Different thermal reactivity of a 1,2-thiaphospholo[a]phosphirane in free and metal carbonyl complexed formElectronic Supplementary Information (ESI) available: full experimental, spectroscopic and analytical data. See http://www.rsc.org/suppdata/cc/b3/b310256d/

Abstract

The W(CO)5 and Fe(CO)4 complexes of the bicyclic phosphirane 3,5,6,6-tetraphenyl-1-phospha-2-thiabicyclo[3.1.0]hex-3-ene undergo a thermal 2-phenylphosphirane --> dihydrophosphaisoindole ring expansion, while the free phosphirane suffers both a [2 + 1] cycloreversion and a fragmentation yielding a butadienyl sulfide.

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

“…[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.…”

“…[15] The uncomplexed phosphirane 1a undergoes a thermal fragmentation to yield a butadienyl sulfide (i.e., a tautomer of an alkenyl thione that is structurally analogous to 16 in Scheme 8), for which a phosphinidene cycloreversion, analogous to the one proposed above for the W(CO) 5 -complexed phosphiranes 10, has been suggested. The W(CO) 5 complexes 2, on the other hand, undergo a skeletal rearrangement (see Scheme 1) beginning with a homolytic cleavage of the phosphirane C-C bond, which is in contrast to the suggested P-C bond cleavage of 10 at elevated temperature.…”

“…In our earlier communication, [15] we reported that the 3,5,6,6-tetraphenyl-substituted phosphirano-thiaphosphole 1a smoothly forms a pentacarbonyltungsten-(P-W) complex 2a, which undergoes a skeletal rearrangement to the W(CO) 5 -complexed dihydroisophosphindole 3a at elevated temperature (Scheme 1). We have now found that the W(CO) 5 complex of the analogous 3-(4-anisyl)-substituted bicyclic phosphirane 1b can be observed in solution (δ P = -57.5 ppm) but cannot be isolated in pure form because it is readily transformed into dihydroisophosphindole 3b under the conditions of its formation from 1b (25°C, 24 h).…”

“…The products obtained differ significantly from the tricyclic thieno[3,2-a]isophosphindole derivatives 3 observed upon heating of the analogous 6,6-diphenyl-1,2-phosphirano-thiaphosphole complexes 2 (see Scheme 1). [15] For the spiro-connected complexes 10, heating at 80°C in toluene led to the thiaphosphirane complexes 11 [δ P = -6.4 (11a), -6.2 (11b), -6.9 (11c) ppm] in yields of up to 80 % (Scheme 6 and Table 1). Bicyclic dithiaphospholanes 12 were obtained as minor byproducts as a mixture of two stereoisomers (e.g., 12a: δ P = 54.3 and 53.1 ppm, 7:1 ratio; repeated chromatographic purification shifted this ratio to 10:1).…”

Methylene‐Azaphosphirane as a Reactive Intermediate

“…While the [1,3]-sigmatropic shift of vinylphosphiranes into phospholenes is experimentally ascertained, [45,46] there is scant precedent for this type of rearrangement with aromatics. [47] In addition, the [1,5]-sigmatropic phosphirane-phospholene rearrangement has also been observed experimentally, [43] but no precedents are known for this rearrangement with aromatics. Expectedly, 2-aminophosphindole 34 is the global minimum and can be formed directly from 33 via a hydrogen shift to nitrogen [48] with an exothermicity of 31.4 kcal mol À1 ; its bond lengths are in good agreement with those experimentally ascertained for compound 16 a in the crystal.…”