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Cycloaddition Behavior of 1,2‐Thiaphospholes: Reactions with Diazocumulenes and with Cyclopentadiene
Author(s) -
Kerth Jochen,
Jikyo Tamaki,
Maas Gerhard
Publication year - 2003
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200300004
Subject(s) - cyclopentadiene , chemistry , cycloaddition , dimer , medicinal chemistry , silanes , bicyclic molecule , diazo , stereochemistry , organic chemistry , catalysis , silane
1,2‐Thiaphospholes 3a , b react with (1‐diazo‐2‐oxoalkyl)silanes 1a − c to form [1,2]thiaphospholo[2′,3′:3,4][1,3]diphospholo[1,5‐ b ][1,2]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‐1,2(λ 5 )thiaphospholes. The latter can either add to excess thiaphosphole to form the tricyclic products or undergo electrocyclization to form bicyclic alkylidenephosphiranes. Thiaphosphole 3a does not seem to react directly with cyclopentadiene in a [4+2] or [2+4] cycloaddition. Reaction with excess cyclopentadiene at 120 °C yields the polycyclic compounds 15 and 16 , which are likely to arise from a Diels−Alder reaction of 3a , reacting as a heterodiene, with the cyclopentadiene dimer. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)