351:
359:
226:, i.e. the hydrogen adds to the most substituted carbon of the double bond. That the regiochemistry is reverse of a typical HX addition reflects the polarity of the B-H bonds. Hydroboration proceeds via a four-membered transition state: the hydrogen and the boron atoms added on the same face of the double bond. Granted that the mechanism is concerted, the formation of the C-B bond proceeds slightly faster than the formation of the C-H bond. As a result, in the transition state, boron develops a partially negative charge while the more substituted carbon bears a partially positive charge. This partial positive charge is better supported by the more substituted carbon. Formally, the reaction is an example of a
249:
242:
20:
343:
133:
422:
520:. Also called "banana borane", it exists as a dimer. Reactions with 9-BBN typically occur at 60â80 °C, with most alkenes reacting within one hour. Tetrasubstituted alkenes add 9-BBN at elevated temperature. Hydroboration of alkenes with 9-BBN proceeds with excellent regioselectivity. It is more sensitive to steric differences than Sia
284:
olefin, produces generally a mixture of the two organoboranes of comparable amounts, even if the steric properties of the substituents are very different. For such 1,2-disubstituted olefins, regioselectivity can be observed only when one of the two substituents is a phenyl ring. In such cases, such
504:
BH. It also is a dimer. Owing to its steric bulk, it selectively hydroborates less hindered, usually terminal alkenes in the presence of more substituted alkenes. Disiamylborane must be freshly prepared as its solutions can only be stored at 0 °C for a few hours. Dicyclohexylborane
312:
are formed. Often the hydroboration of alkynes use bulky boranes such as 9-BBN to give monoalkenylborane products. The alkenylboranese are susceptible to many reactions such as protonolysis to give the alkene and oxidation to give the aldehyde or ketone.
950:
Kanth, J. V. B.; Brown, H.C. (2001). "Hydroboration. 97. Synthesis of New
Exceptional ChloroboraneâLewis Base Adducts for Hydroboration. DioxaneâMonochloroborane as a Superior Reagent for the Selective Hydroboration of Terminal Alkenes".
862:
Brown, H. C.; Rathke, M.; Rogic, M. M. (1968). "A Fast
Reaction of Organoboranes with Iodine under the Influence of Base. A Convenient Procedure for the Conversion of Terminal Olefins into Primary Iodides via Hydroboration-Iodination".
248:
218:
In extreme cases, such as risubstituted alkenes, hydroboration affords. This significant rate difference in producing di- and tri-alkyl boranes is useful in the synthesis of bulky boranes that can enhance regioselectivity.
726:
Brown, H. C.; Zwefei, G. (1960). "Isomerization of
Organoboranes Derived Addition Mechanism of Isomerization from Branched-Chain and Ring Olefins- Further Evidence for the Elimination-Addition Mechanism of Isomerizaton".
412:
Trialkylboranes react with carbon monoxide to afford homologated products such as 2-bora-1,3-dioxolanes. When the addition of CO is conducted in the presence of a hydride reducing agent, the primary alcohol is produced.
289:-1-phenylpropene, the boron atom is placed on the carbon adjacent to the phenyl ring. The observations above indicate that the addition of H-B bond to olefins is under electronic control rather than steric control.
834:
Brown, H. C.; Lane, C. F. (1970). "The Base-Induced
Reaction of Organoboranes with Bromine. A Convenient Procedure for the Anti-Markovnikov Hydrobromination of Terminal Olefins via Hydroboration-Bromination".
986:
Dodd, D.S.; Ochlschlager, A. C. (1992). "Synthesis of inhibitors of 2,3-oxidosqualene-lanosterol cyclase: conjugate addition of organocuprates to N-(carbobenzyloxy)-3-carbomethoxy-5,6-dihydro-4-pyridone".
350:
358:
493:
Monobromo- and monochloro-borane can be prepared from BMS and the corresponding boron trihalides. The stable complex of monochloroborane and 1,4-dioxane effects hydroboration of terminal alkenes.
342:
627:
373:
when the alkene is trisubstituted. Hydroboration-oxidation is thus an excellent way of producing alcohols in a stereospecific and anti-Markovnikov fashion.
1326:
1038:
819:
322:
539:
are widely used. They also exhibit higher reactivity toward alkynes. Pinacolborane is also widely used in a catalyst-free hydroborations.
327:
As honored by the Nobel Prize to Brown, hydroboration is widely practiced because the alkylboranes are susceptible to many reactions.
1311:
1072:
934:
917:
Dhar, Raj K.; Josyula, Kanth V. B.; Todd, Robert; Gagare, Pravin D.; Ramachandran, Veeraraghavan (2001). "Diisopinocampheylborane".
777:
Allred, E. L.; Sonnenbcrg, J.; Winstcin S. (1960). "Preparation of
Homobenzyl and Homoallyl Alcohols by the Hydroboration Method".
1356:
625:
Hutchins, Robert O.; Cistone, Frank (1981). "Utility and
Applications of Borane Dimethylsulfide in Organic Synthesis. A Review".
890:
Negishi, Ei-Ichi; Brown, Herbert C. (1974). "Thexylborane-A Highly
Versatile Reagent for Organic Synthesis via Hydroboration".
683:
553:
1286:
230:. However, an analysis of the orbitals involved reveals that the reaction is 'pseudopericyclic' and not subject to the
1291:
404:
based reagents such as NIS and NBS are more versatile and do not require rigorous conditions as do organoboranes. etc.
241:
231:
754:
Hudrlik, Paul F.; Hudrlik, Anne M. (1978). "Applications of
Acetylenes in Organic Synthesis". In Patai, Saul (ed.).
1503:
297:
Hydroboration of alkynes gives alkenylboranes. The stereochemistry is cis-addition. With terminal alkynes, both
1482:
1462:
117:
1422:
487:
227:
181:
In terms of synthetic results, diborane or the more conveniently handle BMS and borane-THF are equivalent.
1417:
1296:
152:
136:
809:
1341:
1065:
94:
223:
654:
1351:
1331:
1268:
62:
600:
1321:
1301:
1272:
1259:
448:
235:
98:
19:
1412:
1386:
1316:
370:
68:
1452:
1376:
1366:
1336:
1277:
1034:
968:
930:
815:
679:
336:
83:
79:
27:
1432:
1361:
1346:
1058:
996:
960:
922:
899:
872:
844:
786:
759:
736:
708:
671:
636:
582:
257:
121:
87:
1472:
1442:
1371:
369:
Because the addition of H-B to olefins is stereospecific, this oxidation reaction will be
253:
178:(THF) is also commercially available as THF solutions. Its shelf life is less that BMS.
1467:
1457:
536:
497:
382:
381:
Hydroboration can also lead to amines by treating the intermediate organoboranes with
116:
The development of this technology and the underlying concepts were recognized by the
1497:
1402:
1306:
586:
548:
532:
389:
1477:
1407:
1381:
699:
Kollonitisch, J (1961). "Reductive Ring
Cleavage of Tetrahydrofurans by Diborane".
440:
425:
393:
106:
926:
675:
666:
Zaidlewicz, Marek; Baum, Ofir; Srebnik, Morris (2006). "Borane
Dimethyl Sulfide".
1437:
805:
401:
47:
43:
1447:
1263:
763:
640:
478:
A chiral example is monoisopinocampheylborane. Although often written as IpcBH
132:
110:
972:
139:(BMS) is a complexed borane reagent that is widely used for hydroborations.
97:
that react with a variety of reagents to produce useful compounds, such as
421:
1095:
903:
167:(BMS) is used instead. It can be obtained in highly concentrated forms.
144:
35:
1016:
Hydroboration and Organic Synthesis : 9-Borabicyclo Nonane (9-BBN)
1000:
876:
848:
790:
740:
712:
400:
or iodine. Such reactions have not however proven very popular, because
189:
The stoichiometry of hydroboration of alkenes is ordinarily as follows:
1180:
1146:
1112:
397:
964:
1281:
1231:
1214:
1197:
1163:
1129:
1081:
432:
270:
171:
74:
56:
51:
517:
420:
131:
102:
39:
811:
Advanced Organic Chemistry: Reactions, Mechanisms, and Structure
16:
Addition of a hydrogen-boron bond to C=C, C=N, C=O, or CâĄC bonds
1054:
573:
Brown, H.C. (1961). "Hydroboration-A Powerful Synthetic Tool".
528:
backbone. 9-BBN is more reactive towards alkenes than alkynes.
357:
349:
341:
247:
240:
18:
814:(6th ed.), New York: Wiley-Interscience, p. 822,
256:
to a trialkylborane, showing idealized image of the cyclic
1050:
109:. The most widely known reaction of the organoboranes is
486:. It is obtained by hydroboration of (â)âαâpinene with
222:
In terms of regiochemistry, hydroboration is typically
276:
Hydroboration of 1,2-disubstituted alkenes, such as a
388:
Terminal olefins are converted to the corresponding
354:
Hydroboration-oxidation of (E)-prop-1-en-1-ylbenzene
143:
Much of the original work on hydroboration employed
1395:
1252:
1088:
362:Hydroboration-oxidation of 1-methyl-cyclohex-1-ene
628:Organic Preparations and Procedures International
396:by treating the organoborane intermediates with
509:BH exhibits improved thermal stability than Sia
919:Encyclopedia of Reagents for Organic Synthesis
668:Encyclopedia of Reagents for Organic Synthesis
273:places boron on the less substituted carbon.
1066:
435:) is a rare, easily accessed monoalkylborane.
8:
756:The CarbonâCarbon Triple Bond (1978): Part 1
1073:
1059:
1051:
496:Promient among hindered dialkylboranes is
377:Other C-heteroatom bond forming reactions
1241:
1237:
1224:
1220:
1207:
1203:
1190:
1186:
1173:
1169:
1156:
1152:
1139:
1135:
1122:
1118:
1105:
1101:
865:Journal of the American Chemical Society
837:Journal of the American Chemical Society
729:Journal of the American Chemical Society
335:Treatment of alkylboranes with base and
308:
300:
211:
207:
203:
199:
195:
565:
385:or O-hydroxylaminesulfonic acid (HSA).
346:Regiospecific hydroboration with borane
1033:. Milwaukee, WI: Aldrich Chemical Co.
1031:Organic Syntheses Via Boranes, Vol. 2
7:
1029:Brown, H.C.; Zaidlewicz, M. (2001).
447:), produced by the hydroboration of
439:One example of a monoalkylborane is
601:"The Nobel Prize in Chemistry 1979"
417:Specialty boranes for hydroboration
113:to produce alcohols from alkenes.
14:
524:BH, perhaps because of it rigid C
265:Hydroboration of internal alkenes
1327:HornerâWadsworthâEmmons reaction
323:Hydroborationâoxidation reaction
269:Hydroboration of trisubstituted
366:The net reaction is hydration.
655:Borane-dimethylsulfide complex
1:
1312:CoreyâWinter olefin synthesis
927:10.1002/047084289X.rd248.pub3
676:10.1002/047084289X.rb239.pub2
554:metal-catalysed hydroboration
531:For catalytic hydroboration,
516:A versatile dialkylborane is
989:Journal of Organic Chemistry
953:Journal of Organic Chemistry
779:Journal of Organic Chemistry
587:10.1016/0040-4020(61)80107-5
34:refers to the addition of a
1520:
320:
317:Reactions of organoboranes
1483:Friedel-Crafts Alkylation
1357:RambergâBĂ€cklund reaction
764:10.1002/9780470771563.ch7
641:10.1080/00304948109356130
1287:BamfordâStevens reaction
293:Hydroboration of alkynes
185:Hydroboration of alkenes
118:Nobel Prize in Chemistry
1423:Oxymercuration reaction
1292:BartonâKellogg reaction
1014:Dhillon, R. S. (2007).
488:borane dimethyl sulfide
232:WoodwardâHoffmann rules
228:group transfer reaction
93:Hydroboration produces
1418:Electrophilic addition
1297:Boord olefin synthesis
436:
363:
355:
347:
261:
245:
153:borane dimethylsulfide
140:
137:Borane dimethylsulfide
95:organoborane compounds
23:
1342:Kauffmann olefination
424:
361:
353:
345:
251:
244:
135:
22:
1463:DielsâAlder reaction
1352:Peterson olefination
1332:Hydrazone iodination
1269:Dehydration reaction
904:10.1055/s-1974-23248
1322:Hofmann elimination
1302:Chugaev elimination
1260:Dehydrohalogenation
1001:10.1021/jo00036a008
877:10.1021/ja01020a056
849:10.1021/ja00725a057
804:Smith, Michael B.;
791:10.1021/jo01071a007
741:10.1021/ja01491a058
713:10.1021/ja01467a056
449:tetramethylethylene
252:Hydroboration of a
151:. Usually however,
1387:Cope rearrangement
1317:Grieco elimination
605:www.nobelprize.org
437:
371:diastereoselective
364:
356:
348:
262:
246:
141:
24:
1504:Organic reactions
1491:
1490:
1453:Hydrohalogenation
1377:Olefin metathesis
1367:Takai olefination
1337:Julia olefination
1278:Semihydrogenation
1040:978-0-9708441-0-1
965:10.1021/jo015527o
921:. pp. 1â10.
821:978-0-471-72091-1
758:. London: Wiley.
500:, abbreviated Sia
337:hydrogen peroxide
147:as a source of BH
88:organic compounds
84:organic synthesis
82:is useful in the
80:chemical reaction
28:organic chemistry
1511:
1433:Cyclopropanation
1362:Shapiro reaction
1347:McMurry reaction
1244:
1227:
1210:
1193:
1176:
1159:
1142:
1125:
1108:
1075:
1068:
1061:
1052:
1045:
1044:
1026:
1020:
1019:
1011:
1005:
1004:
983:
977:
976:
947:
941:
940:
914:
908:
907:
887:
881:
880:
859:
853:
852:
831:
825:
824:
801:
795:
794:
774:
768:
767:
751:
745:
744:
723:
717:
716:
701:J. Am. Chem. Soc
696:
690:
689:
663:
657:
651:
645:
644:
622:
616:
615:
613:
611:
597:
591:
590:
570:
482:, it is a dimer
339:gives alcohols:
311:
304:
258:transition state
224:anti-Markovnikov
214:
122:Herbert C. Brown
77:
71:
65:
59:
42:bond to certain
1519:
1518:
1514:
1513:
1512:
1510:
1509:
1508:
1494:
1493:
1492:
1487:
1473:Dehydrogenation
1443:Dihydroxylation
1391:
1372:Wittig reaction
1248:
1243:
1239:
1235:
1226:
1222:
1218:
1209:
1205:
1201:
1192:
1188:
1184:
1175:
1171:
1167:
1158:
1154:
1150:
1141:
1137:
1133:
1124:
1120:
1116:
1107:
1103:
1099:
1084:
1079:
1049:
1048:
1041:
1028:
1027:
1023:
1013:
1012:
1008:
985:
984:
980:
959:(16): 5359â65.
949:
948:
944:
937:
916:
915:
911:
889:
888:
884:
861:
860:
856:
833:
832:
828:
822:
803:
802:
798:
776:
775:
771:
753:
752:
748:
725:
724:
720:
698:
697:
693:
686:
665:
664:
660:
652:
648:
624:
623:
619:
609:
607:
599:
598:
594:
572:
571:
567:
562:
545:
527:
523:
512:
508:
503:
485:
481:
474:
470:
466:
462:
458:
446:
430:
419:
410:
379:
333:
325:
319:
310:
306:
302:
298:
295:
267:
254:terminal alkene
213:
209:
205:
201:
197:
193:
187:
177:
166:
162:
158:
150:
130:
73:
67:
61:
55:
17:
12:
11:
5:
1517:
1515:
1507:
1506:
1496:
1495:
1489:
1488:
1486:
1485:
1480:
1475:
1470:
1468:Wacker process
1465:
1460:
1458:Polymerization
1455:
1450:
1445:
1440:
1435:
1430:
1425:
1420:
1415:
1410:
1405:
1399:
1397:
1393:
1392:
1390:
1389:
1384:
1379:
1374:
1369:
1364:
1359:
1354:
1349:
1344:
1339:
1334:
1329:
1324:
1319:
1314:
1309:
1304:
1299:
1294:
1289:
1284:
1275:
1266:
1256:
1254:
1250:
1249:
1247:
1246:
1229:
1212:
1195:
1178:
1161:
1144:
1127:
1110:
1092:
1090:
1086:
1085:
1080:
1078:
1077:
1070:
1063:
1055:
1047:
1046:
1039:
1021:
1006:
978:
942:
935:
909:
882:
854:
826:
820:
796:
769:
746:
718:
691:
684:
658:
646:
617:
592:
564:
563:
561:
558:
557:
556:
551:
544:
541:
537:catecholborane
525:
521:
510:
506:
501:
498:disiamylborane
483:
479:
476:
475:
472:
468:
464:
460:
456:
444:
428:
418:
415:
409:
408:Carbonylations
406:
390:alkyl bromides
383:monochloramine
378:
375:
332:
329:
321:Main article:
318:
315:
294:
291:
266:
263:
216:
215:
186:
183:
175:
164:
160:
156:
148:
129:
128:Borane adducts
126:
15:
13:
10:
9:
6:
4:
3:
2:
1516:
1505:
1502:
1501:
1499:
1484:
1481:
1479:
1476:
1474:
1471:
1469:
1466:
1464:
1461:
1459:
1456:
1454:
1451:
1449:
1446:
1444:
1441:
1439:
1436:
1434:
1431:
1429:
1428:Hydroboration
1426:
1424:
1421:
1419:
1416:
1414:
1411:
1409:
1406:
1404:
1403:Hydrogenation
1401:
1400:
1398:
1394:
1388:
1385:
1383:
1380:
1378:
1375:
1373:
1370:
1368:
1365:
1363:
1360:
1358:
1355:
1353:
1350:
1348:
1345:
1343:
1340:
1338:
1335:
1333:
1330:
1328:
1325:
1323:
1320:
1318:
1315:
1313:
1310:
1308:
1307:Cope reaction
1305:
1303:
1300:
1298:
1295:
1293:
1290:
1288:
1285:
1283:
1279:
1276:
1274:
1270:
1267:
1265:
1261:
1258:
1257:
1255:
1251:
1233:
1230:
1216:
1213:
1199:
1196:
1182:
1179:
1165:
1162:
1148:
1145:
1131:
1128:
1114:
1111:
1097:
1094:
1093:
1091:
1087:
1083:
1076:
1071:
1069:
1064:
1062:
1057:
1056:
1053:
1042:
1036:
1032:
1025:
1022:
1017:
1010:
1007:
1002:
998:
994:
990:
982:
979:
974:
970:
966:
962:
958:
954:
946:
943:
938:
936:9780470842898
932:
928:
924:
920:
913:
910:
905:
901:
897:
893:
886:
883:
878:
874:
870:
866:
858:
855:
850:
846:
842:
838:
830:
827:
823:
817:
813:
812:
807:
800:
797:
792:
788:
784:
780:
773:
770:
765:
761:
757:
750:
747:
742:
738:
734:
730:
722:
719:
714:
710:
706:
702:
695:
692:
687:
681:
677:
673:
669:
662:
659:
656:
650:
647:
642:
638:
634:
630:
629:
621:
618:
606:
602:
596:
593:
588:
584:
580:
576:
569:
566:
559:
555:
552:
550:
549:Carboboration
547:
546:
542:
540:
538:
534:
533:pinacolborane
529:
519:
514:
499:
494:
491:
489:
454:
453:
452:
450:
442:
434:
427:
423:
416:
414:
407:
405:
403:
399:
395:
394:alkyl iodides
391:
386:
384:
376:
374:
372:
367:
360:
352:
344:
340:
338:
330:
328:
324:
316:
314:
292:
290:
288:
283:
279:
274:
272:
264:
259:
255:
250:
243:
239:
237:
233:
229:
225:
220:
192:
191:
190:
184:
182:
179:
173:
168:
154:
146:
138:
134:
127:
125:
123:
119:
114:
112:
108:
107:alkyl halides
104:
100:
96:
91:
89:
85:
81:
76:
70:
64:
58:
53:
49:
45:
41:
37:
33:
32:hydroboration
29:
21:
1478:Ene reaction
1427:
1408:Halogenation
1382:Ene reaction
1253:Preparations
1030:
1024:
1015:
1009:
995:(10): 2794.
992:
988:
981:
956:
952:
945:
918:
912:
898:(2): 77â89.
895:
891:
885:
871:(18): 5038.
868:
864:
857:
843:(22): 6660.
840:
836:
829:
810:
806:March, Jerry
799:
782:
778:
772:
755:
749:
732:
728:
721:
704:
700:
694:
667:
661:
649:
635:(3â4): 225.
632:
626:
620:
608:. Retrieved
604:
595:
578:
574:
568:
530:
515:
495:
492:
477:
441:thexylborane
438:
426:Thexylborane
411:
387:
380:
368:
365:
334:
326:
296:
286:
281:
277:
275:
268:
238:reactivity.
221:
217:
188:
180:
169:
142:
115:
92:
48:triple bonds
31:
25:
1438:Epoxidation
1018:. Springer.
707:(6): 1515.
575:Tetrahedron
402:succinimide
198:+ 3 RCH=CH
1448:Ozonolysis
1264:haloalkane
685:0471936235
581:(3): 117.
560:References
307:HB(CH=CHR)
236:pericyclic
155:complex BH
50:involving
1413:Hydration
1396:Reactions
892:Synthesis
331:Oxidation
111:oxidation
1498:Category
973:11485456
808:(2007),
735:: 1504.
610:21 March
543:See also
202:â B(CH
145:diborane
99:alcohols
78:). This
36:hydrogen
1273:alcohol
1181:Heptene
1147:Pentene
1113:Propene
1089:Alkenes
1082:Alkenes
398:bromine
271:alkenes
1282:alkyne
1232:Decene
1215:Nonene
1198:Octene
1164:Hexene
1130:Butene
1096:Ethene
1037:
971:
933:
818:
785:: 25.
682:
463:+ 2 Me
443:(ThxBH
433:methyl
431:(Me =
303:BCH=HR
172:adduct
103:amines
72:, and
52:carbon
44:double
1280:from
1271:from
1262:from
518:9-BBN
467:C=CMe
287:trans
282:trans
105:, or
40:boron
1035:ISBN
969:PMID
931:ISBN
896:1974
816:ISBN
680:ISBN
653:See
612:2017
535:and
513:BH.
392:and
305:and
234:for
170:The
159:S(CH
46:and
997:doi
961:doi
923:doi
900:doi
873:doi
845:doi
787:doi
760:doi
737:doi
709:doi
672:doi
637:doi
583:doi
505:Chx
471:â
285:as
280:or
278:cis
206:âCH
124:.
120:to
90:.
86:of
75:CâĄC
69:C=O
63:C=N
57:C=C
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1500::
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1225:18
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705:83
703:.
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633:13
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603:.
579:12
577:.
490:.
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194:BH
174:BH
101:,
66:,
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1234:(
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1223:H
1221:9
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1217:(
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1204:8
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1200:(
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1183:(
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1170:6
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1166:(
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1153:5
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1149:(
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1136:4
1134:C
1132:(
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1123:6
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1119:3
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1115:(
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455:B
445:2
429:2
309:2
301:2
299:H
260:.
212:3
208:2
204:2
200:2
196:3
176:3
165:2
163:)
161:3
157:3
149:3
54:(
38:-
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