Pyrolysis of tricyclic cyclobutane-fused sulfolanes as a route to cis-1,2-divinyl compounds and their Cope-derived products

Abstract

Functionalisation of the double bond of 3-thiabicyclo[3.2.0]hept-6-ene 3, readily formed by hydrolysis of the [2ϩ2] cycloadduct 1 of 3-sulfolene and maleic anhydride followed by oxidative bis-decarboxylation, gives tricyclic sulfones 5-7 and 9 with the bicyclo[3.3.0.0 2,4 ] skeleton. FVP of 3 results in stereospecific extrusion of SO 2 to give Z-hexa-1,3,5-triene which undergoes electrocylisation to give cyclohexa-1,3-diene while reaction of 3 with LiAlH 4 results in non-stereospecific extrusion to give Z-and E-hexa-1,3,5-triene. Upon FVP the tricyclic sulfones 5-7 and 9 lose SO 2 to give 7-membered ring products 16-19 by Cope rearrangement of the initially formed cis-1,2-divinyl intermediates 15. The 1,3-dipolar cycloaddition of nitrile oxides and a nitrone to the double bond of 3 gives tricyclic sulfones with the tricyclo[5.3.0.0 2,6 ] skeleton and a wider variety of these can be prepared by conventional reactions of 1. Upon FVP these lose SO 2 to give stable cis-1,2-divinyl compounds 23, 24, 37-40 and 41-44. The Diels-Alder adducts 48 and 49 have been prepared from 3 and these behave differently upon FVP, losing SO 2 and butadiene to give tetrasubstituted benzenes, in the latter case by way of an unexpected tetracyclic intermediate.Thermal extrusion of SO 2 from cyclic compounds has been widely used as a synthetic method and often allows access to products which would be difficult to obtain by other methods. 1 The pyrolysis of functionalised sulfolenes and sulfolanes is of particular importance and has found numerous applications. 2 Although there have been a few studies on cyclopropane-fused sulfolanes and their heterocyclic analogues, there were no examples of the corresponding method being applied to cyclobutane-fused sulfolanes prior to our work in the area. The general approach, summarised in Scheme 1, may be used to access a wide range of cis-1,2-divinyl compounds and, depending upon the ring size involved, the products derived from their Cope rearrangement. We now present full details of the synthesis of cyclobutane-fused sulfolanes with an additional 3-, 5-or 6-membered fused ring and their reactivity under flash vacuum pyrolysis (FVP) conditions. 3

Syntheses ofgem-Dihalocyclopropanes and Their Use in Organic Synthesis

“…Thermal rearrangements of strained bicyclic systems are particularly facile reactions. In fact, as was mentioned in section III, often isolation of the addition products from the reaction of dihalocarbene with cyclic, less-than-six-membered alkenes is not possible because of their rapid isomerization. ,, Some recent examples of thermal reactions of gem -dihalocyclopropanes 376 are given below (eqs 98, 99, and 100 226 ).

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Ethyl Nosyloxycarbamate: A Chameleonic Aminating Agent

“…In a similar manner, by using NsONHCO 2 Et in a two-phase (H 2 O/CH 2 Cl 2 ) system in the presence of sodium bicarbonate and BnEt 3 N + Cl -, tricyclic sulfones (Scheme 9) [32], 3,6,7-triazatricyclo[3.3.0.0. 2,4 ]octanes (Scheme 10) [33], and [60]fullero aziridines (Scheme 11) [34,35] were prepared.…”

Conformation and hydrogen bonding for the bicyclic compound 3-thiabicyclo[3.2.0]heptane-6,7-dicarboxylic acid 3,3-dioxide

“…A few years later the anhydride product, (I), known as the Bloomfield adduct, was patented by Monsanto as a chemical regulator of plant growth or development (Bloomfield, 1975). The various adducts formed by the addi-tion of an alkene to 3-sulfolene have found considerable use in synthesis (Aitken et al, 1999). The structure of (I) was determined at BP Research Centre, Sunbury-on-Thames, in 1982 by Smith (2003;see also Cadogan et al, 1982) and the exo configuration was established by single-crystal X-ray diffraction; unfortunately, the crystallographic data were never published and are no longer available.…”