Systematic structural modifications in the photochemistry by .beta.,.gamma.-unsaturated ketones. I. Cyclic olefins

Abstract

The photochemical behavior of six 0,7-unsaturated ketones (5a-e, 19), whose double bond is incorporated into rings of four to eight members, has been studied under acetone sensitization and direct irradiation. In the triplet manifold, the four and five-membered rings undergo the oxadi-ir-methane (ODPM) rearrangement, but the larger rings do not. Only the four-membered compound (5a) shows a cleavage upon direct irradiation, but all of the others give cyclobutanols. The seven-and eight-membered compounds yield oxetanes, a reaction which is favored by high olefin electron density and the ability of the olefin to twist in the excited state. Several thermal rearrangements of the products to starting ketone and to one another have been noted.

Preparation of β-and γ-lactams via ring closures of unsaturated carbamoyl radicals derived from 1-carbamoyl-1-methylcyclohexa-2,5-dienes

“…Ammonia was obtained from BOC and used directly from the cylinder; drying and distillation had no perceptible effect on the yields. N-Benzyl-N-but-2-enylidineamine, 9 N-benzyl-N-but-2-enylamine, 9 benzylaminoacetonitrile, 19 prop-2-ynylbenzylamine, 20 1-methylcyclohexa-2,5-diene-1-carbonyl chloride (6), 10 2,2-dimethylbut-3-enoic acid, 21 3,3-dimethylpent-4-en-2-one, 22 N-benzyl-3-phenylprop-2-enylamine 23 and but-3-enylbenzylamine 24 were prepared according to literature procedures.…”

“…A sample of the purified product was analysed by GC-MS; peak no. 902, β-lactam 11b m/z (relative intensity) 189 (M ϩ , 6), 160 (3), 133 (38), 119 (3), 105 (50), 91 (100), 77 (16), 65 (37), 55 (22), 41 (46), 39 (43), 27 (33); peak no. 908, cis-or trans-N-benzyl-Nbut-2-enylformamide 10b (31% combined cis ϩ trans), 189 (M ϩ , 7), 160 (1), 148 (2), 134 (36), 115 (2), 106 (34), 98 (30), 91 (100), 79 (39), 77 (17), 70 (33), 65 (49), 55 (27), 39 (46), 28 (95); peak no.…”

Small‐Molecule Negative Modulators of Adrenomedullin: Design, Synthesis, and 3D‐QSAR Study

“…An alternative to the Reformatsky reaction is the formation of the ester enolate with a base (lithium cyclohexylisopropylamide (LiCA) is usually the base of choice) followed by addition of the corresponding ketone. [27] Unfortunately, although this procedure gave the desired a-hydroxyester, the yield was less than 10 %, and the whole route was very inefficient. However, this method proved useful in the synthesis of piperazines of type B (Scheme 2).…”

Structural Determination of NSC 670224, Synthesis of Analogues and Biological Evaluation

“…Using the method of Engel and Schexnayder, [18] deprotonation of methyl isobutyrate with LDA and reaction with mono-ethylene glycol protected 1,4-diketocyclohexane gave the corresponding alcohol. After work-up, the crude alcohol was dehydrated with thionyl chloride in pyridine to give alkene 19 in 73% yield over two steps.…”