A Ring-Enlargement Reaction Yielding 1,2,5-Benzothiadiazonin-6-one 1,1-Dioxides

At room temperature or under reflux in MeCN, 3-amino-2H-azirines 2 and 3,4-dihydro-2H-1,2-benzothiazin-3-one 1,1-dioxide (4) give 1,2,5-benzothiadiazonin-6-one 1.1-dioxides 5 in fair-to-good yield (Scheme 2). The structure of this novel type of heterocyclic compounds has been established by X-ray crystallography of 5a (Fig.). A ring expansion via a zwitterionic intermediate of type A' is proposed as the reaction mechanism of the formation of 5

Carbonyliron Complexes of Allenic Acids, Esters, Amides, and Imides

On irradiation in the presence of Fe(CO)5, the allenic amides and imides showed a similar course of complexation to that of esters and lactones, respectively, e.g. the amides of type 10 led to diiron complexes of type 11 (Scheme 3 ), whereas the imide 12 yielded a mixture of a dinuclear and two mononuclear complexes (13-15, Scheme 4). The racemic ester 6 also gave mononuclear (7a, 7b, and 9) and dinuclear complexes (8a and 8b; Scheme 2). In case of the allenic acid 4, only complexation of type 5 was observed (Scheme 1)

Synthesis and Structure of Carbonyliron Complexes of Allenecarboxylates and Allenic Lactones

On irradiation in the presence of Fe(CO)5, the allenecarboxylates 1 afforded binuclear carbonyliron complexes 6 (Scheme 3), whereas the allenic lactone 7 under similar conditions gave a mixture of one binuclear and two mononuclear carbonyliron complexes (9, 8, and 10; Scheme 4). The structure of the complexes has been elucidated by X-ray crystallography. The structure of the binuclear complex 9 corresponds to that of 6, while 8 has been shown to be a 1,3-butadiene(tricarbonyl)iron complex. The unique structure of 10 represents a new type of allenic complex. A stepwise formation of the complexes via intermediate allene(tetracarbony1)iron complexes of type 11 and 13 is suggested. Treatment of the binuclear complex 6h with FeCI3 led to the formation of the free ligand and a mixture of mononuclear complexes 13 and 14 (Scheme 5). On heating, the 1,3-diene complex 8 yielded the free ligand 15, the product of a (1,3) H shift in the allene 7; the complex 10 on the other hand liberates 7 on treatment with ethylenetetracarbonitrile (TCNE) (Scheme 6)

A Novel Photochemical Rearrangement of Allenic Esters

The alkyl allenic esters (1a-c) on irradiation are found to afford the cyclobutenones (2a-c) while the phenyl ester (1e) affords the photo-Fries product (4)