Nandakumar S. Rao

Thionin oxide as a Possible Intermediate on Periodate Oxidation of 9-Thiabicyclo[6.1.0]nona-2,4,6-triene

Abstract 9-Thiabicyclo[6.1.0]nona-2,4,6-triene was oxidized at −15 to −20°C with sodium periodate in a methanol-water medium. The major isolated product was established as cis 3a,7a-dihydrobenzo[b]thiophene- cis -1-oxide, which is best explained as arising from intramolecular cycloaddition of a thionin oxide intermediate.

COMPARATIVE STUDIES ON SYNTHESIS AND PROPERTIES OF PHOSPHORUS AND SULFUR HETEROCYCLES: THE HETERONIN OXIDE SYSTEM

Abstract Phosphonin oxides are the first recognizable product on reaction of 9-phosphabicyclo[6.1.0]nona-2,4,6-trienes with peroxides at −15°C. These compounds (R = C6H5 or t-C4H9) are stable below −15°C, but undergo intramolecular cycloaddition to give trans-3a,7a-dihydrophosphindoles on warming to room temperature. The reaction applied to the sulfur counterpart of the phosphine gave only the 9-thiabicyclo[4.2.1]nonatriene system, but oxidation with sodium periodate at −15°C gave a 34% yield of a product identified conclusively as cis-3a,7a-dihydrobenzo[b]thiophene oxide, which must have arisen from a thionin oxide. This is the first evidence for the formation of a noncyclic thionin derivative.

O-SILYLATION OF SOME UNSATURATED CYCLIC PHOSPHINE OXIDES

Abstract The phosphoryl oxygen of 1.6-dihydrophosphinine oxides is silylated rapidly at room temperature by bis(trimethylsilyl)trifluoroacetamide; the product loses a ring proton to establish the resonance stabilized γ5-phosphinine ring system. Similar events take place with a 3-keto derivative of a tetrahydrophosphinine oxide, which also undergoes silylation of the keto oxygen. 1,4-Dihydro-lazaphosphinine are silylated to give 1,4-aza-γ5-phosphinines; their dibenzo derivatives (5,10-dihydrophenophosphazine oxides) require more forcing conditions (triethylsilyl bromide at 100°C) for phosphoryl silylation. These conditions are also effective for silylation of a 3-phospholene oxide.

Construction of the 17-Thiasteroid Ring System by the Diene-Sulfur Dioxide Cycloaddition Reaction

Abstract We recently showed2 that the steroid ring system can be constructed with a phosphorus atom replacing a carbon in the D-ring by the cycloaddition of a phosphorus (III) halide with a diene that is a vinyl dihydrophenanthrene derivative, such as (1). The phosphine oxide (3) resulting from the hydrolysis of the initial cycloadduct (2) has some resemblance to the hormone equilenin, which also has rings A and B in naphthalene form.