Ian G. Pitt

Photoisomerisation of bicyclo[4.2.0]octadienes to tricyclo[4.2.0.02,5] octenes : application to the synthesis of [n]ladderanes

Abstract A new approach for the extension of [n]ladderanes is described which involves formation of an end-fused bicyclo[4.2.0]octadiene and its photoisomerisation to the related tricyclo[4.2.0.02,5] octene as the ladderane extension step. The protocol is illustrated with the synthesis of [3]ladderane (9) from an unsubstituted cyclobutene and nor[5]ladderane (13) from an ester activated cyclobutene. The exo-stereochemistry of (13) is confirmed by reference to intermediate (23) for which a single crystal X-Ray structure analysis was obtained.

Dimethyl octamethyltricyclo[4.2.2.02,5]deca-3,7,9-triene-7,8-dicarboxylate (Cookson's diester) revisited: Cope rearrangement and epoxidation site selectivity

Dimethyl octamethyltricyclo[4.2.2.0 2,5 ]deca-3,7,9-triene-7,8-dicarboxylate (Cooksons diester) ( 8 ) is rearranged thermally via a double Cope reaction to its ring-degenerate isomer ( 14 ). The structure of diester ( 8 ) (indirectly) and the rearrangement product ( 14 ) (directly) are placed on an unequivocal base by X-Ray structure analysis. AMI semi-empirical calculations support the preferential formation of ( 8 ) from the reaction of DMAD with transient intermediate diene ( 7 ). Epoxidation studies (mCPBA) have been conducted and firm site selectivities determined. A correction is made to an earlier report on the epoxidation selectivity of ( 18 ).

Transfer technology I. An improved protocol for chemical synthesis.

Abstract A new protocol (Transfer Technology) is described in which stable molecules (Transfer Reagents) are employed as synthetic equivalents for synthons or highly reactive / unstable molecules in the preparation of substituted benzenes and other target molecules.

Transfer technology II. Preparation of transfer reagents for the site specific delivery of disubstituted cyclobutadienes and their use in the synthesis of hetero bridged propellanes.

Abstract Transfer reagents (11) and (18) are used as synthetic equivalents for disubstituted cyclobutadienes in a new protocol for the synthesis of the heteropropellanes (5), (6) and (16).

A New Reagent for the Generation of Tetramethylcyclobutadiene Under Thermal or Photochemical Conditions

Abstract A new, stable, easy to prepare synthetic equivalent for tetramethylcyclobutadiene is described. This reagent can be used under thermal or photochemical conditions and offers advantages over existing alternatives.

A new diene permitting evaluation of facial selectivity in Diels–Alder additions and preparation of a norbornadienone

The reaction of 5,6-dimethylene-1,4-dimethyl-2,3-diphenylnorborn-2-en-7-one (6) with dienophile, is used as a probe for π-facial selectivity in Diels–Alder reactions and is shown to proceed through norbornadien-7-ones, one of which exhibits moderate stability.

The synthesis of new linear and angular systems useful as rigid rods and spacers in the design of molecules

Various substituted norbornenes are subjected to metal-catalysed [2 + 2] cycloadditions to yield activated cyclobutenes which react further with quadricyclane to yield linear binadienes, or with cyclopentadiene to form angular binadienes; these binadienes are rigid alicyclic frameworks available to synthetic chemists for molecular design.

The generation and trapping of a novel Dewar furan

2,4,7-Trimethyl-7-aza-3-oxatricyclo[3.3.0.02,4]oct-1·(5)-ene-6,8-dione (7), a derivative of the rarely observed Dewar furan ring-system, has been prepared by Zn–TiCl4 debromination of dibromide (6) and trapped in in situ with furan.

A photochemical approach to methyl-substituted 5-oxabicyclo[2.1.0]pent-2-enes (Dewar furans)

U.v. irradiation of the N-methylsuccinimide-containing propellanes (12) and (13) yields the cyclopropenyl ketones (19) and (20) logicallly derived by the intermediacy of the Dewar furans (15) and (16).

Photodimers of isobenzofuran: a novel application of lanthanide induced shift spectroscopy to determine stereochemistry

In aceptone solution u.v. irradiation of isobenzofuran at –60 °C forms an [8 + 8] dimer shown by lanthanide induced shift spectroscopy to have the anti-stereochemistry; in ether solution an [8 + 8] dimer is obtained together with a skeletally modified dimmer, the structure of which is confirmed by synthesis.