Cycloaddition Behavior of 1,2‐Thiaphospholes: Reactions with Diazocumulenes and with Cyclopentadiene

Abstract

1,2-Thiaphospholes 3a,b react with (1-diazo-2-oxoalkyl)silanes 1a−c to form [1,2] ,2]thiaphosphole systems 4 with cis-anti-cis configuration of the tricyclic framework. They are accompanied by small amounts of compounds 5 that are presumably the cis-syn-cis isomers of 4, and 6-alkylidene-1-phospha-2-thiabicyclo[3.1.0]hex-3-enes 6. It is likely that these reactions proceed by [3+2] cycloaddition of diazocumulenes, which coexist with diazo compounds as minor equilibrium components, at the P=C bond of the heterophospholes, followed by N 2 elimination and formation of short-lived 2-alkylidene-

Cycloaddition reactions of heterophospholes

“…The latter undergoes subsequently successive ring expansion and further [4 + 2] cycloaddition either with dicyclopentadiene to form 22 or with cyclopentadiene to produce 23. The structure of 22 was confirmed by X-ray crystal studies [53] (Scheme 9).…”

“…In the case of 62 (R 3 Si = iPr 3 Si), the bicyclic alkylidenephosphi-SCHEME 21 ranes 72 were also isolated in low yields (4-8%). The structure of 70 (R 1 = tBu, R 3 Si = iPr 3 Si, Ar = Ph) was confirmed by X-ray crystal studies [53]. In the reaction of 62 (R 1 = tBu, R 3 Si = iPr 3 Si) with 19 (Ar = Ph), trace amount of 71 was also isolated [53] (Scheme 21).…”

“…1,2-Thiaphosphole, acting as heterodiene, shows interesting reactivity towards cyclopentadiene [53] and cyclooctyne [54]. With cyclopentadiene no reaction occurs at 20-80…”

“…Recently [3 + 2] cycloadditions of (1-diazo-2-oxoalkyl)silanes have been investigated with 2H-1,2,3-diazaphospholes [81], 3H-1,2,3,4-triazaphospholes [82], and 1,2-thiaphospholes [53]. The silanes 61 are in equilibrium with minor amounts of diazocumulenes 62 which are much more reactive 1,3-dipoles than the former [83].…”

Unexpected Thermal Reactivity of Phosphirano‐[1,2]thiaphosphole P–W(CO)5 Complexes

“…A versatile approach to [a]-fused phosphiranes is provided by the cyclopropanation of the P=C bond of heterophospholes with diazo compounds through a [3+2] cycloaddition/ring-contraction sequence. [10] As 3,5-diaryl-1,2-thiaphospholes are readily available [11] and the P=C bond of 1,2-thiaphospholes is an excellent cycloaddition partner, [12][13][14] we followed this route to synthesize a 6,6-diphenyl-2-thia-1-phosphabicyclo[3.1.0]hex-3-ene using diazodiphenylmethane as the cyclopropanation reagent. [15] We found that the thermal stabilities of both the phosphirane and its W(CO) 5 and Fe(CO) 4 complexes are only moderate, and that the effect of elevated temperatures is different for the free phosphirane and its metal complexes.…”