Arylsulphonyl azetidine compounds, their preparation and their use as intermediates

Azetidine compounds of the general formula I (I) wherein Ar represents a para-tolyl group and X represents a hydrogen atom, a carboxyl group or a hydroxymethyl group; their preparation from pentaerythritol via compounds of formula +TR or two hydroxyl groups and Z represents Hal or OH, together with their use as intermediates in the preparation of 3-carboxyazetidine; also the compounds of formula (VI) wherein R1 and R2 both represent hydrogen, or together represent The compounds are intermediates for a known chemical hybridizing agent.