PHOTOCHROMISM OF FULGIDES AND STEREOELECTRONIC FACTORS - SYNTHESIS OF5-DIMETHYLFURYL)ETHYLIDENE]TETRAHYDROFURAN-2-ONE-4 AND -DIMETHYLFURYL)ETHYLIDENE]TETRAHYDROFURAN-2-ONE-4A AND INOSTYRYL)BENZYLIDENE]TETRAHYDROFURAN-2,5-DIONE-10

In the search for fulgides with potential semiconductor laser compatib ility, -dimethyl-3-furyl)ethylidene]tetrahydrofuran-2-one (4), along w ith its regioisomer 4a, have been synthesized from the corresponding f ulgide 6 containing a succinic anhydride ring by reaction with malonon itrile in the presence of diethylamine. Upon irradiation with a uv lig ht at lambda(max) 350 nm, a mixture of 4 and 4a revealed a considerabl y enhanced bathochromic shift to the visible region, lambda(max) 605 n m as compared with the starting fulgide 6 which, upon analogous uv irr adiation, absorbed at lambda(max) 515 nm. In the search for semiconduc tor-laser-compatible fulgides with increased efficiency for the revers e bleaching reaction, another fulgide laminostyryl)benzylidene]tetrahy drofuran-2,5-dione (10) was synthesized in seven steps starting from 2 -bromo-m-xylene. However, 10 failed to undergo electrocyclic ring-clos ure upon irradiation with a uv light at lambda(max) 350 nm. The analog ous fulgide 8, which contains an isopropylidene functionality in place of the adamantyl group of 10, was resynthesized for comparison, and s howed two absorption maxima, one at 545 nm and the other at 620 nm. Th e missing physico-chemical data for 8 have also been provided.