2.3.4.5- Tetrahydro-1 -benzoxepin

Benzoxepin, 2,3,4,5-tetrahydro-applications, 7, 590 bond fission, 7, 549 synthesis, 7, 577... 

A tandem palladium-catalysed ort/io-alkylation/intramolecular Heck reaction coupling sequence was used effectively to access in fair yields the tetrahydro 1-benzoxepines 67 from the iodoaryl precursor 66 and the appropriate alkyl bromide. The norbornene plays a relay role in the proposed reaction cycle <06JOC4937>... 

A new BF3-induced stereospecific rearrangement of the epoxy ethers 68 gave the enantiopure tetrahydro 2-benzoxepin-4-ols 69a, b in generally good yields <06JOC1537>. The enantiomerically enriched compounds 69c,d were also produced. 

Benzoannelation of the oxepane ring system leads to an increase in the barrier to ring inversion. Thus variable temperature NMR spectra on l,2,4,5-tetrahydro-3-benzoxepin (2) suggested that a chair conformation was preferred with a barrier to ring inversion of ca. 39.7 kJ mol"1. 

The predominant initial bond fission in 2,3,4,5-tetrahydro-l-benzoxepin (6) was again at the C—O bond with ring contraction steps occurring to yield five- or six-membered ring products (68OMS(l)403, 730MS(7)479>. 

Iodobenzyl propargyl ether 57 cyclizes with 7t-allylpalladium (Scheme 18) to form after trapping by a secondary amine tetrahydro-2-benzoxepines 58 in 70% yield. The piperidino derivative 58 (R2 = (CH2)5) undergoes Diels-Alder reaction with 4-phenyl-l,2,4-triazole-3,5-dione as dienophile to give a spiro derivative 59 in 44% yield <1996TL6565>. 

Several l-haloalkyl-l,3,4,5-tetrahydro-2-benzoxepins, e.g. (144), have been synthesized via the electrophilic cyclization of mixed acetals, e.g. (143). ... 

Difluoro-2,3,4,5-tetrahydro-2//-l-benzoxepine (8) and 2,2-difluoro-2,3,4,5-tetrahydro-2//-l-benzoxocin (10) have been prepared in low yield by oxidative ring expansion reaction of cyclic aromatic ketones 7 or 9 with Xep2 (Fig. 10.3). ... 

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