Jaswant Rai Mahajan

Synthesis of (±)-Recifeiolide and Its Homologs via Acetylenic Lactones

Abstract The title compounds (7c,d) have been prepared by the Z to E isomerization (NaNC2, HNO3) of the corresponding Z-lactones (6c,d), which are stereoselectively available (H2, Lindlar cat.) from the acetylenic lactones 4a-d, prepared earlier from cycloalkanones.

Synthesis of medium ring and macrocyclic acetylenic lactones by the ring expansion of oxabicycloalkenones

Medium to macrocyclic acetylenic lactones 15a-e 6-decyn-9-olide (15a), 7-undecyn-10-olide (15b), 8-dodecyn-11-olide (15c), 12-hexadecyn-15-olide (15d), and 5-decyn-9-olide (15e) were prepared from oxabicycloalkenones 7a-d and 2, respectively, by the ring expansion of their tosylhydrazones 16a-e, carried out by reaction with N-bromosuccinimide, under strictly controlled conditions. Complete hydrogenation (Pd-C, H2) of the triple bond gave the racemic saturated lactones: 9-decanolide (phoracantholide I, 6, from 15a and 15e), 10-undecanolide, 11-dodecanolide (dihydrorecifeiolide), and 15-hexadecanolide. The attempts at the conversion of dihydropyrones 7a,d into the respective acetylenic lactones 15a,d, via chlorohydrins 8a,d and/or chloroketolactones 9a,d, were only partially successful.

Synthesis of acyclic insect pheromones from cycloalkanones via acetylenic lactones

Figure 1 describes a general method for the preparation of insect pheromones. Several members of the title compounds, along with their geometric and/or positional isomers, have been prepared from Z-lactones 2a-d, which are easily available from the corresponding acetylenic lactones 1a-d, prepared earlier from cycloalkanones. The Z to E isomerization of alkenyl acetates 6a-d to 8a-d was carried out both by a catalytic technique (NaNO2, HNO3, D) and the chemical inversion procedure (NBS, TFA; NaI, DMF, D). (E)-6-Decenyl alcohol (7b) was also prepared from the acetylenic ester 15b by the trans reduction with LiAlH4 in refluxing diglyme. decyl acetate (18) and hexadecyl acetate (19), pheromone components of the turnip moth (Agrotis segetum) and the male butterfly Lycorea ceres ceres, respectively, were obtained by the catalytic hydrogenation (Pd, H2) of the corresponding Z-alkenyl acetates.

A new synthesis of medium ring and macrocyclic acetylenic lactones from oxabicycloalkenones via their tosylhydrazones

Tosylhydrazones 4a–d of vinylogous lactones 1a–d on treatment with N-bromosuccinimide, under strictly controlled conditions, give the title acetylenic compounds 5a–d in 65–90% yield.