrothiophene 1,1-dioxides undergo ring opening reactions - and the resulting buta-l,3-dienyl sulfinate ions may be alkylated... 

The most synthetically useful cheletropic elimination involves 2,5-dihydrothiophene-1,1-dioxides (sulfolene dioxides). At moderate temperatures they fragment to give dienes and sulfur dioxide.301 The reaction is stereospecific. For example, the dimethyl derivatives 22 and 23 give the E,E- and Z,E-isomers of 2,4-hexadiene, respectively, at temperatures of 100°-150°C.302 This stereospecificity corresponds to disrotatory elimination. 

Figure 1. Reaction of 3,4-Bis(bromomethyl)-2,5-Dihydrothiophene-l, i-Dioxide with Monosubstituted Aniline.

The reaction of o-halomethylene benzyl halides, l,4-dihalobut-2-enes, cyclo-2-hexenols or 2,5-dihydrothiophene-l,1-dioxides with Na2Fe(CO)4 or Fe2(CO)9 results in the formation of (diene)Fe(CO)3 complexes108. In each case, the precursor is transformed in situ into the free diene ligand, followed by complexation. 

Intramolecular [4 + 2] cycloaddition reactions of enamides have provided a route to hydroindole and hydroquinoline ring systems (80JA3294,5274). In this work, the diene portion was initially masked as a 2-substituted 2,5-dihydrothiophene 1,1-dioxide. Thus, reaction of the acid chloride (312) with 3,4,5,6-tetrahydropyridine (311) afforded the masked enamido diene (313), which was converted to the enamido diene (314) upon brief refluxing in xylene. Thermolysis of (314) afforded the hydrolulolidine (315) in 45-55% yield. Additionally, (313) could be transformed to (315) directly by passage of a 1% solution in toluene through a vertical tube (600 °C oven temperature) (Scheme 67). The method was used to prepare a known precursor to aspidospermine. 

A [5 - 2 + 2 + 1] fragmentation followed by cyclization forming a new five-membered ring was observed by FVP studies of 2-propenyl-l,3-dithiolan 1,1-dioxide (79) (95H1967). The reaction mixture consists of four products thiophene (26%), 2,5-dihydrothiophene (80,34%), 4-methyl-2-propenyI-4//-l,3-dithiine (20%), and 2,6-dimethyl-2//,6//-l,5-dithiocine (20%). The last two compounds are formed by [4 + 2] or [4 + 4] dimerization of the intermediate 2-butenethial. Formation of 80 involves a 1,5-H shift of the as-butenethial, followed by cyclization. 

Dihydrothiophene-1,1 -dioxide (2-sulfolene) (131) underwent a photochemical [2+2] cycloaddition with maleic anhydride to yield cycloadduct 132 which contained a m-fused cyclobutane (Scheme 36).83 Simple reactions of the anhydride function provided access to a wide range of novel bi- and tricyclic sulfones 133-135 containing the novel 2-thiabicyclo[3.2.0]heptane-2,2-dioxide ring system. 

In an unusual reaction, 3-(piperidinomethyl)-2,5-dihydrothiophene 1,1-dioxide was obtained when 2,5-bis(trimethyl-silybthiophene 1,1-dioxide was reacted with excess piperidine in an aprotic solvent (Equation 59) <2000EJ03139>. 

Dihydrothiophene 1,1-dioxide in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) reacts with CO2 to give the carboxylic acid (Equation 69), which is a stable precursor to l,3-butadiene-2-carboxylic acid <2003SC3643>. The reaction proceeds through initial deprotonation at the 2a-position the resonance-stabilized carbanion thus generated reacts with CO2 to form the carboxylate. Abstraction of a proton from the 3-position by another molecule of the base generates a dianion, which isomerizes to the stable dianion as shown in Scheme 39. Final protonation produces 3-sulfolene-3-carboxylic acid. 

Reaction of 1,6-diynes 414 and 415 with Pdl2, CO, and O2 in methanol followed by treatment with Et3N affords hi- and terthiophenes 416 and 417, respectively <1999T485>. 2,5-Dihydrothiophene 1,1-dioxide 419 is synthesized by Ru-catalyzed hydrative cyclization of diyne 418 (Equation 12) <20050L2097>. 

The solvent-dependence of cheletropic reactions has also been investigated [158aj. The thermolysis of 3-methyl-2,5-dihydrothiophene-l,1-dioxide appears to involve a concerted fission of the two (T-bonds. This is in accordance with the very small solvent effect on rate observed in six solvents of different polarity [158a]. 

The reaction of an ethanol solution of stoichiometric amounts 3-oxo-2,3-dihydrothiophene 1,1-dioxide 646 with 1,2-ethanedithiol in the presence of pyridine provided 1,3-dithiolane 647 in 93% yield. The same reaction performed with 2 equiv of 1,2-ethanedithiol and PTSA as a catalyst afforded the bis-l,3-dithiolane 648 in 93% yield (Equations 89 and 90) <1996TL119, 1999J(P1)3085>. 

There are other kinds of cycloadditions, too. The [4 + 1] cycloaddition, a cheletropic reaction, usually goes in the retro direction for entropic reasons. 3-Sulfolene (butadiene sulfone, 2,5-dihydrothiophene 1,1-dioxide) undergoes a [4 + 1] retro-cycloaddition to generate S02 and 1,3-butadiene, which can undergo a Diels-Alder reaction with a dienophile. It is much more convenient to... 

Five membered ring sulfones (thiolene-1, 1-dioxides, sulfolenes or dihydrothiophene-1, 1-dioxides) can be obtained by peracid oxidation of tetrahydrothiophene. The extrusion of sulfure dioxide from dihydrothiophene-1,1 dioxides or sulfolenes like (178) has been much studied as it provides a synthetic route to dienes, e.g. butadiene (152) (Scheme 70). The reverse reaction provides a method of synthesis of sulfolene (178) from butadiene (152) and sulfur dioxide. Thiolene dioxides or sulfolenes can be generally prepared by addition of sulfur dioxide to conjugated dienes for example, 1,4-dimethylbutadiene (179) in the presence of sulfure dioxide, triethylamine and formic acid affords 2,5-dimethylsulfolene (180) (Scheme 71). 

---