Sulfamide, ring closures with

Ring closure with sulfamides 2H-1,2,6-Thiadiazine 1,1-dioxides... 

Bis(phosphine imines), ring closures with - 31, 424 N,N -Bis(phosphoranylidene)-sulfamides... 

One straightforward route to the aziridine ring system is available through the ring closure of vicinal amino alcohols, an approach which has been used to prepare vinyl N-H aziridines. Thus, 4-amino-l-phenylhex-5-en-3-ol (111) was treated with sulfuryl chloride to provide the sulfamidate 112, which underwent clean thermolysis at 70 °C to form the vinyl aziridine 113 in 97% overall yield <02T5979>. 

The chemistry of 1,2,4,6-thiatriazines and related compounds began with the synthesis of l,3,5-tris(4-methoxyphenyl)-124,2,4,6-thiatriazine in 1904.4 The saturated ring system, obtained by ring-closure reaction of sulfamides with formaldehyde, was first described in 1946.5 The first practicable synthesis of l/.4,2,4,6-thiatriazines and their structural elucidation was reported in the early 1950s.6-8 The second period of investigations into the synthesis of l/.4,2,4,6-thiatriazines began when methods for the synthesis of halo-substituted thiatriazines were developed in 1972.9-10... 

The 5,6-dihydro-477-l,2,6-thiadiazine 1,1,2-trioxides (162) described in Section 6.16.9.2.3.1 are susceptible to nucleophilic attack at sulfur, which promotes heterolytic cleavage of the heterocyclic ring and formation of )S-hydroxyaminosulfamic acid derivatives (163) as outlined in Scheme 15 <90LA775>. However, with a primary amine as the attacking nucleophile the sulfamides (163) so formed undergo base-catalysed ring closure to the 4,5-dihydropyrazoles (164) in yields of 72-90%. 

Amino-17f-2,l,3-benzothiadiazine 2,2-dioxide (217) is readily obtained, although in moderate yield, by ring-closure of A-(2-cyanophenyl)sulfamide (216) in aqueous sodium hydroxide (84AP(317)777>. The cyclization is also successful with the corresponding Af-(3-cyano-5,6,7,8-tetra-hydrobenzothien-2-yl)sulfamide, but fails with 7V -substituted Af-(2-cyanophenyl)sulfamides... 

Thiadiazine 1,1-dioxides are also accessible by condensation of sulfamides with ethyl 3,3-diethoxypropionate in trifluoroacetic acid (Section 6.16.9.1.1), and by acid catalysed ring-closure of A-acetoacetylsulfamides (Section 6.16.9.1.2). Amino derivatives are obtained by acid-catalysed ring closure of A-(2,2-dicyanoethylidene)-sulfamide (Section 6.16.9.1.2) and by ring-contraction of 4i/-l,2,4,6-thiatriazine 1,1-dioxides in the presence of malononitrile or ethyl cyanoacetate anions (Section 6.16.10). 

The less common l//-2,l,3-benzothiadiazine 2,2-dioxides have been prepared by cyclization of 2-aminobenzylamines with sulfamide (Section 6.16.9.2.3.1) and their 4-amino derivatives, by ring closure of A -(2-cyanophenyl)sulfamides with aqueous sodium hydroxide (Section 6.16.9.1.2). The equally uncommon 2,1,3-benzothiadiazine 1-oxides are available in almost quantitative yields, by addition of arylsulfinylamines with benzylideneanilines (Section 6.16.9.2.2.2). 

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