Sulphenes aminals

The presence of a second tertiary amine group can result in further complications owing to competition with the neighbouring enamine function for the electrophilic sulphene204 (Scheme 88). Aromatic sulphonyl chlorides cannot form sulphenes and hence give the acyclic sulphone205-207 (Scheme 89). 

Solid samples of S2I2 and SOI2 have been prepared by the reaction74 between HI and S2C12 and SOCl2 respectively, in Freon(II) at —78 °C. The dark brown solids are only stable below — 30 °C and in the absence of water. Nucleophilic substitution at the carbonyl carbon atom in C1C(0)SC1 has been shown75 to be more rapid than at the carbon atom in FC(0)SC1. The S—Cl bond of both sulphenic acid chlorides shows no noticeable difference in reactivity. Although amines react with C1C(0)SC1 at the carbonyl carbon, FC(0)SC1 is attacked at the S—Cl bond. 

Sulphonyl halides, most commonly the chlorides, may also be converted into sulphonic acids via a route involving sulphenes. Normally, sulphene is formed by reaction of a sulphonyl chloride, which possesses an a-hydrogen atom, with a tertiary amine as shown in equation 62. There are, however, many other routes by which sulphenes may be formed and these have been reviewed previously305. The intermediate sulphene then reacts with water to give the sulphonic acid. If D20 is used, then a deuterated sulphonic acid is produced306-310, as indicated by equation 63. 

Reaction of sulphonyl halides, that contain an a-hydrogen atom, with tertiary amine bases, under anhydrous conditions, usually occurs via a reactive sulphene intermediate. 

The reaction of a sulphonyl chloride with amines to produce a sulphonamide also occurs in the presence of a base305,307,482,483. In this case, it is well established that the reaction proceeds via a sulphene intermediate, as shown in equation 117. Using this method for the preparation, some novel sulphonamides may be obtained. Thus, the reaction of sulphene with phthalimide give iV-methylsulphonylphthalimide484,485, as shown in equation 118. Reaction of sulphene with pyridine leads to a novel cyclic... 

Sulphenes, generated in situ from alkanesulphonyl halides and tertiary amines (equation 11), were the subject of much attention during the 1960s34, mainly concerning their addition to C=C bonds. Surprisingly, the addition of these ylids to carbonyl bonds... 

Sulphenes, generated by reaction with tertiary amines (see Sections II.A.2 and II.B.2), react with SchifFs bases to give /7-sultams258,259. In all cases so far, Z-sultams predominate in the product mixture so that Hirotoka and Kobayashi have suggested a concerted [tc2s + 7t2s] mechanism for the reaction (equation 205)259. 

Kinetic studies in the benzothiazole series include examination of the base-catalysed reaction between 2-fluoro-6-nitrobenzothiazole and aliphatic amines, " investigation of the mechanism of formation of sulphenic acid amides... 

Classically, imines have been obtained via derivatisation of carbonyl compounds although problems exist in the use of unreactive carbonyl compounds and/or volatile imines. This transformation has nevertheless been achieved in excellent yields in the absence of solvent merely by treating carbonyl compounds dispersed on alumina with amines that have been similarly dispersed on alumina, Trimethylsily1 trifluoromethanesulphonate has been found to catalyse formation of imines from carbonyl compounds and 1,N-bis-(trimethysilyl )amines, these reactions also proceeding in excellent yield.The same research group also discovered that sulphen-imines could be isolated from reactions between tJ-bis (trimethyl-... 

Sulphonyl Halides and Sulphenes.—It is becoming clear that reactions of alkanesulphonyl chlorides in the presence of a tertiary amine are likely to give poor yields of simple sulphonation products, due to the formation of sulphenes (RCHaSOgCl RCH=SOa) and artefacts resulting from them. Electron-withdrawing groups in the substituent facilitate sulphene... 

Paquette et alf have shown that the well-known reaction of sulphenes with vinyl amines to form thietan dioxides is amenable to asymmetric induction. The reaction of the parent sulphene with electronegatively substituted carbonyl compounds can follow two courses (see Scheme 1),... 

Oxathietan 1,1-dioxide (130) reacts with alcohols to give (2-fluorosulphonyl)-carboxylic esters, and with BFj and EtjN to give fluorosulphonyl(trifluoro-methyl)keten. The latter reaction is more efficient if the ring is first opened with KF and HF. Chloral cyclo-adds to sulphenes to give yff-sultones. 4-Tri-chloromethyl-l,2-oxathietan 2,2-dioxide reacts with primary and secondary amines to give y5-hydroxy-sulphonamides. ... 

Sulphonylamines and Sulphurtri-imides.—As analogues of sulphenes, sulphonyl-amines were generated from chlorosulphonylamines and triethylamine to give, e.g., (38) as an intermediate, which could be added to a diazoalkane to yield a... 

The synthesis and properties of optically active thiet 1,1-dioxides have been reviewed. The generation of sulphenes from p-nitrophenyl sulpho-nates is claimed to have advantages in the preparation of 3-amino-4-arylthiet 1,1-dioxides from acetylenic amines, principally in the avcndance of the presence of triethylamine hydrochloride, which is believed to cause isomerization of the thiet derivative. Several other thiet dioxides have been obtained by reaction of a sulphene with an acetylenic amine. - They are claimed to be anti-inflammatory agents. The formaticm of a thiet 1,1-dioxide from acetylenic sulphine (167) and an enamine has been noted previously. A number of substituted thiet dioxides have been prepared by addition of sulphene to enamines followed by a Cope elimination of the amine. These compounds were tested for analgesic activity but none was found. Thiet 1,1-dioxide (123) is obtained from... 

Thioamide vinylogues (100) have been reported to yield Diels-Alder adducts on treatment with substituted alkenes and sulphenes/ In the former case, the heterocyclic compounds (107) and/or (108) were produced, depending on the substituents. In the latter case, the unsubstituted sulphene afforded merely (109), whereas solely the de-aminated products (110) were formed in reactions with benzylsulphene. 3-Alkylthio-l-aryl-3-arylamino-2-propene-l-thiones (41) have been converted into 3-arylamino-1,2-oxazoles, 3-arylaminopyrazoles, and the quinoline derivatives (111) by treatment with hydroxylamine, hydrazine, and sulphuric acid, respectively. " The formation of 2-imino-2H-thiopyrans by spontaneous ring-closure of -mercaptovinyl-acrylonitriles (112) has been reported recently. ... 

King and his co-workers have observed that alkanesulphonyl chlorides with more than one a-hydrogen atom react with deuterium oxide in the presence of sterically unhindered tertiary amines to form alkanesulphonates having more than one of the a-hydrogen atoms exchanged. This observation was rationalized in terms of a reaction sequence involving intermediate sulphenes and zwitterions (Scheme 9). Kinetic studies in connection with... 

Whereas sulphene itself reacts with vinyl amines to afford cyclic adducts [e.g. (102) ], benzoylsulphene sulphonates the vinyl amine in good yield to afford (103). A common type of zwitterionic intermediate probably is... 

Ylides of Sulphur, Selenium, Tellurium, and Related Structures 359 was proposed that sulphene formation was involved in each reaction, with the triphenylphosphine adding to the sulphene and displacing SO2 to afford the phosphonium ylide, which was protonated by the conjugate acid of the amine. Sulphenes have been reported to react with tropone to afford an adduct which rearranged on heating to an o-hydroxystyrene (lOQ. ... 

Omeprazole becomes completely ionised and thus trapped in secretory channels of the parietal cells due to an acid-catalysed rearrangement which converts it into a quaternary amine. The mechanism of the structural rearrangement is not known exactly. It seems likely that it is the sulphenic acid (Fig. 12.29) intermediate that reacts with the H K ATPase and rather than the sulphenamide (Fig. 12.29), which is a more stable end product of the rearrangement. ... 

---