Falmai Binns

Thermal electrocyclic ring-opening of cyclobutenes: stereoselective routes to functionalised conjugated (Z,E)- and (E,E)-2,4-dienals

Abstract The cyclobutenecarbaldehyde 12 undergoes thermal electrocyclic ring-opening at low temperature, producing the (2Z,4E)-hexadienal 13 exclusively. By contrast, unsymmetrical derivatives of cis-3-cyclobutene-1,2-dicarboxylic acid undergo ring-opening at 80–110°C with low levels of stereoselectivity, which vary according to the balance of the electronic and, to a lesser extent, the steric nature of the substituents located on the rehybridising carbon atoms.

Studies leading to the large scale synthesis of polyesters using enzymes

The ability of immobilised Candida antarctica lipase to catalyse the condensation of diols and diacids was studied. The range of acids investigated (in condensations with butane-1,4-diol) included adipic, maleic, fumaric, itaconic, (E)-hex-3-enedioic and acetylenedicarboxylic acids, while the diols studied, in condensations with adipic acid, encompassed ethane-, propane-, butane-, pentane- and hexane-diols as well as (Z)-but-2-ene-1,4-diol and but-2-yne-1,4-diol. The oligomerization of hexane-1,6-diol and adipic acid was most facile and was chosen for scale-up. A mechanism for the polycondensation process is proposed.

The preparation and electrocyclic ring-opening of cyclobutenes: Stereocontrolled approaches to substituted conjugated dienes and trienes

Abstract Thermal electrocyclic ring-opening of 4-alkyl-2-cyclobutene-1-carbaldehydes occurs at low temperature to give (2 Z ,4 E )-alkadienals exclusively, and the process is exploited in transforming cis -3-cyclobutene-1,2-dimethanol 1 into a variety of naturally occurring 1,3,5-alkatrienes and 2,4-decadienoates. Desymmetrisation of 1 with Pseudomonas fluorescens lipase gives access to both enantiomers of 3-oxabicyclo[3.2.0]hept-6-en-2-one 4 , for use in stereocontrolled routes to 6-oxygenated (2 Z ,4 E )-alkadienals.

An unsuccessful approach to the framework of the antimalarial, arteether

Abstract The hexahydrobenzopyran 7a , prepared using the new acetone anion equivalent 17 , reacted with singlet oxygen to produce mixtures containing the dioxetane 6 , but in situ treatment with acid failed to generate detectable amounts of 4 , an analogue of the antimalarial arteether 3 .

Isolation, synthesis and reactivity of a key macrobislactone; 1,4,7-trioxacyclotridecane-8-13-dione

Abstract Macrobislactone 1, 1,4,7-trioxa-cyclotridecane-8-13-dione, believed to be the cause of the fogging of car windscreens by an oily film, has been formally synthesised from diethylene glycol and adipic acid and its content in commercial polyester formulations has been estimated. Study of its ring-opening potential towards both anionic and enzymatic reagents reveal surprizing stability in polyester formulations, coupled with anomalous high susceptibility in the pure state to the lipase Candida antarctica, immobilized as Novozyme™. Assay of macrobislactone 1 in a range of polyesters suggest that there is significantly more of this key lactone present than trends would predict Reasons for this behaviour are advanced following modelling studies and from thermodynamic considerations.